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AMOS Terminal System User`s Guide

1. 14 7 14 1 2 9 Variable Speed Scroll Commands 14 7 14 1 2 10 Split Screen Commands 14 7 14 1 2 11 Block Fill Commands 14 8 14 1 2 12 Box Commands 14 8 14 1 2 13 Alternate Page Commands 14 8 14 1 2 14 Color Commands 14 8 14 1 2 15 Miscellaneous Commands 14 9 14 2 RESERVED CODES i aici Ses vuU Dec SOA AM whi Awad SOL EID 14 9 CHAPTER 15 TERMINAL CONTROL COMMANDS CHAPTER 16 ASSEMBLY LANGUAGE TERMINAL DRIVERS 16 1 TERMINAL DRIVER STRUCTURE 16 1 16 1 1 The Terminal Driver Header 16 1 16 1 1 1 The Type Control Bits TD TYP 16 2 16 1 1 2 The Input Routine Transfer Vector TD INP 16 2 16 1 1 3 The Output Routine Transfer Vector TD OTP 16 2 16 1 1 4 The Echo Routine Transfer Vector TD ECH 16 2 16 1 1 5 The TCRT Routine Transfer Vector TD CRT 16 2 16 1 1 6 The Initialization Routine Transfer Vector TD INI 16 2 16 1 1 7 The Impure Area Size TD IMP 16 3 16 1 1 8 The Row and Columns Sizes TD ROW and TD COL 16 3 16 1 1 9 The Terminal Capabilities Word TD FLG 16 3 16 1 1 10 The TRMCHR Routine Transfer Vector TD TCH 16 4 16 1 2 The Termina
2. 9 2 9 3 USING FUNCTION KEYS WITHIN YOUR APPLICATIONS SOFTWARE 9 3 CHAPTER 10 PROGRAMMING COLOR TERMINALS 10 1 THE IMPACT OF COLOR ssssssssese ses 10 1 10 2 SELECTING COLORS WITH SOFTWARE 10 1 10 3 USING FOREGROUND AND BACKGROUND COLOR SELECTION 10 1 10 3 1 Selecting Foreground 10 2 10 3 2 Selecting Background Color 10 2 10 3 3 Dealing with Color and Non Color Terminals 10 2 10 3 4 Combining Color and Other Display Attributes 10 2 10 3 5 Maintaining the Default Foreground and Background Colors 10 3 10 4 USING AM 70 COMPATIBLE COLOR 10 3 CHAPTER 11 USING THE ALTERNATE CHARACTER SET 11 1 USING THE ALTERNATE CHARACTER SET 11 1 11 2 THE LINE DRAWING CHARACTERS 11 2 11 3 THE BLOCK GRAPHICS CHARACTERS 11 2 11 4 THE WORD PROCESSING 11 3 11 5 DEALING WITH CHARACTERS WHICH ARE NOT PRESENT 11 3 CHAPTER 12 USING THE PRINTER PORT 12 1 SCREEN PRINT ERA CE URGE M ES 12 1 12 2 TRANSPARENT PRINT iu weed ceri Me need eie 12 2 CHAPTER 13 MISCELLANEOUS FEATURES 134 BLOCK FILE ud atest arent ued ahs tae PC Peel EROR RE 13 1 13 2
3. 1 2 1 2 2 One Application Several Terminals 1 2 1 2 3 Many Terminals One 1 2 1 8 THE PHILOSOPHY OF TERMINAL DEVICE INDEPENDENCE 1 3 1 4 THE PHILOSOPHY BEHIND ALPHA MICRO TERMINAL SOFTWARE 1 3 1 4 1 Dealing with the Compromises 1 4 1 4 2 Dealing with Feature Differences 1 5 1 5 RELATED DOCUMENTATION sssssese s 1 5 CHAPTER 2 HOW AMOS INTERFACES TO TERMINALS 2 1 THE HARDWARE INTERFACE ssssses e 2 1 2 2 INTERFACE DRIVERS ine EA Re SER PEE a dal 2 1 2 3 TERMINAG DRIVERS ew wheveugddeb 3i Reka pew eaa 2 2 2 4 STANDARDIZED TERMINAL INTERFACE 2 2 2 4 1 The Monitor TCRT Calls 2 2 2 4 2 The TRMCHR 2 3 2 4 3 Higher Level Language Interfaces to the Terminal 2 3 CHAPTER 3 INTRODUCTION TO TERMINALS 3 1 CONVERSATIONAL VS BLOCK MODE 3 1 3 2 FIELD VS MODE TERMINALS sssssssesses n 3 1 3 2 1 Compatibility 15 3 2 3 2 1 1 To Space or Not to Space 3 2 2 2 1 2 S creen Flash se Peale ow ea 3 2 CHAPTER 4 PRINCIPLES OF EFFECTIVE SCREEN DESIGN 4 1 WHAT WE ARE LOOKING FOR
4. 15 36 Terminal Control Commands 15 127END STATUS LINE TCRT 1 129 This command is used to terminate any of the status line functions It must be used after sending the desired text to the status line to return the terminal to its normal text area display Details on the use of status lines can be found in Chapter 8 This function is available only if the TD STS bit is set in the terminal capabilities flags 15 128SELECT UNSHIFTED STATUS LINE W O ADDRESS TCRT 1 130 This function allows you to send text to the unshifted bottom status line Immediately after issuing this command send the text you wish displayed on the status line followed by an End Status Line TCRT 1 129 command Details on the use of status lines can be found in Chapter 8 This command is similar to the TCRT 1 54 command but only allows writing to the entire status line without individually addressable columns This makes this command less efficient than the TCRT 1 54 command but it is supported by a wider variety of terminals The size of the status line referenced by this command may be found via the TRMCHR monitor call This function is available only if the TD STS bit is set in the terminal capabilities flags 15 129SELECT SHIFTED STATUS LINE W O ADDRESS TCRT 1 131 This function allows you to send text to the shifted bottom status line Immediately after issuing this command send the text you wish displayed on the status line follow
5. Terminal System User s Guide ALPHA MICROS YSTEMS RIGHT FROM THE ST DSS 10096 00 A01 1995 Alpha Microsystems REVISIONS INCORPORATED REVISION DATE A00 March 1987 A01 June 1996 AMOS Terminal System User s Guide To re order this document request part number DSS 10096 00 The information contained in this manual is believed to be accurate and reliable However no responsibility for the accuracy completeness or use of this information is assumed by Alpha Microsystems This document may contain references to products covered under U S Patent Number 4 530 048 The following are registered trademarks of Alpha Microsystems Santa Ana CA 92799 AMIGOS AMOS Alpha Micro AlphaACCOUNTING AlphaBASIC AlphaCALC AlphaCOBOL AlphaDDE AlphaFORTRAN 77 AlphaLAN AlphaLEDGER AlphaMAIL AlphaMATE AlphaNET AlphaPASCAL AlphaRJE AlphaWRITE CASELODE OmniBASIC VER A TEL VIDEOTRAX The following are trademarks of Alpha Microsystems Santa Ana CA 92799 AlphaBASIC PLUS AlphaVUE AM PC AMTEC DART ESP MULTI inSight am inFront am All other copyrights and trademarks are the property of their respective holders ALPHA MICROSYSTEMS 2722 S Fairview St P O Box 25059 Santa Ana CA 92799 TABLE OF CONTENTS CHAPTER 1 INTRODUCTION 1 1 A STATEMENT OF THE PROBLEM 1 1 1 2 SOME POSSIBLE SOLUTIONS 1 2 1 2 1 One Application One Terminal
6. 13 4 14 8 box scrolling iom he ees es Le 13 4 14 8 brightness nti ed 5 7 British Pound character 15 46 character block fill 13 1 Character display 15 48 Ghar cter Set 142 5 ace datura bets 15 48 character sets 11 1 to 11 3 chromatic color 5 6 amp lear screen 15 1 clear to end of line 15 3 clear to end of screen 15 3 codes COVINA rune Cx ran ce x e B 2 horizontal size B 6 eyed Be eee e Beech B 2 status line attributes B 3 VEMMICAl SIZE iure EL Ea B 6 E 4 8 5 1 10 1 achromatic 5 6 additive mixture 5 14 Alpha Micro map 5 17 C 1 AM E70 mode i ise eis aeg ced 10 3 AM 70 mode selection 15 36 to 15 40 attributes kno rex EE Se 10 2 background 10 1 to 10 2 15 50 best combinations 5 8 Chromatic 5 6 CodeS 4 cognitive guidelines 5 12 cognitive principles 5 9 contextual ieceri asa iania 5 7 data grouping 5 9 description eee eee
7. 6 SCREEN DISPLAY ATTRIBUTES 6 1DIM INTENSITY The dim attribute causes text to be displayed in dim or reduced intensity mode Unlike the other screen attributes the dim attribute is always a mode attribute with hidden attributes That is it behaves like a mode terminal and does not require a screen position to switch from bright to dim or back again You start writing text in dim mode by issuing a TCRT 1 11 and end it by issuing a 1 12 command Dim mode text is an important part of protected fields which are discussed in detail in Chapter 7 Color terminals vary in the way that they handle the display of dim characters Some actually choose a dimmer version of the currently selected foreground color while others substitute an entirely different color Care should be taken in using the dim attribute on color displays unless the behavior of the terminal to be used is known 6 2UNDERLINE Text written with the underline attribute is displayed with a line underneath it Underline mode is selected by the TCRT 1 30 command and disabled with the TCRT 1 31 command The screen position occupied by the begin attribute command is displayed as a normal space with no attributes The underlining does not take affect until the next character Likewise the end underline command is displayed as a normal space with no underlining If your terminal supports hidden attributes the T NSP bit in the TRMCHR characteristics word is se
8. 15 TERMINAL CONTROL COMMANDS The key to the terminal independence offered by AMOS is a set of terminal control functions which perform the same function and have the same effect on the terminal screen regardless of the characteristics of the terminal being used Because of the wide variety of terminals and their broad range of capabilities in addition to the standard terminal functions which all terminals are assumed to have a number of the commands described below may or may not be present on a particular terminal In these cases the command is either ignored where this will have no material effect on the screen display or are enabled by a flag that tells a program that a particular feature is present These flags may be obtained for the terminal that is currently in use via the TRMCHR assembly language monitor call or the TRMCHR XCALL subroutine for AlphaBASIC users It is the responsibility of the program to check these flags and not use any feature that does not have its corresponding flag set Using a feature that does not have its flag set will result in unpredictable results ranging from visually unpleasant displays to locking up crashing the terminal 15 1CLEAR SCREEN TCRT 1 0 This call clears the current terminal screen segment and positions the cursor at row 1 column 1 Because some terminals require an extended period of time to clear the screen the terminal driver may follow the clear screen code with a series o
9. Word specifying the currently selected foreground color Zero is returned for monochrome terminals Word specifying the currently selected background color Zero is returned for monochrome terminals Word specifying the number of rows in the currently selected window This field is only valid when the MULTI window based environment manager is in use Word specifying the number of columns in the currently selected window This field is only valid when the MULTI window based environment manager is in use If the TC BMP flag is set in D2 indicating that the user has requested the TCRT feature availability bitmap the TRMCHR routine must also return the following field TC BMP A 32 byte table describing the TCRT codes in the 1 n set For each of the 256 TCRT codes a corresponding bit is set if the TCRT call is available If the TCRT call is not available the bit will be zero Bits are assigned starting at the first byte in the table with the low order bit bit 0 corresponding to TCRT 1 0 the next bit bit 1 corresponding to TCRT 1 1 etc 16 2EMULATING FEATURES NOT AVAILABLE ON YOUR TERMINAL If a given terminal does not support a certain capability the normal course of action is to simply omit the feature adjusting the capabilities flags and TCRT bitmap accordingly While this should be sufficient to alert applications software to the lack of the feature there are times when the results acheived by this are not fully
10. 0000 0 cece eee eee eee 4 1 42 THE REAL WORLD lt c3 0 sexa a aed pa 4 2 4 3 THE WELL DESIGNED SCREEN 0000s 4 2 4 4 THE HUMAN CONSIDERATIONS 2 0 00 eee ee eee 4 3 4 4 1 Human Characteristics Important to Screen Design 4 3 4 4 2 Screen Format and 4 4 4 5 HARDWARE CONSIDERATIONS 4 6 4 5 1 Blinking TE sich rege e E RR RC RR HR IG 4 7 4 5 2 Different Brightness 2 2 raees eee 4 7 4 5 3 Reverse Video nne 4 7 45 4 nderlintrig zc eiu E Pes Ew Re YES ee 4 7 4 5 5 132 Column 5 4 7 4 5 6 Status ENES zc Ge eb euet rA evo rre 4 8 AMOS Terminal System User s Guide Page iv AMOS Terminal System User s Guide 4 5 7 Split Screen sessi Rr Rr RR RR 4 8 4 5 960l0E rots Cox imde aotem ye levem EN Se CERA ake 4 8 4 59 GEaphleSie e eremo Re etiem obe hie eE ER 4 8 4 6 IMPLEMENTING GOOD SCREEN DESIGNS 4 8 CHAPTER 5 USING COLOR EFFECTIVELY 5 1 THE IMPACT OF COLOR rh 5 1 5 2 THE PHYSIOLOGY OF COLOR 000000 n 5 2 5 21 he bens ss crecer ed Wek Goud Sel e ESSI 5 3 5 2 2 I he Retlnia sb i ttes reete a eee Gad he ais 5 3 5 2 3 After th
11. 15 177SELECT DEFAULT CHARACTER SET TCRT 1 179 VERSION 2 00 AND LATER Primarily used by the VPC Coprocessor for PC Terminal operation this call returns the terminal to the character set selected in Setup Mode 15 178SELECT PC TERMINAL EMULATION TCRT 1 180 VERSION 2 00 AND LATER Primarily used by the VPC Coprocessor for PC Terminal operation this call selects Scan Code keyboard and 25 line display with no bottom status line 15 179SELECT ASCII TERMINAL OPERATION TCRT 1 181 VERSION 2 00 AND LATER Primarily used by the VPC Coprocessor to exit PC Terminal operation this call selects ASCII keyboard encoding and 24 line display with top and bottom status lines 15 180SELECT AUX PORT HOST TCRT 1 182 VERSION 2 00 AND LATER The Aux port on the terminal is enabled for host communication This command has the same effect as using the P command in Setup Mode to set the Aux port For more information on the AM 65 s serial ports see the AM 65 Reference Guide 15 181SELECT MAIN PORT HOST TCRT 1 183 VERSION 2 00 AND LATER The Main port on the terminal is enabled for host communication This command has the same effect as using the P command in Setup Mode to set the Main port For more information on the AM 65 s serial ports see the AM 65 Reference Guide 15 182TOGGLE HOST PORTS TCRT 1 184 VERSION 2 00 AND LATER This call toggles between Main and Aux ports for host communication This command has the same effect as us
12. Shift Out SI 017 15 OF Shift In DLE 020 16 10 Data Link Escape DC1 021 17 11 Device Control 1 DC2 022 18 12 Device Control 2 DC3 023 19 13 Device Control 3 DC4 024 20 14 Device Control 4 NAK 025 21 15 Negative Acknowledge SYN 026 22 16 Synchronous Idle ETB 027 23 17 End of Transmission Blocks CAN 030 24 18 Cancel EM 031 25 19 End of Medium AMOS Terminal System User s Guide 2 CHARACTER OCTAL nU 032 033 034 035 036 037 040 041 042 043 044 045 046 047 050 051 052 053 054 055 056 057 060 061 062 063 064 065 066 067 070 071 072 073 074 075 076 077 100 101 102 103 104 105 106 107 110 111 112 113 114 PRINTING CHARACTERS DECIMAL HEX 26 1A 27 1B 28 1C 29 1D 30 1E 31 1F 32 20 33 21 34 22 35 23 36 24 37 25 38 26 39 27 40 28 41 29 42 2A 43 2B 44 2C 45 2D 46 2E 47 2F 48 30 49 31 50 32 51 33 52 34 53 35 54 36 55 37 56 38 57 39 58 3A 59 3B 60 3C 61 3D 62 3E 63 3F 64 40 65 41 66 42 67 43 68 44 69 45 70 46 71 47 72 48 73 49 74 4A 75 4B 76 4 ASCII Character Chart MEANING Special Sequence Escape File Separator Group Separator Record Separator Unit Separator Space Exclamation Mark Quotation Mark Number Sign Dollar Sign Percent Sign Ampersand Apostrophe Opening Parenthesis Closing Parenthesis Asterisk Plus Comma Hyphen or Minus Period Slash
13. eAll information from the user is accepted from the central portion of the screen ePrompts are not displayed until the information is actually requested einformation supplied to a question is left on the screen to remind the user of previous responses which may affect the choice of later responses eAny time that a response is requested the range of valid responses is given to the user on the bottom portion of the screen in a standard consistent format Error messages are only generated when the user s input is ambiguous Even if a typo is present if the input cannot be mistaken for a different command the command is executed with no error message eError messages are displayed in blinking text at the bottom of the screen eAll error messages display both the cause of the error and suggestions on how to rectify the problem ewWhen a fill in the blanks type of screen display is presented the user is free to move back and forth from field to field until satisfied with all answers The use of the upper status line is limited to non essential information in case it is not available or its use is preempted by other software eCommand prompts where the expected response is a keyword selected from a displayed list display all possible responses The keyword is displayed as bright text while the explanatory text is displayed in reduced intensity This focuses attention on the keywords while providing additional information in
14. reduced intensity normal intensity start blink field end blink field set terminal attributes start underscore end underscore start reverse video end reverse video start reverse blink end reverse blink start underscore blink end underscore blink start underscore reverse end underscore reverse start underscore reverse blink end underscore reverse blink start underscore w o space end underscore w o space start reverse w o space end reverse w o space 14 6 14 1 2 4Status Line Commands TCRT 1 110 TCRT 1 111 TCRT 1 112 TCRT 1 113 TCRT 1 114 TCRT 1 115 TCRT 1 116 TCRT 1 117 TCRT 1 118 TCRT 1 119 TCRT 1 54 TCRT 1 55 TCRT 1 63 TCRT 1 128 TCRT 1 129 TCRT 1 130 TCRT 1 131 AMOS Monitor TCRT Codes start reverse blinking w o space end reverse blinking w o space start underscore blinking w o space end underscore blinking w o space start underscore reverse w o space end underscore reverse w o space start underscore reverse blink w o space end underscore reverse blink w o space start blink w o space end blink w o space send message to unshifted bottom status line send message to shifted bottom status line send message to top status line select top status line w o address end status line select unshifted status line w o addr select shifted status line w o addr 14 1 2 5Graphics Character Set Commands and Characters TCRT 1 23 TCRT 1 24 TCRT 1 38 TCRT 1
15. 13 3 15 34 to 15 35 15 2 15 42 2 1 E 1 9 1 9 3 9 1 to 9 2 D 1 13 4 11 2 15 11 to 15 14 15 46 3 2 15 29 to 15 34 5 16 to 5 18 Page Index 4 AMOS Terminal System User s Guide MONG ul A Ee 15 1 horizontal size codes B 6 Dile ssa Rest ds 5 6 5 16 humaneye ee 5 2 CONES Rae he ei dees 5 3 edge discrimination 5 3 individual characteristics 5 8 IONS dedo haa Gas She aes ERN 5 3 optic nerve 5 4 photopigment 5 4 photopigments 5 3 retina sos oxi DA tee des ea 5 3 a det 5 3 human learning 4 4 human memory 4 4 2 1 insert character 13 3 15 5 insert column 13 3 15 23 insert line fae SEN Es eee y EY 13 3 15 4 interface ueste mech Ay eg tuns 2 1 standardized terminal 2 2 interface drivers 2 1 jump scroll 13 5 15 25 keyboard lock 15 2 keyboard mode 15 49 keyboard unlock 15 8 Less than or Equal character 15 46 lightniess zs ces ta Dane RRT o 5 6 to 5 7 5 16 line drawing 6
16. This call disables the reverse video text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 33 command but does not occupy a screen position AMOS Terminal System User s Guide Terminal Control Commands Page 15 31 This function is available only if the TD RVA and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 111START REVERSE VIDEO BLINKING TEXT W O A SPACE TCRT 1 110 This call enables the reverse video and blinking text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 34 function but does not occupy a screen position This functi
17. 0 eee eee 11 2 Linefeed character 15 45 local printer 2 0 0 02 cee eee eee 14 7 lock keyboard 15 2 Mail port e ret hts 15 48 mode terminals 3 1 to 3 2 modes blOCKz eei et a teas Bad 3 1 conversational 3 1 multi page terminals 13 2 New Line 15 45 Not Equal character 15 46 opponent channels 5 4 to 5 5 PC terminal emulation 15 47 perception ea ka EEEE 4 3 5 5 PER i a RON REA 9 1 PIICHaracter cy ses Eee iet vetet ce sa 15 46 AMOS Terminal System User s Guide AMOS Terminal System User s Guide Plus or Minus character print screen printer port screen print transparent print Printing Bidirectional protected fields read character at cursor read cursor address reduced intensity reflection Restore area retinal channels return reverse video RGB system row codes saturation Save area screen clearing Screen design screen flash screen format screen off screen on scroll rate scrolling Select ASCII terminal operation Select default character set Select PC terminal emulation serial interface Set terminal time smooth scroll special characters split screen standards ANSI X3 64 status lines attributes emulation TCRT calls reserved TCRT codes by fu
18. 0 0 000 0 000 Black 0 1 000 0 000 White 0 0 500 1 000 Blue 60 0 500 1 000 Magenta 120 0 500 1 000 Red 180 0 500 1 000 Yellow 240 0 500 1 000 Green 300 0 500 1 000 Cyan 0 0 333 0 000 Charcoal gray 0 0 667 0 000 Light gray 0 0 334 1 000 Deep blue 60 0 334 1 000 Deep magenta 120 0 334 1 000 Deep red 180 0 334 1 000 Yellow brown 240 0 334 1 000 Deep green 300 0 334 1 000 Light blue 0 0 500 0 334 Violet blue 0 0 834 0 200 Light blue 2 0 0 167 1 000 Navy blue 60 0 167 1 000 Violet 120 0 167 1 000 Brick red 180 0 167 1 000 Yellow green 240 0 167 1 000 Forest green 300 0 167 1 000 Blue gray 1 240 0 500 0 334 Blue green 240 0 834 0 200 Very light blue 20 0 500 1 000 Medium blue 40 0 500 1 000 Purple 100 0 500 1 000 Hot pink 200 0 500 1 000 Chartreuse 260 0 500 1 000 Foam green 280 0 500 1 000 Pea green 120 0 500 0 334 Pale burgundy 300 0 500 0 334 Blue gray 2 340 0 500 1 000 Hot blue 80 0 500 1 000 Pink 140 0 500 1 000 Red orange 160 0 500 1 000 Amber 220 0 500 1 000 Light green 1 320 0 500 1 000 Sky blue 120 0 834 0 200 Purple 300 0 834 0 200 Light cyan 2 0 0 667 0 500 Faded blue 60 0 667 0 500 Pale purple 120 0 667 0 500 Pale hot pink 180 0 667 0 500 Pale yellow 240 0 667 0 500 Sea foam green AMOS Terminal System User s Guide The Alpha Micro Color Map Page C 3 Table C 1 cont d The Alpha Micro Color Map Color Number R G B 47 0 33 1 00 1 00 48 0 67 0 33 0 67 49 1 00 0 67 1 00 50 0 33 0 00 0 67 51 0 67 0 33 1 00
19. 1 23 has been issued Command Code Symbol Displayed 1 38 Top left corner 1 39 Top right corner 1 40 Bottom left corner 1 41 Bottom right corner 1 42 Top intersection 1 43 Right intersection 1 44 Left intersection 1 45 Bottom intersection 1 46 Horizontal line 1 47 Vertical line 1 48 Center intersection 1 49 Solid block 1 50 Slanted line block 1 51 Cross hatch block 1 52 Double horizontal line 1 53 Double vertical line 1 49 Solid block 1 50 Slanted line block 1 51 Cross hatch block 1 64 Up arrow 1 65 Down arrow 1 66 Raised dot 1 67 End of line marker 1 68 Horizontal tab symbol 1 69 Paragraph symbol 1 70 Dagger symbol 1 71 Section symbol 1 72 Cent sign 1 73 One quarter symbol 1 74 One half symbol 1 75 Degree symbol 1 76 Trademark symbol 1 77 Copyright symbol 1 78 Registered symbol AMOS Terminal System User s Guide 6 Code Summaries Table B 5 Horizontal and Vertical Size Codes vertical size in rows h horizontal size in columns vorh ASCII vorh ASCII vorh ASCII Character Character Character 1 45 M 89 y 2 46 90 2 3 47 91 4 48 P 92 5 96 49 Q 93 6 amp 50 R 94 7 51 S 95 DEL 8 52 T 96 Y 9 53 U 97 Y 10 54 V 98 Y 11 55 W 99 Y 12 56 X 100 Y 13 57 Y 101 Y amp 14 58 2 102 Y 15 59 103 Y 16 0 60 104 Y 17 1 61 105 Y 1
20. 10 5 1THE IMPACT OF COLOR After many years of being an expensive option available on only very high end computer systems color terminals are declining in price to the point where they are readily affordable for a wide variety of applications Just as color film brought a new sense of life to photography and greatly increased the number of applications to which it could be put color can bring many important benefits to the user of a computer terminal By coding data and prompts with color the screen display can be made easier to comprehend and interpret An important figure that might otherwise be lost in a screenful of numbers can be made to stand out and attract attention However just as it can help the comprehension of a display so can it confuse Improper use of colors in combination can lead to eyestrain and reduced operator efficiency Inappropriate choices of colors can cause an operator to jump to the wrong conclusion about a display making the use of color misleading instead of helpful Additionally the addition of color to our already confusing world of incompatible terminals creates a whole host of new problems relating to the number of available colors how to describe them and how to specify them within a program Color can be an important addition to software helping in both its usability and saleability but only if the proper attention is paid to the physical physiological and psychological aspects of color Unfortu
21. 15 45 VPC 15 47 Window style box 15 42 word processing characters 11 3 X3 64 standard 1 3 sed tacita ice ete Did 15 1 AMOS Terminal System User s Guide
22. AMOS Terminal System User s Guide 1 2 Introduction Thus we have our problem how do we create software which takes advantage of the power of the very latest terminal without forcing ourselves to constantly rewrite our software at every turn As we will see throughout this book this is not a simple problem to solve although it does have a rather elegant solution 1 280ME POSSIBLE SOLUTIONS Given a problem of this size and importance it is not surprising that many different groups have tried to devise a solution For purposes of illustration let s go through a few of the solutions that have been attempted 1 2 10ne Application One Terminal Certainly the most straightforward of the possible solutions is simply to restrict a given software package to one terminal This has been most popular with software vendors that also sell terminals for obvious reasons It has not met with a great deal of success however because not only are the users of the software package denied the opportunity to take advantage of the latest in terminal technology the vendor of the software package is also unable to take advantage of it The software package therefore quickly becomes obsolete 1 2 20ne Application Several Terminals The next approach is to create the software package such that it can take advantage of two or three or up to 20 or more different terminals This is typically done by actually coding into the application package
23. Assembly Language Terminal Drivers The output routine signals to the rest of the terminal service system what action is to be taken by setting the condition code flags prior to returning to the terminal service system The following settings are valid Z bitset ignore this character N bitset output this character and adjust output position this is the normal case allbitsreset output this character but do not adjust output position Because the output routine is called at interrupt level the routine does not have a job context and is restricted as to the monitor calls it can issue Specifically you cannot issue SLEEP TTY or any other call requiring a job context In addition because this routine is being executed at interrupt level it is vital that it be made as efficient as possible to avoid adverse impact on system performance 16 1 5The Terminal Driver TCRT Routine The TCRT routine of the terminal driver receives all TCRT calls and is resposible for translating the specific TCRT call to the series of characters required to invoke the command on the terminal While this action normally consists of looking up the function in a table of character sequences the TCRT routine can perform almost any type of computation to detarmine the proper seqeuence When the TCRT routine is called the following registers will be set up D1 Contains the TCRT command exactly as specified by the user A5 Indexes the terminal control block for
24. PART V CREATING A TERMINAL DRIVER PROGRAM AMOS Terminal System User s Guide 16 ASSEMBLY LANGUAGE TERMINALDRIVERS 16 1TERMINAL DRIVER STRUCTURE The terminal driver is comprised of a header area containing descriptive information and subroutine dispatches and a set of subroutines which implement special terminal driver functions Terminal drivers are stored in DSKO 1 6 The source to sample terminal drivers can be found on the standard AMOS release in account DSKO 10 2 16 1 1The Terminal Driver Header The terminal driver header contains both descriptive information describing the particular terminal driver and its characteristics and subroutine dispatches which allow the terminal service system to transfer control to the terminal driver support routines The terminal driver header is structured as follows TD TYP word Type control bits TD INP word Branch to the input routine TD OTP word Branch to the output routine TD ECH word Branch to the echo routine TD CRT word Branch to the TCRT routine TD INI word Branch to the initialization routine TD IMP word Number of impure bytes to allocate TD ROW byte Obsolete TD COL byte Obsolete TD FLG Terminal capability flags TD TCH word Branch to TRMCHR routine AMOS Terminal System User s Guide 16 2 Assembly Language Terminal Drivers 16 1 1 1The Type Control Bits TD TYP This word contains a number of single bit flags describing the overall
25. SPLI SGREENS heiter ited ead equae nns fh eal dot cans 13 1 TSS ALTERNATE PAGE vex oe Rr XD Were nares 13 2 13 4 CURSOR SHAPE CONTROL 13 3 13 9 VIDEO ENABEE DISABLEE cirio Lhnsemermee Pai Moka ee Tada 13 3 13 6 INSERT DELETE LINE CHARACTERS AND COLUMNS 13 3 19 7 BOX COMMANDS faci aoa ER Oh aon De we CRI RS 13 4 13 7 1 Drawing Boxes ns 13 4 19 7 2 ScrollitigBOX8S ehh eae Ea 13 4 13 8 VARIABLE SCROLL RATES 0 0 0 0 13 5 AMOS Terminal System User s Guide Page vi AMOS Terminal System User s Guide CHAPTER 14 AMOS MONITOR TCRT CODES 14 1 INDEX TO QUICK REFERENCE 14 1 14 1 1 TCRT Codes by Number 14 1 14 1 2 TCRT Codes by Function 14 5 14 1 2 1 Cursor Positioning Commands 14 5 14 1 2 2 Screen Clearing Commands 14 5 14 1 2 3 Display Attribute Commands 14 5 14 1 2 4 Status Line Commands 14 6 14 1 2 5 Graphics Character Set Commands and Characters 14 6 14 1 2 6 Protected Field Commands 14 7 14 1 2 7 Local Printer Commands 14 7 14 1 2 8 Insertion and Deletion
26. The same is not necessarily true for some of the other characters In some cases where no existing character is even close a space may be substituted for the missing character Clearly in some cases this will cause a loss of information content in the screen display Be sure to check a given terminal for its level of alternate character set support if you wish to use it with software that makes extensive use of the alternate character set At all times however the display of an alternate character set symbol will occupy one screen position even if all that is displayed is a space thus preserving the vertical alignment of screen displays regardless of the available alternate character set symbols AMOS Terminal System User s Guide 12 USING THE PRINTER PORT Some terminals contain the ability to be directly connected to a printer in addition to the host computer This method of connection is referred to as a printer port This printer port can be used for a variety of purposes The two primary uses are printing a copy of the current screen contents Print Screen and performing localized printing bypassing the terminal Transparent Print In situations where the terminal is connected to the host computer via a modem use of the printer port to connect a printer to the host may be far preferable to the cost of another set of modems and another phone line In addition to these two uses which are described in more detail l
27. Y 119 Y 120 Y 121 Y 122 Y 123 Y 124 Y 125 Y 126 Y 127 Y 128 Y 129 Y 130 Y 131 Y 132 Y amp OWSOrvii aw AMOS Terminal System User s Guide Code Summaries The codes shown below are embedded in the display text to achieve the indicated results Table B 2 Status Line Attribute Codes NOTE 1E hex turns off dim mode 1F hex turns on dim mode Attribute Code Control A Control C Control E Control G Control Control K Control M Control O Screen Attribute Effect Normal Blink Reverse Reverse and Blink Underscore Underscore and Blink Underscore and Reverse Underscore Reverse and Blink AMOS Terminal System User s Guide Page B 3 4 Code Summaries Table B 3 Color Selection Codes The codes shown below are used with the foreground color and background color selection commands Color Code Resulting Color Black White Blue Magenta Red Yellow Green Cyan NOOR WD O Only the first eight primary colors are shown here Additional values are variations on these colors following a scheme allowing automatic mapping to the nearest color Details on this scheme can be found in Chapter 8 and in the tables of Appendix C AMOS Terminal System User s Guide Code Summaries Page B 5 Table B 4 Alternate Character Set Commands Note These command are only valid after an Enter Alternate Character Set command TCRT
28. Zero One Two Three Four Five Six Seven Eight Nine Colon Semicolon Less Than Equal Sign Greater Than Question Mark Commercial At Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter AMOS Terminal System User s Guide ASCII Character Chart CHARACTER OCTAL 115 116 117 120 121 122 123 124 125 126 127 130 131 132 133 134 135 136 137 140 141 142 143 144 145 146 147 150 151 152 153 154 155 156 157 160 161 162 163 164 165 166 167 170 171 172 173 174 175 176 EL 177 ONXxz cadomovozxzx Qi77 7 N xXz c 0 7 00023 7 7 32o o 0ocoommm AMOS Terminal System User s Guide DECIMAL HEX 77 4 78 4 79 4 80 50 81 51 82 52 83 53 84 54 85 55 86 56 87 57 88 58 89 59 90 5A 91 5B 92 5C 93 5D 94 5E 95 5F 96 60 97 61 98 62 99 63 100 64 101 65 102 66 103 67 104 68 105 69 106 6A 107 6B 108 6C 109 6D 110 6E 111 eF 112 70 113 71 114 72 115 73 116 74 117 75 118 76 119 77 120 78 121 79 122 7 123 7 124 7 125 7D 126 7E 127 7 Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper Case Letter Upper
29. first position the cursor at the upper left corner of the area to be filled Issue a TCRT 1 91 call followed by height and width codes taken from Table B 5 Next output the single character you wish to have the area filled with The screen display will then be updated To fill an area of the screen with an attribute first position the cursor at the upper left corner of the area to be filled Issue a TCRT 1 90 call followed by height and width codes taken from Table B 5 Next output the attribute code taken from Table B 6 you wish to have the area filled with The screen display will then be updated All validation of the size of the block to be filled is left to the application program Using these commands with a block specified such that it will extend beyond the visible screen boundaries will have unpredictable results These functions are available only if the TD BLF bit is set in the terminal capabilities flags 13 28PLIT SCREENS To make it easier to maintain and update screen displays some terminals offer what is known as a split screen capability This capability allows you to divide the screen into two seperate and independent segments These two segments are completely independent of each other and behave as if they were actually seperate screens By this we mean that a clear screen command sent to one screen segment will only clear that segment leaving the other untouched Likewise scrolling text on the screen will only af
30. 39 TCRT 1 40 TCRT 1 41 TCRT 1 42 TCRT 1 43 TCRT 1 44 TCRT 1 45 TCRT 1 46 TCRT 1 47 TCRT 1 48 TCRT 1 49 TCRT 1 50 TCRT 1 51 TCRT 1 52 TCRT 1 53 TCRT 1 64 TCRT 1 65 TCRT 1 66 TCRT 1 67 TCRT 1 68 TCRT 1 69 TCRT 1 70 TCRT 1 71 TCRT 1 72 TCRT 1 73 TCRT 1 74 start graphics character mode end graphics character mode top left corner top right corner bottom left corner bottom right corner top intersect right intersect left intersect bottom intersect horizontal line vertical line intersection solid block slant block cross hatch block double line horizontal double line vertical up arrow down arrow raised dot end of line marker horizontal tab symbol paragraph dagger section cent sign one quarter one half AMOS Terminal System User s Guide AMOS Monitor TCRT Codes Page 14 7 TCRT 1 75 degree TCRT 1 76 trademark TCRT 1 77 copyright TCRT 1 78 registered 14 1 2 6Protected Field Commands TCRT 1 13 enable protected fields TCRT 1 14 disable protected fields 14 1 2 7Local Printer Commands TCRT 1 79 print screen TCRT 1 82 enter transparent print mode TCRT 1 83 exit transparent print mode TCRT 1 173 enter bidirectional print mode TCRT 1 174 exit bidirectional print mode 14 1 2 8Insertion and Deletion Commands TCRT 1 15 TCRT 1 16 TCRT 1 17 TCRT 1 18 TCRT 1 88 TCRT 1 89 TCRT 1 95 TCRT 1 96 TCRT 1 97
31. 5 15 effective USE 5 2 foreground 10 1 to 10 2 15 49 HLS system 5 16 to 5 18 Hue Lightness Saturation 5 16 e boe vent vetta pnt C 1 MIXTURES 5 aurei acea quts Fav are 5 13 NAMING ew UR RS 5 15 perceptual guidelines 5 11 physiological guidelines 5 10 physiology 5 2 reverse video 10 2 RGB system 5 15 SCISCUNG aie beds 10 1 AMOS Terminal System User s Guide AMOS Terminal System User s Guide selection software selection spectrum subtractive mixture usage guidelines worst combinations color deficient vision colorblindness column codes conversational mode cursor cursor address read read character cursor down cursor left cursor off cursor on cursor positioning cursor right cursor shape cursor up delete character delete column delete line design considerations hardware human software dim Double line box Drawing box drivers interface terminal edge discrimination erase to end of line erase to end of screen field terminals Form Feed character function keys translation tables graphics block box drawing line Greater than or Equal character hidden attributes HLS system AMOS Terminal System User s Guide Page Index 3 10 1 14 5 15 1 to 15 2 15 2
32. 61 TCRT 1 62 TCRT 1 63 TCRT 1 64 TCRT 1 65 TCRT 1 66 TCRT 1 67 TCRT 1 68 TCRT 1 69 TCRT 1 70 TCRT 1 71 TCRT 1 72 TCRT 1 73 TCRT 1 74 TCRT 1 75 TCRT 1 76 TCRT 1 77 TCRT 1 78 TCRT 1 79 TCRT 1 80 TCRT 1 81 TCRT 1 82 TCRT 1 83 AMOS Monitor TCRT Codes start underscore end underscore start reverse video end reverse video start reverse blink end reverse blink turn off screen display turn on screen display top left corner character top right corner character bottom left corner character bottom right corner character top intersect character right intersect character left intersect character bottom intersect character horizontal line character vertical line character intersection character solid block character slant block character cross hatch block character double line horizontal character double line vertical character send message to unshifted bottom status line send message to shifted bottom status line set normal display format set horizontal split follow with row code Set vertical split 39 char columns Set vertical split 40 char columns Set vertical split column to next char activate split segment 0 activate split segment 1 send message to top status line up arrow character down arrow character raised dot character end of line marker character horizontal tab character paragraph character dagger character section character cent sign
33. Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style On color terminals the reverse video attribute reverses the foreground and background colors For example if the currently selected colors are a white foreground on a blue background all reverse video text would be displayed as blue foreground characters on a white background This function is available only if the TD RVA bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 34END REVERSE VIDEO TEXT TCRT 1 33 This call disables the reverse video text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will
34. SOFTWARE The concept of device independence as applied to terminals is certainly not unique to Alpha Micro What is unique however is the depth to which this independence has been built into the System and the variety of different methods provided for achieving this independence The demands on this interface are quite extensive Typical of the types of items it must provide standardized access to are AMOS Terminal System User s Guide 1 4 Introduction eCursor positioning eClear screen einsert and delete lines characters and columns e Special effects like dim reverse video blinking or underlining ePutting text on one of the status lines eSelecting foreground and background colors eSelecting 80 or 132 column mode eAccepting input from function keys 1 4 1Dealing with the Compromises All of this cannot of course be achieved without some compromises Whenever a standard method of doing something must be set there will inevitably arise situations where the standard method is not the best method To help minimize these compromises the Alpha Micro terminal interface is considered to be an evolving standard That is the standard is intended to provide a best fit with the features found in the majority of the current terminals This means that over time the terminal interface standard changes usually in the area of assuming that additional features will be present However it is intended that these ch
35. Terminal System User s Guide 15 32 Terminal Control Commands 15 113START UNDERSCORED BLINKING TEXT W O A SPACE TCRT 1 112 This call enables the underscore and blinking text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 100 function but does not occupy a screen position This function is available only if the TD UND TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 114END UNDERSCORED BLINKING TEXT W O A SPACE TCRT 1 113 This call disables the underscore and blinking attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TC
36. This presents an obvious problem when you wish to use either type of attribute and be able to line up text on the screen To solve this problem the standard set of attribute commands implemented in the AMOS terminal system interface always occupies a screen position for all attribute changes This Screen position is taken regardless of whether the terminal hardware requires it even if it means that the terminal driver must output a dummy space By always assuming that a space will be present text can be assured of properly lining up on the screen regardless of the number of attribute changes that may or may not be present For those applications which require the use of hidden attributes such as underlining text in the middle of a word special terminal system calls are available to access attributes without spaces on those terminals which support the feature Because hidden attributes are not available on all terminals however use of them restricts your software to a smaller set of terminals 3 2 1 2Screen Flash An annoying problem with field attribute terminals is the phenomena known as screen flash This problem arises when an attribute momentarily occupies a large area of the Screen in the brief interval between issuing a begin attribute and an end attribute command To avoid this problem which is purely an aesthetic but very visible one the following procedure has been worked out This procedure works equally well with mo
37. White Green Red Yellow White Black Black Yellow White Cyan Green Black Blue Red Black Red Blue Blue White Yellow Cyan Yellow Magenta Black Cyan White Cyan Blue Black Red Red Blue Black Magenta Magenta Black White Blue Blue Black Yellow Yellow Red Blue Black Red Blue Black Figure 5 3 Best Color Combinations With Best First from G M Murch Physiological Principles for the Effective Use of Color AMOS Terminal System User s Guide 5 10 Using Color Effectively Background Thin Lines and Text Thick Lines and Panels White Yellow Cyan Yellow Cyan Black Blue Red Magenta Blue Magenta Red Magenta Blue Green Cyan Magenta Blue Green Cyan Green Cyan Magenta Yellow Cyan Magenta Yellow Blue Green Red Black Green Red Black Cyan Green Yellow White Yellow Green White Magenta Green Red Cyan Cyan Green Red Yellow White Cyan White Cyan Green Figure 5 4 Worst Color Combinations With Worst First from G M Murch Physiological Principles for the Effective Use of Color 5 4COGNITIVE PRINCIPLES The least understood area of effective color usage is how to capitalize on our modes of thinking about and associating with color This area of study falls into the realm of cognitive ergonomics Despite the infancy of this area of human factors study some initial observations prove useful in effective color usage An example involves the functional use of color st
38. a non distracting manner While primarily a menu driven product the experienced user is accommodated by a menu bypass option eliminating distracting information which a particular user may already have committed to memory All help information remains available at each screen in case a particular detail is forgotten eStatus information displayed during text editing is placed at the bottom of the screen in reduced intensity to reduce any distraction it might cause While these guidelines were specifically developed for AlphaWHRITE they have been successful enough to be used for later software development efforts such as AlphaCALC and AlphaMAIL The exact details of such guidelines are not nearly as important as the fact that you develop such guidelines to help you in screen design AMOS Terminal System User s Guide 5 USING COLOR EFFECTIVELY Color can add another important dimension to screen displays This chapter describes how we see colors and how that affects the way we should design our screens While this chapter presents a wide variety of information much of it seemingly unrelated to how to change colors on the screen it is intended to provide you with the information necessary to appreciate the complexities of color usage and to understand that color screen design is more than simply picking a pretty color Information on how to make your program select and control the screen colors can be found in Chapter
39. a permanent change in the data or System operation The desired direction is toward simplicity clarity and understandablity 4 4 1Human Characteristics Important to Screen Design A human being is a complex organism with a variety of attributes many of which are important to screen design Of particular importance are human perception memory and learning These areas unfortunately are not as clear cut as we would like We must turn to the science of cognitive psychology and human factors research to gain insight into these human characteristics Perception is our awareness and understanding of the elements of the environment through physical sensation This comprehension is achieved in light of our experience we classify stimuli based on models stored in our memories Perception tends to put things into wholes to establish order and meaning The human sensing mechanisms are constantly bombarded with a wide range of stimuli only some of which are important These important stimuli we can call signals the other stimuli noise It is our perception that allows us to separate the signals from the noise If however the noise level is too great our perception is overwhelm ed and we cannot determine what is important as a signal and what is meaningless The human perceptual mechanism seeks order and understanding when confronted with uncertainty Given a screen display humans will immediately try to make order out of the information groupi
40. agree on some characteristics of a good system Below is a list of some of these characteristics Adaptable system must be adaptable to the physical emotional intellectual and knowledge traits of the people whom it serves All office workers should be permitted to interact with a computer in a manner and style which best suits their needs In essence the system should be responsive to individual differences in interaction manner depth and style Transparent system must permit one s attention to be focused entirely on the task being performed without concern for the mechanics of the interface One s thoughts must be directed to the application not the communication Any operations which remind a worker of their presence are distracting Comprehendible A system should be understandable A person should know what to look at what to do when to do it why to do it and how to do it The flow of information commands responses and visual presentations should be in a sensible order that is easy to recollect and place in context Natural Operations should mimic the user s behavioral patterns Dialogs should mimic the office worker s thought processes and vocabulary Common human behavioral and perceptual traits should be taken into account in the design Predictable System actions should be expected within the context of other actions that are performed All expectations should be fulfilled uniformly and completely Responsive E
41. blink end underscore blink start underscore reverse end underscore reverse start underscore reverse blink end underscore reverse blink start underscore w o space end underscore w o space start reverse w o space end reverse w o space start reverse blinking w o space end reverse blinking w o space start underscore blinking w o space end underscore blinking w o space start underscore reverse w o space end underscore reverse w o space start underscore reverse blink w o space end underscore reverse blink w o space start blink w o space end blink w o space set cursor to blinking block set cursor to steady block set cursor to blinking underline Set cursor to steady underline RESERVED RESERVED RESERVED RESERVED select top status line w o address end status line select unshifted status line w o addr select shifted status line w o addr select black text obsolete select white text obsolete select blue text obsolete select magenta text obsolete select red text obsolete select yellow text obsolete 14 4 TCRT 1 138 TCRT 1 139 TCRT 1 140 TCRT 1 141 TCRT 1 142 TCRT 1 143 TCRT 1 144 TCRT 1 145 TCRT 1 146 TCRT 1 147 TCRT 1 148 TCRT 1 149 TCRT 1 150 TCRT 1 151 TCRT 1 152 TCRT 1 153 TCRT 1 154 TCRT 1 155 TCRT 1 156 TCRT 1 157 TCRT 1 158 TCRT 1 159 TCRT 1 160 TCRT 1 161 TCRT 1 162 TCRT 1 163 TCRT 1 164 TCRT 1 165 TCRT 1 166 TCRT 1 167 TCRT 1 168 TCR
42. character one quarter character one half character degree character trademark character copyright character registered character print screen set to 132 column mode set to 80 column mode enter transparent print mode exit transparent print mode AMOS Terminal System User s Guide AMOS Monitor TCRT Codes TCRT 1 84 TCRT 1 85 TCRT 1 86 TCRT 1 87 TCRT 1 88 TCRT 1 89 TCRT 1 90 TCRT 1 91 TCRT 1 92 TCRT 1 93 TCRT 1 94 TCRT 1 95 TCRT 1 96 TCRT 1 97 TCRT 1 98 TCRT 1 99 TCRT 1 100 TCRT 1 101 TCRT 1 102 TCRT 1 103 TCRT 1 104 TCRT 1 105 TCRT 1 106 TCRT 1 107 TCRT 1 108 TCRT 1 109 TCRT 1 110 TCRT 1 111 TCRT 1 112 TCRT 1 113 TCRT 1 114 TCRT 1 115 TCRT 1 116 TCRT 1 117 TCRT 1 118 TCRT 1 119 TCRT 1 120 TCRT 1 121 TCRT 1 122 TCRT 1 123 TCRT 1 124 TCRT 1 125 TCRT 1 126 TCRT 1 127 TCRT 1 128 TCRT 1 129 TCRT 1 130 TCRT 1 131 TCRT 1 132 TCRT 1 133 TCRT 1 134 TCRT 1 135 TCRT 1 136 TCRT 1 137 AMOS Terminal System User s Guide Page 14 3 begin writing to alternate page end writing to alternate page toggle page copy to alternate page insert column delete column block fill with attribute block fill with character draw a box scroll box up one line scroll box down one line select jump scroll select fast smooth scroll select med fast smooth scroll select med slow smooth scroll select slow smooth scroll start underscore
43. from lightness is often difficult since brighter colors invariably appear lighter as well And when dealing with a terminal screen which generates its own light separation becomes impossible 5 3 4Colors in Context Colors are also subject to contextual effects in which adjacent colors influence one another For example a color on a dark background appears lighter and brighter than the same color on a light background If a field is neutral gray or dark and displayed on a colored background the background induces color into the gray Red for example induces green into a neutral gray The size of a colored area also influences how we see it In general small areas become desaturated and can show a shift in hue This creates problems when text is color coded especially with blues and yellows because they are susceptible to small area color loss yellow text is often hard to distinguish from white text even though larger areas of the same colors are distinctly different Also small areas of color can mix red and green in smaller areas are eventually integrated by the visual system into yellow This is exactly the principle on which color video screens rely they depend on the merging of the many small dots of color into larger areas of single colors In other applications however the effect is not desirable AMOS Terminal System User s Guide Using Color Effectively Page 5 9 5 3 5Individual Characteristics So far perception h
44. increasingly insensitive to blues Similarly aging reduces the transmittance of the eye s fluids which makes colors appear less vivid and bright Actually age aside there is normally a great deal of variation with some people s eyes being very transparent and other s naturally yellowed This variation alone contributes to differences in color sensitivities among individuals 5 2 2The Retina The human retina consists of a dense collection of light sensitive rods and cones Rods are primarily responsible for night vision while cones provide the initial element in color sensation Photopigments in the cones translate wavelength to color sensation The range of sensation is determined by three photopigments blue 445 nanometers or nm green 535 nm and red 575 nm Red is really a misnomer because maximum sensitivity at 575 nm actually invokes the sensation of yellow not red Both photopigment and cone distribution vary over the retinal surface Red pigment is found in 64 of the cones green in 32 and blue in just 2 Additionally the center of the retina which provides detailed vision is densely packed with cones but has no rods Moving outward the number of rods increases to eventually outnumber the cones As a result shapes appear unclear and colorless at the periphery of vision Because of the cone and photopigment distributions we can detect yellows and blues farther into our peripheral vision than reds and greens Also
45. is left over which evokes the sensation of green This type of color mixture is called subtractive color mixture as bands of wavelengths are subtracted or cancelled by the combination of light absorbing materials If we add a third pigment to the mixture of yellow and cyan one that absorbs the middle band of wavelengths such as magenta or violet the surface would appear black since all of the light falling on it would be absorbed By this process of eliminating parts of the reflectance distribution through varying the amount of each pigment intermediate hues can be created In the example given above the resulting green would not be very light as much of the illumination falling on the surface is absorbed The mixture of two pigments produces a reflectance surface which absorbs more light than either pigment alone With a palette of only two pigments each with fairly broad reflectance distributions consisting of a red and a blue we can create all the intermediate hues by varying the density of each pigment The problem however is that the resulting hues will not be very light Adding a third fourth or fifth pigment to the palette helps a great deal by increasing the overlap in the reflectance distributions of each so that lighter mixtures can be produced In fact the minimal number of colors is three which are often referred to as the primary colors of subtractive color mixture An artist of course uses many other colors in order to i
46. itself but brightness depends on the amount of light illuminating the object A good illustration of all of this is black print on white paper Changing illumination has little perceptual effect on the relative lightness of the paper or print since the ratio of reflectance or contrast remains unchanged Even in dim light the white paper stays white and the black ink stays black 5 3 3Perception of Chromatic Color Objects that reflect or emit unequal distributions of wavelengths are said to be chromatic i e to have a color The color we sense derives from the physical attributes of the dominant wavelengths the intensity of the wavelengths and the number and proportion of reflected wavelengths Color identification also depends upon a multitude of learned variables such as previous experiences with the object and association of specific sensations with color names The sensation is also affected by the context in which the color occurs and the characteristics of the surrounding area or the colors of other objects Because color perception is subjective many of its aspects can be described only in the psychological dimensions of lightness saturation hue and brightness rather than in any absolute physical terms Hue is the sensation reported by observers exposed to wavelengths between approximately 380 and 700 nm the range of light that the human eye is sensitive to For the range between 450 and 480 nm the predominant sensation report
47. level can also be used to connote the strength of relationships Link the degree of color change to event magnitude As an alternative to bar charts or tic marks on amplitude scales one can portray magnitude changes with progressive steps of changing color A desaturated cyan can be increased in saturation as the graphed elements increase in value Progressively switching from one hue to another can be used to indicate passing critical levels Order colors by their spectral position To increase the number of colors on a display requires imposing a meaningful order on the colors The most obvious order is that provided by the spectrum with the mnemonic ROY G BIV red orange yellow green blue indigo violet Warm and cool colors should indicate action levels Traditionally the warm long wavelength colors are used to signify action or the requirement of a response Cool colors on the other hand indicate status or background information Most people also experience warm colors advancing toward them thereby forcing attention and cool colors receding or drawing away This is apparently caused by the focus shift required by the different colors and the everyday experience of atmospheric absorption where more distant object appear bluer than nearby objects AMOS Terminal System User s Guide 5 14 Using Color Effectively 5 6COLOR MIXTURE Having decided what colors we want on our displays and hardcopy it becomes useful t
48. of over 16 million different colors 5 7DESCRIBING COLORS One of the problems we must face when using colors with a computer is the task of being able to describe and name colors While most of us could agree on a color we could all describe as blue we are less likely to agree on what exactly is meant by light blue sky blue baby blue or any of several hundred other slight variations on the same theme As we have seen this results not only from personal opinion and experience but also from actual differences in the way different people experience color When we are dealing among ourselves this does not present a major problem as it is possible to add additional adjectives to our description to reach agreement or if all else fails to compare color chips to reach a consensus This is not possible however when it comes to a program trying to specify a color to a display Even if it were possible for the program to show a color chip to the display and ask for a color just like it it is not likely that the display would respond in any meaningful fashion Because the same problem has been faced by color television engineers and artists and printers before them a number of systems for describing colors in a mathematical fashion have been devised Most of these while fairly accurate in terms of color specification and repeatability are difficult to use and do not correspond to our intuitive sense of color The system most familiar
49. offsets are from the base of the file not including any file system links Bytes 0 3 Four bytes of zero Bytes 4 515 A table of 256 word offsets This table is indexed by the function key code in the range 0 255 and yields an offset from the base of the file to the characters the function key is to be translated to Bytes 516 nnnnn A series of null terminated strings which are pointed to by the offset table The sequence of events used to translate a function key is as follows 1 Take the function key code to be translated and multiply it by two 2Add four to the result 3Use the result as an index into the translation file to retrieve an offset word 4Use this offset word as an index into the translation file This index will point to the characters to be substituted for the function key Note that a function key can have no translation at all if the byte it indexes is zero a single character substitution or an arbitrarily long substitution Any character can be translated via a function key translation table not just those commonly referred to as function keys AMOS Terminal System User s Guide Page D 2 Function Key Translation Tables D 2SET PFK STYLE TRANSLATION TABLES A somewhat different style of function key translation table is used to implement the SET PFK function of AMOS Because these translation tables are loaded into memory at all times the format of the table has been optimized to reduce memory requirements a
50. placed That way when the software is used on terminals which possess only the single bottom status line the most important information will still be available Certain system software uses the top status line to display system status information and to notify you of system events such as incoming mail For this reason only non vital information should be placed on the top status line as the system may remove it from the Screen 8 4STATUS LINE EMULATION While most terminals have a bottom status line not all of them have an addressable status line Some terminal drivers however have been written to emulate an addressable status line This emulation should be transparent to your software although some performance degradation may be apparent to the user If this type of performance is critical to your application you should avoid the use of terminal drivers which emulate status lines AMOS Terminal System User s Guide CHAPTER 9 USING PROGRAMMED FUNCTION KEYS While most of the work that the terminal service system must do to achieve terminal independence is on the output side converting standard calls to the unique output required by a given terminal the input side is also important The use of function keys has become quite popular in software packages due to their inherent ease of use As with everything else having to do with terminals however there is a multitude of different methods used for implementing them To allow software
51. properly line up irrespective of the terminal attribute style This function is available only if the TD RVA bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 35START REVERSE VIDEO BLINKING TEXT TCRT 1 34 This call enables both the reverse video and the blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style On color terminals the reverse video attribute reverses the foreground and background colors AMOS Terminal System User s Guide 15 10 Terminal Control Commands For example if the currently selected colors are a white foreground on a blue background all reverse video text would be displayed as blue foregr
52. satisfactory An example of such a situation is where a given application program relies on drawing boxes to segment different types of data A terminal which does not support the box drawing TCRT calls would most likely just cause the application program to draw the boxes with the alternate character set making the application fully functional albeit with slightly reduced display speed A terminal with neither box drawing commands or an alternate character set would cause more AMOS Terminal System User s Guide Assembly Language Terminal Drivers Page 16 9 difficulty In this case there is no good way for the applications program to separate the different data elements In such a situation it makes more sense for the terminal driver to offer a solution rather than placing an additional burden on the application program In this case the problem is easily solved by substituting appropriate characters from the normal character set for the missing alternate character set While using dashes and pluses instead of line drawing symbols may not be as attractive the application program can be used without confusion This technique of substituting normal characters for missing alternate characters is one of several different techniques that can be used to emulate missing terminal features within a terminal driver Other possible techniques include eSubstituting one feature for another eEmulation by combining features Full emulation of non e
53. screen area TCRT 1 150 enter full graphics mode TCRT 1 151 exit full graphics mode TCRT 1 155 enable proportionally spaced text TCRT 1 156 disable proportionally spaced text TCRT 1 158 enable graphics cursor TCRT 1 159 disable graphics cursor TCRT 1 160 select graphics cursor shape TCRT 1 161 select graphics cursor location TCRT 1 162 select graphics cursor regions TCRT 1 176 Set terminal date TCRT 1 178 select PC character set TCRT 1 179 select PC default character set TCRT 1 180 select PC terminal emulation TCRT 1 181 select ASCII terminal operation TCRT 1 182 select AUX port host TCRT 1 183 select main port host TCRT 1 184 select toggle host ports TCRT 1 185 select 8 bit character display TCRT 1 186 select 7 bit character display TCRT 1 187 select 8 bit keyboard mode TCRT 1 188 select 7 bit keyboard mode TCRT 1 189 select primary printer port TCRT 1 190 select secondary printer port TCRT 1 191 select 161 column display mode 14 2RESERVED CODES In the interest of maximizing the compatibility between software packages developed to run on the Alpha Micro computer and to minimize unwanted interactions between such packages all unassigned TCRT codes are reserved for assignment by Alpha Micro If you have a special application or terminal which requires additional TCRT codes please contact Alpha Microsystems to request having a TCRT code assigned AMOS Terminal System User s Guide
54. space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 68END OF LINE CHARACTER TCRT 1 67 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a tilde character is normally substitu ted AMOS Terminal System User s Guide Terminal Control Commands Page 15 19 15 69HORIZONTAL TAB CHARACTER TCRT 1 68 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a vertical bar character is norm
55. terminal status word and the actual translation in an assembly language subroutine AMOS Terminal System User s Guide 10 PROGRAMMING COLOR TERMINALS 10 1THE IMPACT OF COLOR Color can add an important new dimension to your screen displays In Chapter 5 we discussed how color is perceived and important aspects of its usage This chapter describes how color control has been implemented in the AMOS terminal system and how you may use it in your programs 10 2SELECTING COLORS WITH SOFTWARE Two different methods of selecting color on the screen are available The first which makes use of the terminal commands TCRT 1 132 through 1 147 is intended for use on the AM 70 and similar terminals only and is considered to be obsolete for the purposes of developing new software It is restricted to dealing with the eight additive primary colors as well as behaving as a field attribute occupying a screen position and severely restricting how it can be used in formatted screen displays The second and much more flexible method of designating color makes use of the commands TCRT 2 n and TCRT 3 n This method allows independent selection of foreground and background and provides for as many as 256 different foreground and background colors to be displayed on the screen at the same time The use of these commands is recommended for all new software development 10 3USING FOREGROUND AND BACKGROUND COLOR SELECTION The preferre
56. the screen by block filling with space or to establish a background texture by block filling with some other character To fill an area of the screen first position the cursor at the upper left corner of the area to be filled Issue a TCRT 1 91 call followed by height and width codes taken from Table B 5 defining the lower right corner of the area Next output the single character you wish to have the area filled with The screen display will then be updated All validation of the size of the block to be filled is left to the application program Using this command with a block specified such that it will extend beyond the visible screen boundaries will have unpredictable results This function is available only if the TD BLF bit is set in the terminal capabilities flags 15 93DRAW A BOX TCRT 1 92 This command allows you to draw a box on the screen This box encloses a rectangular area of the screen with line drawing graphics characters Note that only the outside lines of the box are drawn on the screen characters inside and outside the box are unaffected by this command If you wish to clear the inside of the box the use of the Block Fill with Character command TCRT 1 91 is recommended To draw a box first position the cursor at the upper left corner of the box Issue a TCRT 1 92 call followed by height and width codes taken from Table B 5 which define the lower right corner of the area The screen display will then be
57. the screen with spaces This accomplishes the same function but is considerably slower 15 12START REDUCED INTENSITY TCRT 1 11 All text written after issuing this command up to the use of a TCRT 1 12 call below is displayed in reduced intensity On terminals which support protected fields this text will also be protected from erasure if a TCRT 1 13 call has been issued prior to this command Issuing this call does not alter the cursor position or occupy a screen position This function is available only if the TD DIM bit is set in the terminal capabilities flags 15 13END REDUCED INTENSITY TCRT 1 12 All text written after issuing this command is displayed in normal intensity This command is used to reverse the effects of the TCRT 1 11 call discussed above On terminals which support protected fields this text will be subject to erasure even if a TCRT 1 13 call has been issued Issuing this call does not alter the cursor position or occupy a screen position This function is available only if the TD DIM bit is set in the terminal capabilities flags AMOS Terminal System User s Guide 15 4 Terminal Control Commands 15 14ENABLE PROTECTED FIELDS TCRT 1 13 This call enables protected fields Any text subsequently written on the screen in dim mode is protected from erasure Detailed information on the operation of protected fields may be found in Chapter 7 of this manual Protected fields may b
58. the terminal capabilities flags 15 63ACTIVATE SCREEN SEGMENT 1 TCRT 1 62 This command selects screen segment 1 the lower part for horizontal split the right part for vertical split as the place to receive all subsequent commands and text Segment 1 will remain the active segment until an Activate Screen Segment 0 command TCRT 1 61 command is given or the screen is unsplit via a TCRT 1 56 command This command is only valid after a split screen command TCRT 1 57 1 58 or 1 59 has been given It is ignored if the terminal screen is not currently split This function is available only if the TD SPL bit is set in the terminal capabilities flags 15 64SELECT TOP STATUS LINE TCRT 1 63 This command selects the top status line as the place to receive subsequent text After issuing this TCRT call you must send a column position where you wish the text to begin This column position can be selected from Table B 1 After sending the column position the text to be displayed on the status line should then be sent Details on the use of status lines can be found in Chapter 8 After issuing this command sending the column address and the desired text you must terminate the command by using the End Status Line functions TCRT 1 129 This function is available only if the TD STS bit is set in the terminal capabilities flags AMOS Terminal System User s Guide 15 18 Terminal Control Commands 15 65UP ARR
59. then clear and will be split The upper segment segment 0 is automatically selected The cursor will appear only in the active segment However whenever a segment is selected the cursor will return to the position within the segment where it was last located AMOS Terminal System User s Guide 15 16 Terminal Control Commands The screen will stay split until a TCRT 1 56 is issued This function is available only if the TD SPL bit is set in the terminal capabilities flags 15 59SET VERTICAL SCREEN SPLIT W 39 CHARACTERS TCRT 1 58 This command allows you to divide the screen into two independent areas Each of these areas can be separately addressed cleared and otherwise worked with just as it were an entire screen You select which of these segments you wish to work with by using the TCRT 1 61 and 1 62 commands to select the active segment The active segment behaves just a a normal screen but does so without disturbing the other segment This command splits the screen into two vertical halves of 39 characters each The 40th character position in each half is reserved for a dividing line set via the TCRT 1 60 command The cursor will appear only in the active segment However whenever a segment is selected the cursor will return to the position within the segment where it was last located The screen will stay split until a TCRT 1 56 is issued This function is available only if the TD SPL bit is set
60. user 4 2THE REAL WORLD Of course there is probably no system in existence that has all of these attributes In addition many of the features listed above can only be the result of good system level design well beyond our ability to influence with simple screen design But yet with most systems the terminal screen is just about all of the system that anyone ever sees As the only visible part of a computer system it need to be beyond reproach By giving the user a good first impression a good screen design can actually help overcome deficiencies is other parts of the system As with everything else in the world great screen design is both hard to create and rare However there are so many truly awful screen designs in the world that to create a good screen design is not that hard Simply by observing a few guidelines and thinking carefully about how the screen will be viewed and used we can make screens that make the computer system easier to use more productive easier to sell and a pleasure to use Better still the principles of good screen design can be applied to existing applications improving existing systems with only a small amount of effort 4 3THE WELL DESIGNED SCREEN Two types of considerations drive the design of a good screen display Human considerations are the needs and requirements of people and are oriented toward clarity meaningfulness and ease of use Hardware and software considerations reflect the physical const
61. we have defined a simple eight bit subset of the HLS color space which conveniently allows a set of up to 256 colors to be displayed By carefully choosing how this set is mapped it has been possible to set it up such that colors will automatically map to the closest color to the one specified when the display device is not capable of displaying the full 256 color range For example a program which specifies a color assuming that the full 256 color range is available will still work on a terminal which displays only 8 colors Because of the way in which the colors are mapped the nearest available color will be chosen automatically The Alpha Micro color map defines these 256 colors in terms of their HLS coordinates a descriptive color definition and their RGB values This allows programs complete freedom in converting from one color space to another Appendix C lists the Alpha Micro color map in detail as well as giving the equivalent color description HLS coordinates and RGB values Chapter 10 describes how to use the color selection commands to display colors on your display AMOS Terminal System User s Guide Using Color Effectively Page 5 19 Sorry but this image could not be converted to Adobe Acrobat Format Please refer to your printed manual for this picture Figure 5 5 The HLS Color Description Model AMOS Terminal System User s Guide PART TERMINAL FEATURE OVERVIEW AMOS Terminal System User s Guide
62. your printed manual for this picture AMOS Terminal System User s Guide Using Color Effectively Page 5 3 Figure 5 1 Gross Structure of the Human Eye AMOS Terminal System User s Guide 5 4 Using Color Effectively 5 2 1The Lens Camera lens designers go to great lengths to color correct the lenses they design so that all colors are evenly focused on the film yielding a sharp color photo Unlike the lens in your camera the lens of the human eye is not color corrected Different colors of light are focused at different points within your eye causing chromostereopsis an effect that causes two pure colors at the same distance from the eye to appear to be at two different distances For most people reds appear closer and blues more distant In fact short wavelengths pure blue always focus in front of the retina and thus appear defocused This is most noticeable at night when deep blue signs seem fuzzy and out of focus while other colors appear sharp Lens transmissivity also has an effect on how we perceive color While it may appear to be clear the lens absorbs almost twice as much energy in the blue region as in the yellow or red region Also a pigment in the retina s center transmits yellow while absorbing blue The net result is a relative insensitivity to shorter wavelengths cyan to deep blue and enhanced sensitivity to longer wavelengths yellows and oranges As we grow older lens yellowing increases making us
63. 34 select blue text on black background 1 135 select magenta text on black background 1 136 select red text on black background 1 137 select yellow text on black background 1 138 select green text on black background 1 139 select cyan text on black background AMOS Terminal System User s Guide 10 4 Programming Color Terminals The TCRT calls 1 140 through 1 147 are used to select black text on different colored backgrounds The calls are assigned as follows 1 140 1 141 1 142 1 143 1 144 1 145 1 146 1 147 select black text on black background select black text on white background select black text on blue background select black text on magenta background select black text on red background select black text on yellow background select black text on green background select black text on cyan background These calls are considered to be obsolete and are provided primarily to support older applications with limited color selection capability Because the presence of colors removes the availability of some of the standardly available attributes most notably the blinking and underline attributes some application systems assign the TCRT calls which generate those attributes to color selection instead This technique makes sure that programs which try to use the missing attributes still have some distinguishing attribute on the screen but reliance on this technique for color selection will cause th
64. 52 0 67 0 00 0 33 53 0 67 1 00 0 33 54 0 00 0 67 0 33 55 0 33 1 00 0 67 56 0 67 0 67 0 33 57 1 00 1 00 0 67 58 0 00 0 33 0 67 59 1 00 0 33 0 67 60 0 67 0 33 0 00 61 1 00 0 67 0 33 62 0 33 0 67 0 00 63 0 33 0 67 1 00 AMOS Terminal System User s Guide H L S Description 300 0 667 0 500 Light cyan 1 60 0 500 0 334 Purple gray 60 0 834 0 200 Light magenta 30 0 334 1 000 Indigo 30 0 667 0 500 Light purple gray 90 0 334 1 000 Burgundy 210 0 667 0 500 Gray green 270 0 334 1 000 Faded blue green 270 0 667 0 500 Pale cyan 180 0 500 0 334 Tan 180 0 834 0 200 Cream 330 0 334 1 000 Dull blue 90 0 667 0 500 Purple pink 150 0 334 1 000 Orange brown 150 0 667 0 500 Light brown 210 0 334 1 000 Khaki green 330 0 667 0 500 Light blue 1 APPENDIX D FUNCTION KEY TRANSLATION TABLES AMOS provides support for programmed function keys in a very generalized fashion imposing no fixed structure or method of implementation onto the programmer you are free to map a function key into its result in any fashion you wish However AMOS does implement two different standardized methods of performing function key translation This appendix describes the format of the internal tables used by these two methods D 1STANDARD FUNCTION KEY TRANSLATION TABLES This section describes the internal format of the function key translation tables created by the FIXTRN program and used by such application programs as AlphaVUE AlphaWRITE AlphaCALC and MULTI All
65. 8 2 62 106 Y 19 3 63 107 Y 20 4 64 108 Y 21 5 65 a 109 Y 22 6 66 b 110 Y 23 7 67 C 111 Y 0 24 8 68 d 112 Y 1 25 9 69 e 113 Y 2 26 70 f 114 Y 27 71 9 115 Y 4 28 lt 72 116 5 29 73 117 Y 6 30 gt 74 j 118 Y 7 31 75 k 119 Y 8 32 76 120 Y 9 33 A 77 m 121 Y 34 B 78 n 122 Y 35 C 79 o 123 Y lt 36 D 80 p 124 Y 37 E 81 q 125 Y gt 38 F 82 r 126 Y 39 G 83 S 127 Y 40 H 84 t 128 Y A 41 85 129 Y B 42 J 86 130 Y 43 K 87 131 Y 44 L 88 X 132 Y E AMOS Terminal System User s Guide Code Summaries Page B 7 Table B 6 Fill Area Attribute Codes The codes shown below are used with the Fill Area with Attributes command to set the appropriate attribute Attribute Code Screen Attribute Effect 0 1 Blank no display 2 Blink 4 Reverse 6 Reverse and blink 8 Underscore Underscore and blink Underscore and reverse gt Underscore reverse and blink p Dim r Dim and blink t Dim and reverse V Dim reverse and blink X Dim and underscore 2 Dim underscore and blink Dim underscore and reverse Dim underscore reverse and blink AMOS Terminal System User s Guide APPENDIX C THE ALPHA MICRO COLOR MAP This appendix lists the first 64 colors contained in the Alpha Micro color map along with the RGB and HLS representations of those colors The RGB value is given as the relative value assigned to each of the t
66. Case Letter Upper Case Letter Upper Case Letter Opening Bracket Back Slash Closing Bracket Circumflex Underline Grave Accent Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Lower Case Letter Opening Brace Vertical Line Closing Brace Tilde Delete Page A 3 APPENDIX B CODE SUMMARIES This appendix contains various tables and charts summarizing the various code sequences required by some terminal commands AMOS Terminal System User s Guide 2 Row number rorc 1 2 3 4 5 6 7 8 ASCII Character space amp OONDOORWN O ACT ITOMMINODFOvii as Row and Column Codes Table B 1 c Column number rorc ASCII Character gt N xz cdomxovozzr Z c70 0002437 7 5 7v7207 0o0ooonmn rorc ASCII Character c NE 95 96 DEL Code Summaries 97 Y space 98 Y 99 Y 100 Y 101 Y 102 Y 103 Y 104 Y 105 Y 106 Y 107 Y 108 Y 109 Y 110 Y 111 Y 112 Y 113 Y 114 Y 115 Y 116 Y 117 Y 118
67. D bit is set in the terminal capabilities flags AMOS Terminal System User s Guide 15 24 Terminal Control Commands 15 91BLOCK FILL WITH ATTRIBUTE TCRT 1 90 This command allows you to fill a rectangular area of the screen with a specific attribute This is useful for establishing a particular attribute for a section of the screen To fill an area of the screen first position the cursor at the upper left corner of the area to be filled Issue a TCRT 1 90 call followed by height and width codes taken from Table B 5 defining the lower right corner of the area Next output the coded character corresponding to the attribute you wish to fill with The screen display will then be updated All validation of the size of the block to be filled is left to the application program Using this command with a block specified such that it will extend beyond the visible screen boundaries will have unpredictable results This function is available only if the TD BLF bit is set in the terminal capabilities flags Because this command depends both on the availability of block fill commands in the terminal and on the terminal being a field oriented terminal care should be taken in its use to avoid restricting the use of the software to a small number of terminals 15 92BLOCK FILL WITH CHARACTER TCRT 1 91 This command allows you to fill a rectangular area of the screen with a specific character This is useful for clearing an area of
68. EXT TCRT 1 144 This command selects the current text color to be the background color on a red background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags AMOS Terminal System User s Guide 15 40 Terminal Control Commands 15 143SELECT YELLOW REVERSE TEXT TCRT 1 145 This command selects the current text color to be the background color on a yellow background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 144SELECT GREEN REVERSE TEXT TCRT 1 146 This command selects the current text color to be the background color on a green background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals suc
69. If a particular terminal does not have this function this call will simply be ignored AMOS Terminal System User s Guide Terminal Control Commands Page 15 3 15 9UNLOCK KEYBOARD TCRT 1 8 This call enables the keyboard allowing the operator to send input to the computer This call reverses the effect of TCRT 1 7 described above If a particular terminal does not have this function this call will simply be ignored 15 10ERASE TO END OF LINE TCRT 1 9 This call causes the text to the right of the cursor to be cleared from the display The text is cleared from the current cursor position including the character the cursor is positioned on to the end of the current screen line This function is available only if the TD EOL bit is set in the terminal capabilities flags Some terminal drivers may simulate this function by overwriting the remainder of the line with spaces and repositioning the cursor This accomplishes the same function but is considerably slower 15 11ERASE TO END OF SCREEN TCRT 1 10 This call causes the text to the right of the cursor and on all following lines to be cleared from the display The text is cleared from the current cursor position including the character the cursor is positioned on to the last row in the current screen segment This function is available only if the TD EOS bit is set in the terminal capabilities flags Some terminal drivers may simulate this function by overwriting the remainder of
70. O A SPACE TCRT 1 106 This call enables the underscore text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 30 function but does not occupy a screen position This function is available only if the TD UND and TD NSP bits are set in the terminal capabilities flags AMOS Terminal System User s Guide 15 30 Terminal Control Commands Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 108END UNDERSCORED TEXT W O A SPACE TCRT 1 107 This call disables the underscore text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 31 command but does not occupy a screen position This function is avai
71. OW CHARACTER TCRT 1 64 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 66DOWN ARROW CHARACTER TCRT 1 65 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 67RAISED DOT CHARACTER TCRT 1 66 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a
72. RINT SCREEN TCRT 1 79 This call causes the contents of the current screen display to be sent to the local printer port if the terminal is so equipped Note that the exact results of this operation will depend not only on the terminal being used but also the printer that is attached to it This is especially true in the area of characters in the alternate character set that may be displayed on the terminal screen as not all printers have the capability of printing these characters This function is available only if the TD PRT bit is set in the terminal capabilities flags 15 81SET TO 132 COLUMN MODE TCRT 1 80 This call selects the 132 column display mode on the terminal If the terminal is already in 132 column mode no operation is performed AMOS Terminal System User s Guide 15 22 Terminal Control Commands Programs using this call must assume that the screen display is cleared when this call is issued even though not all terminals will clear the screen To reduce the possiblity of an improper Screen display appearing the entire screen should be cleared prior to issuing this call In addition to changing the screen format this call also changes the value which will be returned for number of columns when a TRMCHR call is issued This function is available only if the TD 132 bit is set in the terminal capabilities flags 15 82SET TO 80 COLUMN MODE TCRT 1 81 This call selects the 80 column display mode on the termina
73. RT 1 101 command but does not occupy a screen position This function is available only if the TD UND TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 115START UNDERSCORED REVERSE VIDEO TEXT W O A SPACE TCRT 1 114 This call enables the underscore text and reverse video attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 102 function but does not occupy a screen position This function is available only if the TD RVA and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space sho
74. System User s Guide Protected Fields Page 7 3 7 Position the cursor and accept input or output any characters you do not wish to have protected This is the state that the program will be in for the majority of the time As each query is responded to the cursor position is updated and the next input is expected 8When a complete screenful of information has been accepted and a new empty Screen is desired position the cursor as necessary and issue the appropriate erase command to clear out all characters except the protected text 9When the program is ready to erase the protected character such as when it must display a different form turn off protected fields via a TCRT 1 14 command and erase the text via any one of the erase commands Because you cannot predict how any given terminal will deal with interaction between the cursor and protected fields the applications software must perform all cursor movements between fields not rely on the terminal to skip the cursor over any protected text For example some terminals will not allow the cursor to be positioned within protected text and will force the cursor to be positioned on the next unprotected region of the screen while others will allow the cursor to be placed anywhere but will not allow any write of characters to that screen location Still others regard the protected fields as only protected against erasure and do no checking whatsoever when positioning the cursor or w
75. T 1 169 TCRT 1 170 TCRT 1 171 TCRT 1 172 TCRT 1 173 TCRT 1 174 TCRT 1 175 TCRT 1 176 TCRT 1 177 TCRT 1 178 TCRT 1 179 TCRT 1 180 TCRT 1 181 TCRT 1 182 TCRT 1 183 TCRT 1 184 TCRT 1 185 TCRT 1 186 TCRT 1 187 TCRT 1 188 TCRT 1 189 TCRT 1 190 TCRT 1 191 AMOS Monitor TCRT Codes select green text obsolete select cyan text obsolete select black reverse text obsolete select white reverse text obsolete select blue reverse text obsolete select magenta reverse text obsolete select red reverse text obsolete select yellow reverse text obsolete select green reverse text obsolete select cyan reverse text obsolete save a rectangular area restore a rectangular screen area enter full graphics mode exit full graphics mode draw a box with rounded corners draw a window style box draw a box with double lines enable proportionally spaced text disable proportionally spaced text select color palette by RGB value enable graphics cursor disable graphics cursor select graphics cursor shape include graphics cursor location define graphics cursor regions output form feed character output line feed character output new line character output vertical tab character output plus or minus character output greater than or equal character output less than or equal character output not equal character output British pound character output Pi character enter bidirectional print mode exit bidi
76. TCRT 1 98 TCRT 1 99 14 1 2 10Split Screen Commands TCRT 1 56 TCRT 1 57 TCRT 1 58 TCRT 1 59 TCRT 1 60 TCRT 1 61 TCRT 1 62 AMOS Terminal System User s Guide delete line insert line delete character insert character insert column delete column 14 1 2 9Variable Speed Scroll Commands select jump scroll select fast smooth scroll select med fast smooth scroll select med slow smooth scroll select slow smooth scroll set normal display format set horizontal split follow with row code Set vertical split 39 char columns Set vertical split 40 char columns set vertical split column to next char activate split segment 0 activate split segment 1 14 8 14 1 2 11Block Fill Commands TCRT 1 90 TCRT 1 91 14 1 2 12Box Commands TCRT 1 92 TCRT 1 93 TCRT 1 94 TCRT 1 152 TCRT 1 153 TCRT 1 154 14 1 2 13Alternate Page Commands TCRT 1 84 TCRT 1 85 TCRT 1 86 TCRT 1 87 14 1 2 14Color Commands TCRT 2 n TCRT 3 n TCRT 1 132 TCRT 1 133 TCRT 1 134 TCRT 1 135 TCRT 1 136 TCRT 1 137 TCRT 1 138 TCRT 1 139 TCRT 1 140 TCRT 1 141 TCRT 1 142 TCRT 1 143 TCRT 1 144 TCRT 1 145 TCRT 1 146 TCRT 1 147 TCRT 1 157 TCRT 1 177 AMOS Monitor TCRT Codes block fill with attribute block fill with character draw a box scroll box up one line scroll box down one line draw a box with rounded corner draw a window style box draw a box with dou
77. TCRT Codes by Number TCRT 1 0 clear screen TCRT 1 1 cursor home move to column 1 1 TCRT 1 2 cursor return move to column 1 TCRT 1 3 cursor up TCRT 1 4 cursor down TCRT 1 5 cursor left TCRT 1 6 cursor right TCRT 1 7 lock keyboard TCRT 1 8 unlock keyboard TCRT 1 9 erase to end of line TCRT 1 10 erase to end of screen TCRT 1 11 reduced intensity TCRT 1 12 normal intensity TCRT 1 13 enable protected fields TCRT 1 14 disable protected fields TCRT 1 15 delete line TCRT 1 16 insert line TCRT 1 17 delete character TCRT 1 18 insert character TCRT 1 19 read cursor address TCRT 1 20 read character at current cursor position TCRT 1 21 start blink field TCRT 1 22 end blink field TCRT 1 23 start graphics character mode TCRT 1 24 end graphics character mode TCRT 1 25 Set horizontal position obsolete TCRT 1 26 Set vertical position obsolete TCRT 1 27 set terminal attributes TCRT 1 28 cursor on TCRT 1 29 cursor off AMOS Terminal System User s Guide 14 2 TCRT 1 30 TCRT 1 31 TCRT 1 32 TCRT 1 33 TCRT 1 34 TCRT 1 35 TCRT 1 36 TCRT 1 37 TCRT 1 38 TCRT 1 39 TCRT 1 40 TCRT 1 41 TCRT 1 42 TCRT 1 43 TCRT 1 44 TCRT 1 45 TCRT 1 46 TCRT 1 47 TCRT 1 48 TCRT 1 49 TCRT 1 50 TCRT 1 51 TCRT 1 52 TCRT 1 53 TCRT 1 54 TCRT 1 55 TCRT 1 56 TCRT 1 57 TCRT 1 58 TCRT 1 59 TCRT 1 60 TCRT 1
78. This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 48VERTICAL LINE CHARACTER TCRT 1 47 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 49CENTER INTERSECTION CHARACTER TCRT 1 48 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a spac
79. URSOR TO STEADY UNDERLINE TCRT 1 123 This command sets the text cursor shape to be that of a steady non blinking underline On terminals which do not support changing the cursor shape this command will be ignored 15 125RESERVED FUNCTIONS TCRT 1 124 THROUGH TCRT 1 127 These functions are reserved for future expansion by Alpha Micro If you have a specific need for a new TCRT function you may contact Alpha Micro to reserve a TCRT call number The reservation process avoids problems arising from incompatible extensions to the TCRT functions 15 126SELECT TOP STATUS LINE W O ADDRESS TCRT 1 128 This function allows you to send text to the top status line Immediately after issuing this command send the text you wish displayed on the status line followed by an End Status Line TCRT 1 129 command Details on the use of status lines can be found in Chapter 8 This command is similar to the TCRT 1 63 command but only allows writing to the entire status line without individually addressable columns This makes this command less efficient than the TCRT 1 63 command but is supported by a wider variety of terminals The size of the status line referenced by this command may be found via the TRMCHR monitor call On terminals with only a single status line this function will address that status line This function is available only if the TD STS bit is set in the terminal capabilities flags AMOS Terminal System User s Guide
80. USING STATUS LINES Before using any status line the very first thing that must be done is to check the TD STS flag in the capabilities word returned by TRMCHR If this bit is not set no status line support is provided by the terminal in question and no further status line operations should be performed 8 2 1Displaying Text on a Status Line Assuming that the TD STS flag is set the following procedure should be used when displaying text on a status line 1Select the bottom status line shifted bottom status line or top status line by issuing a TCRT 1 54 1 55 or 1 63 command respectively 2Select the column where you wish to begin updating the status line by sending one of the encoded column specifiers from Table B 1 3Display text and attributes as desired 4End the status line update by issuing a TCRT 1 129 command This procedure should be repeated for all updates you wish to make AMOS Terminal System User s Guide Programming a Status Line Page 8 3 Some terminals will automatically exit the status line after all columns have been filled without requiring a TCRT 1 129 call Because not all terminals behave this way this behavior should not be depended on All status line calls should be terminated by a TCRT 1 129 call Note that only normal characters and attributes are allowed to be sent between the time a status line is selected via the TCRT 1 54 1 55 or 21 63 command and it is terminated by t
81. Watch4 Watch5 Watch6 Watch7 Watch8 15 159INQUIRE GRAPHICS CURSOR LOCATION TCRT 1 161 This call allows you to inquire the current state of the mouse without waiting for a button press or release Upon issuing a TCRT 1 161 call the AM 72 will send a report to the host giving the current location and button status The format of the report will be as described under TCRT 1 158 above AMOS Terminal System User s Guide Terminal Control Commands Page 15 45 15 160DEFINE GRAPHICS CURSOR REGIONS TCRT 1 162 To make it easy to adapt existing applications to use the graphics cursor the AM 72 allows you to specify up to 64 rectangular areas of the screen which will be sensitive to mouse button presses Any time a mouse button is pressed in a particular region a string which you have associated with that specific region will be sent to the host computer This allows you to adapt an application to mouse menu selection without the application needing any knowledge of mouse reports or other details To define graphics cursor regions start by issuing a TCRT 1 162 call Follow this with the number of regions you are defining encoded as defined in table F 3 of the AM 72 Programmer s Manual For each if the regions you wish to define now output the string to be sent upon a mouse press within the region and the corners of the rectangle you are defining The string is specified by sending in length of string as encoded by t
82. a Micro and because the AMOS system itself wishes to only see one type of interface a special piece of software called an interface driver is used to shield AMOS from the different hardware configu rations Once again the user and programmer can usually remain blissfully ignorant of the details of the interface driver It is mentioned here simply to make you aware of the many layers which comprise the terminal service system AMOS Terminal System User s Guide 2 2 How AMOS Interfaces to Terminals 2 3TERMINAL DRIVERS Now that AMOS has gotten data from the terminal through the serial interface and through the interface driver there is one last piece of software used to further shield your program from the many differences which exist in the real world of terminals This last piece is referred to as the terminal driver It is the terminal driver s job to translate your program s terminal commands to the special code sequences required by the terminal as well as to do any special processing of your keyboard input While in most cases the user and programmer can ignore the details of how the terminal driver works it is important to keep in mind that the entire terminal independence idea hinges on the use of a properly written terminal driver specifically written for the type of terminal in use used in concert with applications software written to observe the conventions and features of the terminal driver We hope such a t
83. able F 3 of the AM 72 Programmer s Manual followed by the characters of the string itself If you are using row column mouse reports specify the mouse sensitive rectangle by sending the row column coordinates fo the upper left and lower right corners of the rectangle The row and column are specified according to table F 1 of the AM 72 Programmer s Manual If you are using XY mouse reports specify the mouse sensitive rectangle by sending the XY coordinates of the upper left and lower right corners of the rectangle The XY coordinates are packed as described in Appendix A Continue outputting strings and rectangle definitions until all regions have been defined 15 1610UTPUT FORM FEED CHARACTER TCRT 1 163 This call outputs a form feed character ASCII 012 decimal at the current screen location If the terminal driver does not support this call nothing is output 15 1620UTPUT LINE FEED CHARACTER TCRT 1 164 This call outputs a line feed character ASCII 010 decimal at the current screen location If the terminal driver does not support this call nothing is output 15 1630UTPUT NEW LINE CHARACTER TCRT 1 165 This call outputs a new line character at the current screen location If the terminal driver does not support this call nothing is output 15 1640UTPUT VERTICAL TAB CHARACTER TCRT 1 166 This call outputs a vertical tab character ASCII 011 decimal at the current screen location If the terminal driver does not sup
84. ables both the underscore and the blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TDSUND and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 102END UNDERSCORED AND BLINKING TEXT TCRT 1 101 This call disables both the underscore and the blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occup
85. al System User s Guide 4 8 Principles of Effective Screen Design 4 5 6Status Lines Many terminals have additional screen display lines above and or below the main display area Typically known as status lines these areas remain even when the main screen area is cleared For this reason they are a convenient place to store information specific to the overall application rather than to the specific screen being displayed Relying on the presence of status lines however can cause problems if the application is run on a terminal without status lines 4 5 7Split Screen Some terminals have the capability of dividing the display area into two or more independent screen areas which may be individually cleared and scrolled This makes it convenient to implement screens formatted as multiple independent areas While split screen is a convenient implementation method for a specific type of screen design don t let the availability of split screens drive the screen design process Only use split screens if the information that must be displayed warrants it 4 5 8Color Some terminals have the ability to display different colors While this can be an excellent tool for effective screen design it also has its pitfalls Chapter 5 is devoted to the subject of color usage and how it can affect people s perceptions 4 5 9Graphics The addition of graphics to a terminal opens up a wide variety of options Even the simple line drawing charact
86. ally substituted 15 70PARAGRAPH CHARACTER TCRT 1 69 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 71DAGGER CHARACTER TCRT 1 70 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 72SECTION CHARACTER TCRT 1 71 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approxima
87. and TD PHR bits are set in the terminal capabilities flags 15 137SELECT CYAN TEXT TCRT 1 139 This command selects the current text color to be cyan on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 138SELECT BLACK REVERSE TEXT TCRT 1 140 This command selects the current text color to be the background color on a black background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development If the selected background color is black as is normal use of this function will produce invisible text This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags AMOS Terminal System User s Guide Terminal Control Commands Page 15 39 15 139SELECT WHITE REVERSE TEXT TCRT 1 141 This command selects the current text color to be the background color on a white background This function occupies one s
88. anges are made in such a way as to be upwardly compatible not forcing modification to software created prior to the change in the interface standard Of course this requirement in turn forces additional compromises forcing further changes thus creating a constantly evolving terminal environment This is not to say however that the terminal interface is a contantly changing amorphous mass Instead it evolves in distinct steps or levels as terminal technology advances Rather than changing constantly there really have been only three different levels of terminal support during the history of the Alpha Micro computer The first level dates back to the glass teletype days Here software had to assume the only features present were cursor addressing clear screen erase to end of line and erase to end of screen In actuality many of the terminals of that era did not even possess the erase to end of line and screen commands but instead required that these be simulated by the terminal interface software Next came the level where it could be safely assumed that in addition to the features listed above the typical terminal also contained insert and delete line capability dim mode and some special effects like reverse video or blinking With the introduction of the AM 60 terminal in 1983 we entered our third level of terminal interface Here it is considered likely that the terminal possesses all of the above features but also has func
89. ans a blue or red must be of much greater intensity than a minimum level green or yellow in order to be perceived 5 2 3After the Retina The optic nerve bundle leads from the photoreceptors at the back of the retina Along the optic nerve path at the lateral geniculate body the photoreceptor outputs recombine Figure 5 2 diagrams how this combination takes place Notice in Figure 5 2 that the original retinal channels red green and blue form three new opponent channels which are transmitted to the brain One channel signals the red to green ratio another the yellow to blue and the third indicates brightness Again we find a bias against blue since the perception of brightness and hence of edges and shapes is signaled by the red and green photpigments The exclusion of blue in brightness perception means that colors differing only in the amount of blue they contain will not produce sharp edges Neural organization into opponent channels has several other effects too The retinal color zones which link opponent red with green and opponent yellow with blue provide an example Opponent color linking prevents us from visually experiencing combinations of opposing colors Even though we can create light of the appropriate spectral mix we cannot experience reddish green or yellowish blue When we create a spectral mix of red and green the red to green ratio cancels out to zero while the yellow to blue ratio with its built in bias a
90. ard for the ANSI standard now offer terminals that support both the standard and an efficient mode The differences between these two modes can be quite dramatic a difference of 3 characters or 10 for exactly the same command Also all this standard did was partially delay the same old problems Because ANSI X3 64 is now several years old many terminals that claim to adhere to the standard also contain many extensions which of course are not standardized The standard also never addressed characters going from the terminal to the host as in function key input 1 3THE PHILOSOPHY OF TERMINAL DEVICE INDEPENDENCE After reviewing all of the possibilities outlined above and several others it became clear that a different approach had to be taken for the Alpha Micro computer system Intending to be around for a long time and requiring high performance from all parts of the system the existing solutions simply were not acceptable for the Alpha Micro computer The most important item in this entire book is the concept of terminal device independence Simply stated this concept allows the same applications software to be used on any terminal without requiring any modification to that software whatsoever This is accomplished by having the software perform all terminal functions through a common standardized interface While this interface will evolve as terminals themselves evolve it is always upwardly compatible allowing any software whic
91. arts and other special effects The character assignments are as follows Command Code Symbol Displayed 1 49 Solid block 1 50 Slanted line block 1 51 Cross hatch block AMOS Terminal System User s Guide Using the Alternate Character Set Page 11 3 11 4THE WORD PROCESSING CHARACTERS The word processing characters contain special characters typically used in an office environment The characters are as follows Command Code Symbol Displayed 1 64 Up arrow 1 65 Down arrow 1 66 Raised dot 1 67 End of line marker 1 68 Horizontal tab symbol 1 69 Paragraph symbol 1 70 Dagger symbol 1 71 Section symbol 1 72 Cent sign 1 78 One quarter symbol 1 74 One half symbol 1 75 Degree symbol 1 76 Trademark symbol 1 77 Copyright symbol 1 78 Registered symbol 11 5DEALING WITH CHARACTERS WHICH ARE NOT PRESENT Many terminals do not possess all or even any of the special characters described in this chapter In this case the terminal driver must attempt to emulate the characters by substituting characters it does have for the missing characters This can be very successful in the case of characters such as the line drawing symbols where the use of standard ASCII characters such as and instead of true line drawing characters works very well While the screen display may not be as attractive as when the line drawing characters are present no information content is lost
92. as no space attributes terminal has AM 70 color mode terminal has mode attributes instead of field terminal has draw and scroll box commands terminal has smooth scroll terminal has 80 132 column support terminal has printer support terminal has line insert delete terminal has character insert delete terminal has reverse video terminal has dim terminal has blink terminal has underscore terminal has erase to end of screen terminal has erase to end of line terminal has split screen terminal has status line terminal is an AlpghaTERMINAL terminal has multi key translation terminal has color capability terminal has column insert delete terminal has block fill terminal has alternate page AMOS Terminal System User s Guide 16 4 Assembly Language Terminal Drivers 16 1 1 10The TRMCHR Routine Transfer Vector TD TCH This word consists of a branch to the TRMCHR routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach 16 1 2The Terminal Driver Input Routine The input routine of the terminal driver receives all characters input from the terminal keyboard before they are passed on to the remainder of the terminal service system This gives the terminal driver an opportunity to intercept specific characters either translating them to one or more different characters or ignoring the keystroke altogether It is within the terminal driver input routine that multi keystr
93. as been described in general terms as it applies to the human visual system Yet all of us have our own perceptual ideosyncrasies that affect how we use color For example some people prefer highly saturated colors and other prefer muted ones It is important too to remember that color perception changes over time We adapt to color with prolonged viewing This results in an apparent softening of colors As a result there is a tendency to use highly saturated colors to offset adaptation The unadapted viewer however sees the colors as highly saturated Additionally some research indicates that pure colors are visually fatiguing Although we are still far from developing an aesthetics of color displays some information has been compiled on color combinations that go well together and those that do not Figures 5 3 and 5 4 present data from a study in which people were asked to pick the best and worst appearing colors on different backgrounds Choices were made for both thin lines and for larger filled panels The figures list those combinations preferred or rejected by at least 2596 of the subjects participating in the study While this was a small study and may not reflect the choices that would have been made by the people who will use your software it does provide a starting point for choosing color combinations Background Thin Lines and Text Thick Lines and Panels White Blue Black Red Black Blue Red Black White Yellow Yellow
94. ase the functionality of the new terminals by adding more sophisticated features such as cursor addressing and special erase commands Of course once someone had seen software which made use of these features nothing else was satisfactory so users were soon demanding these features And once one company had a terminal with one of the new features the competition needed to create a terminal with just one more feature to make theirs a bit better all of which resulted in providing the end user with a better more fully function ed terminal at a lower cost Everything sounds great right Well not quite Besides all of the benefits of competition in action we listed above one of its disad vantages was also in action As each manufacturer improved on its competition s terminal it also made some minor changes These minor changes were always made for the best of reasons efficiency cost reduction etc but they led to one inevitable result none of these new terminals were compatible with each other Users once having been exposed to them demand the advanced features present in these new terminals We are therefore forced to make application software which uses these features However the software written for one terminal will not function properly when used on a different terminal And terminals keep changing so often as they constantly improve we cannot afford to be stuck with only one type of terminal lest we be left behind our competition
95. ater in this chapter the printer port can also be used to connect a variety of serial devices to the host Examples of such devices might be alternate input devices such as mice trackballs and digitizers that would serve to augment the standard keyboard Because not all terminals contain a printer port a TRMCHR flag has been defined to denote the presence of the feature This flag must be checked prior to any attempt to use the printer port If this flag is not set and you use the printer port commands the results will be unpredictable 12 4 SCREEN PRINT While it might seem to be the simplest use of the printer port the Screen Print operation TCRT code 1 79 is actually one of the more complicated uses In theory all this command must do is cause an exact copy of the current screen display to be printed on the printer attached to the printer port However each terminal will execute this command based on its own unique idea as to what is appropriate to be sent to the printer Some terminals send every character at every screen location including attribute codes and nulls which may not be correctly interpreted by the local printer Others will replace non printing characters with spaces Some terminate each line with a carriage return while others send no line terminator at all In addition characters that are sent by the printer to the terminal may or may not be sent back to the host Some terminals do not accept keyboard input durin
96. atter cannot be overlooked however The issue of terminal indepen dence and how it is acheived if it is acheived at all can often make or break a software package determining whether it can successfully coexist with software already present on your system This book is intended to explore the various problems and possible answers and to present the set of solutions chosen by Alpha Micro as the best available based both on looking at where we came from as well as keeping an eye to the future Additionally it provides information on how you can design screen displays that are easier to use and more attractive based on sound human engineering principles While written primarily for software developers interested users of the Alpha Micro computer system with a general understanding of computers can benefit from reading Part of this book and quickly skimming Parts Il and Ill We wish to express our thanks to those members of the Alpha Micro community who gave their input and support to the effort culminating in this book By making hard decisions and sticking to those commitments they have made the jobs of all software developers easier and made the Alpha Micro a better system for all of its users AMOS Terminal System User s Guide PARTI GENERAL OVERVIEW AMOS Terminal System User s Guide CHAPTER 1 INTRODUCTION This book attempts to present a solution to a problem As evidenced by the size of the book the problem is not a s
97. ave unpredictable results AMOS Terminal System User s Guide Terminal Control Commands Page 15 43 15 153ENABLE PROPORTIONALLY SPACED TEXT TCRT 1 155 This call enables the display of proportionally spaced text All subsequent text output until a TCRT 1 156 call is displayed in the currently selected proportional font Available in AM 72 native modes only 15 154DISABLE PROPORTIONALLY SPACED TEXT TCRT 1 156 This call disables the display of proportionally spaced text Available in AM 72 native modes only 15 155SELECT COLOR PALETTE BY RGB VALUE TCRT 1 157 This call selects which of the 64 available colors you wish to select for the 16 color display palette You can change any of the 16 palette indices individually or as part of a group or you can reset the entire palette to its power up configuration For any of the 16 palette indices you can specify the desired color in terms of its RGB color value for selecting color palette indices based on HLS color specification see TCRT 1 177 To select a color index start by issuing a TCRT 1 157 call For each color index you wish to select output a color index and the desired R red G green and B blue color values You can repeat this process for as many color indices as you wish End the color selection process by sending a 177 octal 7F hex code The color index R G and B values are all output as eight bit integers using the packing method described in Appen
98. ay back on via the TCRT 1 37 command 13 6INSERT DELETE LINE CHARACTERS AND COLUMNS There are many times when a screen update consists simply of deleting an unwanted character or line from the screen or inserting a new character or line Instead of requiring that you redisplay large portions of the screen most terminals offer the ability to insert and delete individual characters and lines Text will automatically be moved to adjust for the insertion or deletion without requiring special programming to update the screen Some terminals also offer the ability to insert and delete columns of text AMOS Terminal System User s Guide 13 4 Miscellaneous Features Characters can be inserted and deleted via the TCRT 1 18 and TCRT 1 17 commands By positioning the character and issuing one of these calls text can be moved very quickly with a minimum of distracting screen redisplay Entire lines can be inserted and deleted via the TCRT 1 16 and TCRT 1 15 calls The character insert and delete functions are available only if the TD CID bit is set in the terminal capabilities word The line insert and delete functions are available only if the TD LID bit is set in the terminal capabilities word In addition to character and line manipulation some terminals offer the ability to insert and delete columns of text via the TCRT 1 88 and TCRT 1 89 calls These operations are analgous to the the line insert and delete functions b
99. ayed on the status line should then be sent Details on the use of status lines can be found in Chapter 8 After issuing this command and sending the column address and the desired text you must terminate the command by using the End Status Line functions TCRT 1 129 This function is available only if the TD STS bit is set in the terminal capabilities flags 15 57RESET TO DEFAULT DISPLAY FORMAT TCRT 1 56 This call resets the terminal to its normal power up display configuration in particular it removes all split screen segments rejoining the screen into a single segment and clears the screen If a particular terminal does not have this function this call will simply be ignored 15 58SET HORIZONTAL SCREEN SPLIT TCRT 1 57 This command allows you to divide the screen into two independent areas Each of these areas can be separately addressed cleared and otherwise worked with just as it were an entire screen You select which of these segments you wish to work with by using the TCRT 1 61 and 1 62 commands to select the active segment The active segment behaves just a a normal screen but does so without disturbing the other segment To select a horizontal split screen determine how many rows of characters you wish to have in the upper segment Use that number to determine the apporpriate height specification from Table B 5 Issue the TCRT 1 57 call and follow it with the character s from Table B 5 The screen will
100. be combined to generate specific hues This chapter will describe how both subtractive and additive color combinations work Finally we will discuss how colors can be described so that you can precisely specify the color you wish to use and the computer can generate the appropriate response 5 2THE PHYSIOLOGY OF COLOR In understanding how we see color it is important to realize that color is not a physical entity but is instead a sensation like taste or smell that is tied to the properties of our nervous system The light we see as colors is electromagnetic radiation with wavelengths ranging from approximately 400 nanometers to 700 nanometers covering the violet to red spectrum The color sensation results from the interaction of this light with a color sensitive nervous system While the frequency of the radiation being viewed by two people may be the same we must remember that those individuals can have vastly different color discrimination capabilities because of differences in the eye s lens its retina and other parts of the visual system Figure 5 1 shows the basic arrangement of the components of the human eye The lens focuses the image on the retina which in turn converts the light to electrochemical impulses carried by the optic nerve bundle to the brain Each of these elements in the perceptual chain contributes to the sensation we call color Sorry but this image could not be converted to Adobe Acrobat Format Please refer to
101. bing of the various display enhancements It is best for attention getting when the text to be highlighted becomes brighter than the other text although reversing this convention is also used 4 5 3Reverse Video The use of reverse video black characters on a light background has good attention getting capability but can reduce the legibility of the text so displayed Particularly on terminals where the screen brightness control has been adjusted too bright reverse video text may be hard to read It should not be used to excess on a screen or the display may suffer from the crossword puzzle effect where the areas of reverse video start to form patterns which distract from the information being presented 4 5 4Underlining Underlining is not a very good attention getter on terminal screens since the underline is usually placed so close to the characters that it tends to blend into the character reducing legibility Underlining can serve a useful function however by seperating areas of text 4 5 5132 Column Display Many modern terminals have the option of displaying the screen in a 132 column wide mode While this gives the ability to display increased amounts of information this is not usually an advantage The reduced legibility of the smaller characters combined with the danger of information overload make 132 column mode best suited for special applications such as spreadsheets or previewing printed reports AMOS Termin
102. ble from DSKO 7 0 JOBIDX A0 index job s JCB OV JOBTRM AO AO index job s TDB OV T TDV AO A0 index job s terminal driver OV A0O D FIL A4 get terminal driver name OVW AMX D EXT A4 Set extension OVW DSK D DEV A4 set DSKO CLRW D DRV A4 OVW lt 7_8 gt 0 D PPN A4 set 7 0 FETCH 4 1 load table and index with 1 AMOS Terminal System User s Guide Using Programmed Function Keys Page 9 3 9 3USING FUNCTION KEYS WITHIN YOUR APPLICATIONS SOFTWARE In order for your applications program to receive the special function key codes it must first perform two simple operations The first is to place itself into data terminal input mode by setting the T DAT flag octal 10 in the terminal status word It must then set the function key translation bit T XLT octal 40 in the terminal status word to enable the function key routines in the terminal driver Both of these status bits may be set in a single operation if desired Because use of the function keys requires that the program be in data mode it is best suited to those programs which receive and interpret keyboard input one character at a time This type of input is best characterized by programs such as AlphaVUE or the INPUT SBR portion of the AlphaACCOUNTING package When using function keys from higher level languages such as AlphaBASIC it will be necessary to perform the manipulation of the
103. ble lines begin writing to alternate page end writing to alternate page toggle page to alternate page select foreground color n select background color n select black text obsolete select white text obsolete select blue text obsolete select magenta text obsolete select red text obsolete select yellow text obsolete select green text obsolete select cyan text obsolete select black reverse text obsolete select white reverse text obsolete select blue reverse text obsolete select magenta reverse text obsolete select red reverse text obsolete select yellow reverse text obsolete select green reverse text obsolete select cyan reverse text obsolete select color palette by RGB value select color palette by HLS value AMOS Terminal System User s Guide AMOS Monitor TCRT Codes 14 1 2 15Miscellaneous Commands Page 14 9 TCRT 1 7 lock keyboard TCRT 1 8 unlock keyboard TCRT 1 19 read cursor address TCRT 1 20 read character at current cursor position TCRT 1 28 cursor on TCRT 1 29 cursor off TCRT 1 36 turn off screen display TCRT 1 37 turn on screen display TCRT 1 80 set to 132 column mode TCRT 1 81 set to 80 column mode TCRT 1 120 set cursor to blinking block TCRT 1 121 set cursor to steady block TCRT 1 122 set cursor to blinking underline TCRT 1 123 Set cursor to steady underline TCRT 1 148 save a rectangular area TCRT 1 149 restore a rectangular
104. built into some terminals simply aren t available in a conversational terminal Protected fields also are limited in their usefulness when dealing with any form that requires more than one screen to present They are also being squeezed out by such features as color and graphics where it is of limited use to be able to clear everything but the red stuff or clear everything but the blue circles For this reason care should be taken when designing new applications to make sure that by using protected fields you are not limiting your ability to use future terminals that will not contain protected field capabilities AMOS Terminal System User s Guide 7 2 Protected Fields 7 1THE PROTECTED FIELD COMMANDS Protected fields are implemented through the use of the TCRT 1 13 TCRT 1 14 and TCRT 1 11 TCRT 1 12 pairs of commands Protected fields affect the operation of the commands TCRT 1 0 1 9 and 1 10 7 1 1Enabling and Disabling Protected Fields The terminal commands TCRT 1 13 and 1 14 are used to enable and disable protected fields respectively Once protected fields have been enabled any text that has been written in the dim protected mode is protected from erasure via the Clear Screen TCRT 1 0 Clear to End of Line TCRT 1 9 and Clear to End of Screen TCRT 1 10 commands Disabling protected fields returns the terminal to normal operation where the erase commands clear all text d
105. characteristics of the terminal driver These bits are TD LCL This terminal has local echo TD NEW This is a new driver in that it contains header entries and routines for initialization impure size and flags There should be very few old drivers left anywhere TD TCH This driver contains a TRMCHR routine TD NTD This driver is not a real terminal driver This flag is used by the AMOS Installation Program when initially configuring a system It has no meaning outside of that process and can otherwise be ignored 16 1 1 2The Input Routine Transfer Vector TD INP This word consists of a branch to the input routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach 16 1 1 3The Output Routine Transfer Vector TD OTP This word consists of a branch to the output routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach 16 1 1 4The Echo Routine Transfer Vector TD ECH This word consists of a branch to the echo routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach 16 1 1 5The TCRT Routine Transfer Vector TD CRT This word consists of a branch to the TCRT routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach 16 1 1 6The Initialization Routine Transfer Vector TD INI This word consists of a branch to the
106. characters will cause the characters to be displayed with the screen attribute Writing additional characters before the begin attribute character or after the end attribute character will cause them to be displayed normally In a mode terminal all characters you write to the screen are written with the screen attribute corresponding to the current mode you are in Upon entering reverse video mode for example all characters you write will be displayed in reverse video regardless of their location This will continue until you select a different attribute mode for writing 3 2 1Compatibility Issues Field terminals are still the most common as they were the first type of terminal to be widely used Most of the very latest terminals however are being built as mode terminals Because of the differences in the behavior of these two terminal types special care must be taken when creating software which must run on both types an important feature because terminals are likely to switch from field to mode terminals almost entirely over the next few years 3 2 1 1To Space or Not to Space One of the major differences between mode and field terminals is how the attributes themselves appear on the screen In a field terminal the attribute typically occupies a Screen position appearing as a space a non hidden attribute In a mode terminal however the attribute is typically invisible and does not occupy a screen position a hidden attribute
107. consisting of your specified string the row and column the mouse is currently positioned on encoded as shown in table F 1 of the AM 72 Programmer s Manual followed by the button status The button status can be decoded by subtracting 32 From the returned character and using the remianing value as a binary button mask where the low order bit corresponds to the status of button1 the next bit button 2 etc You can also select mouse reports to the returned with XY coordinates in a 32 767 by 32 767 world space This is done by sending a W in place of the C described above All subsequent position reports will return the current X and Y locations in place of the row and column positions described above The X and Y values are packed as described in Appendix A 15 157DISABLE GRAPHICS CURSOR TCRT 1 159 This call disables the graphics cursor The cursor itself is removed from the screen and any subsequent button manipulation will not send position reports 15 158SELECT GRAPHICS CURSOR SHAPE TCRT 1 160 This call allows you to select the shape of the graphics cursor There are 16 different shapes to choose from To select a cursor shape issue a TCRT 1 160 call followed by the single character code for the desired cursor shape from the table below space White arrow Black arrow Pointing hand Four way arrow 96 Two way arrow horizontal amp Two way arrow vertical Pencil Watch1 Watch2 Watch3
108. creen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 140SELECT BLUE REVERSE TEXT TCRT 1 142 This command selects the current text color to be the background color on a blue background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 141SELECT MAGENTA REVERSE TEXT TCRT 1 143 This command selects the current text color to be the background color on a magenta background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 142SELECT RED REVERSE T
109. cursor one column to the left If the cursor is positioned in column 1 when this call is made the cursor will wrap around and be positioned in the rightmost column one row above where it was before the call was made If the cursor is in column 1 row 1 of the current screen segment when this call is made the cursor will be positioned on the last column of the last row Otherwise this call does not affect the screen display 15 7CURSOR RIGHT TCRT 1 6 This call moves the cursor one column to the right If the cursor is positioned in the last column of a row when this call is made the cursor will wrap around and be positioned in the leftmost column one row below where it was before the call was made If the cursor is in the last column of the last row of the current screen segment when this call is made the call will cause the Screen to scroll up one line and the cursor will be positioned in column 1 of the last screen line Otherwise this call does not affect the screen display If the screen scrolls then the top line is considered lost Although some terminals contain buffers larger than one screen and allow text scrolled off the top to be retreived this is a terminal dependent feature and should not be relied upon 15 8LOCK KEYBOARD TCRT 1 7 This call disables the keyboard preventing the operator from sending further input to the computer This call is normally used in conjunction with the TCRT 1 8 call described below
110. d For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 104 function but does not occupy a screen position This function is available only if the TD UND TD RVA TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 118END UNDERSCORED REVERSE BLINKING TEXT W O A SPACE TCRT 1 117 This call disables the underscore reverse video and blinking text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 105 command but does not occupy a screen position This function is available only if the TD UND TD RVA TD BLK and TD NSP bits are set in the terminal capabilities flags AMOS Terminal System User s Guide 15 34 Terminal Control Commands Because this command cannot be supported by many terminals presently installed p
111. d method of color selection uses two ranges of TCRT calls the 2 and 3 ranges to allow independent specification of foreground and background colors using as many as 256 different colors Not only does this method offer the most flexible selection of colors and color combinations but it also does not require a screen position to change colors allowing full utilization of the screen display space AMOS Terminal System User s Guide 10 2 Programming Color Terminals 10 3 1Selecting Foreground Color To select the foreground display color use the command TCRT 2 n where the value n can range from 0 to 255 decimal This selects the color in which text will be displayed against the selected background color The value n is one of colors available from the color map discussed above If you specify a color which is not available on the particular terminal in use the closest available color will be used The TCRT 2 n command does not occupy a screen position Further color selected via this command should be treated as a mode attribute 10 3 2Selecting Background Color To select the background display color use the command TCRT 3 n where the value n can range from 0 to 255 decimal This selects the color of the background against which the foreground color will be displayed The value n is one of colors available from the color map discussed above If you specify a color which is not available on the part
112. d on a blue background all reverse video text would be displayed as blue foreground characters on a white background This function is available only if the TD UND and TD RVA bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 104END UNDERSCORED AND REVERSE VIDEO TEXT TCRT 1 103 This call disables both the underscore and the reverse video text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD UND and TD RVA bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not b
113. dard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags AMOS Terminal System User s Guide 15 38 Terminal Control Commands 15 135SELECT YELLOW TEXT TCRT 1 137 This command selects the current text color to be yellow on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 136SELECT GREEN TEXT TCRT 1 138 This command selects the current text color to be green on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR
114. de terminals AMOS Terminal System User s Guide Introduction to Terminals Page 3 3 which would not normally exhibit the screen flash problem 1 Position the cursor at the end of the area to be written with text 2lssue an end attribute command for the attribute you are going to be using Mode terminals will ignore this 3Position the cursor at the beginning of the area to be written with text 4lssue a begin attribute command for the attribute you wish to use This will start the attribute for both mode and field terminals 5Write the text 61 an end attribute command again This will end the attribute for mode terminals AMOS Terminal System User s Guide PART Il DESIGNING EFFECTIVE SCREEN DISPLAYS AMOS Terminal System User s Guide CHAPTER 4 PRINCIPLES OF EFFECTIVE SCREENDESIGN That the software we develop should be easy to use seems obvious it goes without saying Yet the computer industry has acquired a reputation for creating systems and products that are difficult frustrating and tedious to use While undoubtedly deserved in some cases this reputation does no one any good Only by creating systems that are a pleasure to use will we be able to eradicate this image This chapter will show some of the things we can do to try to acheive this goal 4 1WHAT WE ARE LOOKING FOR Of course the ideal system has probably not yet been built And yet partly through experience with bad systems we can
115. dix A of the AM 72 Programmer s Manual The RGB values for the 64 available colors are shown in Appendix G of that manual To reset the color palette to its power up configuration issue a TCRT 1 157 call and immediately follow it with a 176 octal 7E hex code This resets the color palette and terminals the palette selection command It is best to reset as many palette as possible with a single TCRT call in order to eliminate display artifacts such as flashing or unpleasant color combinations 15 156ENABLE GRAPHICS CURSOR TCRT 1 158 This call enables the graphics cursor The selected cursor shape see TCRT 1 160 will be displayed on the screen and will track the movements of the mouse a report will be sent to the host computer giving the current location and button status The format of this report is described below To enable the graphics cursor start by issuing a TCRT 1 158 call Follow this with a C to select row column coordinates Next send it the string you wish to have sent to you at the start of each graphics cursor report Specify this string by sending the number of characters in the string followed by the string itself The number of characters is encoded as shown in table F 3 of the AM 72 Programmer s Manual AMOS Terminal System User s Guide 15 44 Terminal Control Commands Each time a mouse button is pressed or released or you specifically request a report the AM 72 will send a graphics cursor report
116. dling all serial IO for the system AMOS Terminal System User s Guide AMOS Terminal System User s Guide 132 column mode 80 column mode achromatic color AlphaBASIC alternate character set alternate page AM 70 ANSI standard ASCII character set ASCII terminal operation attribute attributes blinking block fill bold box fill bright cce eimi See eo bcr atr Ae See ea qa normal reverse video status line terminal underline Aux port bidirectional Bidirectional print blinking block fill attribute character block graphics block mode box attribute codes AMOS Terminal System User s Guide Page Index 1 INDEX 2 3 15 1 11 1 14 6 15 6 to 15 7 15 11 to 15 14 15 18 to 15 21 B 5 13 2 14 8 15 22 to 15 23 6 1 14 5 4 7 6 1 8 8 15 6 15 9 to 15 10 15 27 to 15 29 15 31 to 15 34 13 1 15 24 4 7 6 2 10 2 4 7 6 1 7 2 8 3 15 3 E 1 3 2 15 29 to 15 34 E 1 15 3 4 7 6 2 8 3 10 2 15 9 to 15 10 15 28 to 15 33 E 2 8 3 B 3 15 7 4 7 6 1 8 3 15 8 15 27 to 15 30 15 32 to 15 33 15 48 Page Index 2 AMOS Terminal System User s Guide Double lines 15 42 sei 15 24 15 42 Rounded corners 15 42 scrolling a paw hee awe ERG 15 25 SiZe GOdes cenit eer oe ste ese Bane tus Wicd se B 6 Window style 15 42 box drawing
117. duce confusion Avoid the need for color discrimination in small areas Hue information is lost for small areas In general two adjacent lines of a single pixel width will merge to produce a mixture of the two Also the human visual system produces sharper images for achromatic colors Thus for fine detail it is best to use black white and gray while reserving chromatic colors for larger panels or for attracting attention 5 5 3Cognitive Guidelines Do not overuse color Perhaps the best rule is to use color sparingly The benefits of color as an attention getter information grouper and value assigner are lost if too many colors are used Cognitive scientists have shown that the human mind experiences great difficulty in maintaining more than five to seven elements simultaneously so it is best to limit displays to about six clearly discriminable colors Group related elements by using a common background color Cognitive science has advanced the notion of set and preattentive processing In this context you can prepare or set the user for related events by using a common color code A successive set of images can be shown to be related by using the same background color Similar colors connote similar meanings Elements related in some way can convey that message through the degree in similarity in hue The color range from blue to green is experienced as more similar than the range from red to green Along these same lines saturation
118. e This will make the visual results match those of a field terminal AMOS Terminal System User s Guide 16 10 Assembly Language Terminal Drivers 16 2 3Full Emulation of Non Existent Features Beyond the simple emulations described above are a host of full blown emulations which attempt to simulate advanced terminal features as best they can In most cases there is little advantage to doing so as the application software should be written to adapt itself to the missing features In some circumstances such as where a terminal is missing some fundamental feature or where a particular application program does not properly adapt itself to a missing feature or does not bother to check to see if the feature is available it may be desirable to attempt emulation Such emulations range from the relatively simple clear to end of line or clear to end of Screen to the more complex box drawing and area fill commands to the very complex emulating an addressable status line on a terminal with only a non addressable status line Because such emulations vary widely in their implementation due to differences in the particular terminal in use this section will not detail the specific methods that can be used Such emulations are typically more trouble than they are worth and mention is made of them only for completeness and to offer them as a possible solution when all else fails Remember that characters output to terminal from within
119. e this capability 8 1 2Status Line Addressability The first programmable status lines available all required that the programmer redisplay the entire status line each time any information on the status line changed This posed no problem for information such as the name of a program or the system date due to the infrequent updates required However when used to display information such as the current time or the current row and column position within an editor requiring the entire status line to be constantly updated imposed a large amount of terminal communications overhead In addition because the status line typically was cleared each time it was selected the status line appeared to flash each time it was updated For this reason addressable status lines were developed With an addressable status line it becomes possible to update any portion of the status line without disturbing the remaining areas This is done by specifying a starting column number whenever the status line needs to be updated By starting at a specific column changing as few characters as possible and then ending the update a small portion of the status line can be modified quickly without annoying screen flash All of the status lines supported by the standard terminal interface are assumed to be addressable If a particular terminal does not support addressable status lines such operation must be emulated by software contained within the terminal driver 8 2
120. e Retina ro e 5 4 5 2 4 5 5 4 5 3 PRINCIPLES OF 2 8 eens 5 5 5 3 1 Perception is Nonlinear 5 5 5 3 2 Perception of Achromatic Color 5 6 5 3 3 Perception of Chromatic 5 6 5 3 4 Colors in Context 5 7 5 3 5 Individual 5 lt 5 8 5 4 COGNITIVE PRINCIPLES 0 00 c cece tees 5 9 5 5 GUIDELINES FOR EFFECTIVE COLOR USE 5 10 5 5 1 Physiological Guidelines 5 10 5 5 2 Perceptual Guidelines 5 11 5 5 3 Cognitive Guidelines 5 12 5 6 COLOR MIXTURE hh 5 13 5 6 1 Subtractive Color 5 13 5 6 2 Additive Color Mixture 5 14 5 7 DESCRIBING COLORS 00000 tenes 5 15 5 7 1 The Hue Lightness Saturation Model of 5 16 5 7 2 The Alpha Micro Eight Bit Color 5 17 CHAPTER 6 SCREEN DISPLAY ATTRIBUTES 6 1 DIMINTENSII Y 252 pont ree alah eL eden ee oreet ER ed psg odes 6 1 6 2 UNDERLINE htt Rete ese et
121. e current cursor location Screen areas are saved in a stack within the terminal in a last in first out fashion That is the most recent area to be saved is the one that will be restored by the next Restore Area command You can restore a saved area to a screen position other than the one it was saved from although extreme care must be taken to make sure that the desired results are achieved particularly in field attribute emulations Restoring an area with a different size than the one it was saved with will yield unpredictable results Not available in Esprit Ill emulation 15 148ENTER FULL GRAPHICS MODE TCRT 1 150 This call is used to switch from text mode to graphics mode when using AM 62A or AM 70 emulations It is not required but is ignored by the AM 72 native modes This call clears the screen and prepares the terminal for graphics display instead of text display 15 149EXIT FULL GRAPHICS MODE TCRT 1 151 This call is used to switch from graphics mode to text mode when using AM 62 or AM 70 emulations It is not required but is ignored by the AM 72 native modes This call clears the screen and prepares the terminal for text display instead of graphics display AMOS Terminal System User s Guide 15 42 Terminal Control Commands 15 150DRAW A BOX WITH ROUNDED CORNERS TCRT 1 152 This command allows you to draw a box on the screen This box encloses a rectangular area of the screen with line drawin
122. e programs to have unpredictable results on terminals which fully implement color selection and attributes AMOS Terminal System User s Guide 11 USING THE ALTERNATE CHARACTERSET In addition to the standard 96 displayable ASCII characters many terminals contain additional characters and symbols that can be displayed on the screen These additional characters include line drawing characters block graphics characters and special word processing symbols These additional characters are said to belong to an alternate character set This chapter describes these various symbols and how to display them on the terminal in a completely terminal independent method 11 1USING THE ALTERNATE CHARACTER SET Once again we are in a situation where different terminals handle things with a wide variety of methods This section will describe a terminal independent way of displaying alternate characters Typical methods employed by terminal manufacturers for displaying symbols from the alternate character set include hiding the alternate characters in the normally non displayable control characters preceding special characters with a special lead in code or having a special alternate character set mode where the actual meaning of all characters change To make software that works with all of these methods the following procedure should be followed whenever alternate character set symbols are to be displayed 1 Position the cursor to
123. e that the lone cool color green represents a different type of data AMOS Terminal System User s Guide Using Color Effectively Page 5 11 Note that many of these cognitive principles can be used to your advantage For example using the tendency to group colors into warm and cool classifications can serve a useful grouping function in an appropriately designed graph However it is important that you be aware of the principles to avoid accidentally running afoul of them 5 5GUIDELINES FOR EFFECTIVE COLOR USE As we have noted color can be an extremely useful tool in helping to differentiate data The human eye can differentiate between approximately 25 colors with no reference and over 20 000 colors when they are placed next to each other This provides for a very rich method of encoding data However the use of color can also be very tiring to the operator by causing eyestrain Such eyestrain can result from the physical aspects of the terminal such as the highly reflective Screen often found on color terminals or it may be caused by a choice of colors which causes frequent re focusing of the eye In addition the use of colors which violates our unconcious assumptions about the meanings of color can lead to increased error rates and even mental stress Only through the careful application of color can we be sure that we gain the maximum advantage of its use without incurring its penalties On the basis of the preceding discussio
124. e turned off by using the TCRT 1 14 call described below If a particular terminal does not support this function this call is simply ignored 15 15DISABLE PROTECTED FIELDS TCRT 1 14 This call disables protected fields After issuing this call all information on the screen is subject to erasure by any one of the screen erase commands Detailed information on the operation of protected fields may be found in Chapter 7 of this manual If a particular terminal does not support this function this call is simply ignored 15 16DELETE LINE TCRT 1 15 This call causes the line of text the cursor is currently positioned on to be deleted All rows starting from the row immediately below the cursor row to the last row of the current screen segment are moved up one row row of blanks appears as the new bottom line The cursor position is unaffected This call is not available when protected fields are enabled This function is available only if the TD LID bit is set in the terminal capabilities flags 15 17INSERT LINE TCRT 1 16 This call causes a blank line to be inserted at the current cursor row It causes all rows starting from the row the cursor is positioned on to the last row in the current screen segment to be moved down one row row of spaces is inserted at the original cursor row and the cursor is positioned at the start of that row This call is not available when protected fields are enabled This function i
125. e will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 50SOLID BLOCK CHARACTER TCRT 1 49 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available an or character is normally substitu ted AMOS Terminal System User s Guide 15 14 Terminal Control Commands 15 51SLANTED LINE BLOCK CHARACTER TCRT 1 50 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available an or character is nor
126. ear the inside of the box the use of the Block Fill with Character command TCRT 1 91 is recommended To draw a box first position the cursor at the upper left corner of the box Issue a TCRT 1 92 call followed by height and width codes taken from Table B 5 The screen display will then be updated 13 7 2Scrolling Boxes Two commands allow you to scroll a rectangular area of the screen by copying that area up or down one line This is useful when using a rectangular area of the screen as a window onto text AMOS Terminal System User s Guide Miscellaneous Features Page 13 5 To scroll an area of the screen up one line first position the cursor at the upper left corner of the area to be scrolled Issue a TCRT 1 93 call followed by height and width codes taken from Table B 5 The text within the rectangle will now be moved up one line Note that the last line in the rectangle has been duplicated by the copy operation If you wish the last line to be cleared your program must perform that operation itself To scroll an area of the screen down one line first position the cursor at the lower left corner of the area to be scrolled Issue a TCRT 1 94 call followed by height and width codes taken from Table B 5 The text within the rectangle will now be moved down one line Note that the first line in the rectangle has been duplicated by the copy operation If you wish the first line to be cleared your program must perform that o
127. ecifies the area for which you wish to set the attribute and the second which specifies the attribute you wish to place there The first argument byte consists of a single ASCII character either 0 1 or 2 A 0 selects the data text entry portion of the screen display A 1 selects the terminal message field portion of the upper status line The terminal message field is where you see the CAPS indicator when you depress the CAPS LOCK key A 2 selects the program message field of the top status line The second argument is an attribute code taken from Table B 2 This call is used to select attributes for the top status line and the text data entry area only To set the attribute for the bottom status line position the cursor to the first position on the bottom status line and embed the appropriate control character to acheive the desired result as described in the section on TCRT 1 54 If a particular terminal does not have this function this call and the following attribute characters will simply be ignored AMOS Terminal System User s Guide 15 8 Terminal Control Commands 15 29MAKE CURSOR VISIBLE TCRT 1 28 This call turns on the cursor and makes it visible once again This call is used in conjunction with TCRT 1 29 below to hide the cursor during screen update This produces a more pleasant screen display than one where the cursor is flashing around on the screen If a particular terminal does not su
128. ed by an End Status Line TCRT 1 129 command Details on the use of status lines can be found in Chapter 8 This command is similar to the TCRT 1 55 command but only allows writing to the entire status line without individually addressable columns This makes this command less efficient than the TCRT 1 55 command but is supported by a wider variety of terminals The size of the status line referenced by this command may be found via the TRMCHR monitor call This function is available only if the TD STS bit is set in the terminal capabilities flags 15 130SELECT BLACK TEXT TCRT 1 132 This command selects the current text color to be black on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development AMOS Terminal System User s Guide Terminal Control Commands Page 15 37 If the selected background color is black as is normal use of this function will produce invisible text This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 131SELECT WHITE TEXT TCRT 1 133 This command selects the current text color to be white on the standard background This function occupies one screen position and is therefore conside
129. ed is blue Green is reported across a broader range of 500 to 550 nm and yellow across a narrow band around 570 to 580 nm Above 610 nm most persons report the sensation red The best or purest color defined as those containing no trace of a second color would indicate pure blue at 470 nm pure green at 505 and pure yellow at 575 nm Hue then is the basic component of color It is the primary determinant for a specific color sensation Although hue is closely related to certain wavelengths remember that hue is a psychological variable and wavelength a physical one Although people with normal color vision will name a sector of the visual spectrum as red they will disagree about the reddest red or where red becomes orange Such disagreement reflects varying experiences with color as well as differences in each person s visual system AMOS Terminal System User s Guide 5 8 Using Color Effectively Saturation is most closely related to the number of wavelengths contributing to a color sensation As the band of wavelengths narrows the resulting sensation becomes more saturated the wider the band the less saturated the color Conceptually a scale of saturation can be envisioned as extending from a pure hue such as red through less distinct varients of the hue such as shades of pink to a neutral gray in which no trace of the original hue is noticed By taking a neutral color and determining the amount of a pure hue we mu
130. een position On terminals which do not have this character available a character is normally substituted 15 40TOP RIGHT CORNER CHARACTER TCRT 1 39 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 431BOTTOM LEFT CORNER CHARACTER TCRT 1 40 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 42BOTTOM RIGHT CORNER CHARACTER TCRT 1 41 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the norma
131. elationship to the draw box command areas can be scrolled whether surrounded by a box or not 15 95SCROLL BOX DOWN ONE LINE TCRT 1 94 This command allows you to scroll a rectangular area of the screen by copying that area down one line This is useful when using a rectangular area of the screen as a window onto text To scroll an area of the screen down one line first position the cursor at the lower left corner of the area to be scrolled Issue a TCRT 1 94 call followed by height and width codes taken from Table B 5 defining the lower right corner of the area to be scrolled The text within the rectangle will now be moved down one line Note that the first line in the rectangle has been duplicated by the copy operation If you wish the first line to be cleared your program must perform that operation itself All validation of the size of the box to be scrolled is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will have unpredicatable results This function is available only if the TD BOX bit is set in the terminal capabilities flags It has no other relationship to the draw box command areas can be scrolled whether surrounded by a box or not 15 96SELECT JUMP SCROLL TCRT 1 95 This call selects the jump method of scrolling text off of the screen In this mode each line simply disappears off the top of the screen to be replaced w
132. en the TRMCHR routine is called the following registers will be set up D2 Contains the flags specified on the TRMCHR call A1 Indexes the user s argument block A2 Indexes the current terminal driver A5 Indexes the terminal control block for this terminal The following registers are available for use by the TRMCHR routine All others must be saved and restored by the routine if they are to be modified A1 A2 A6 D2 D6 D7 The TRMCHR routine must fill in all fields in the users argument block If the TC BMP flag is set in D2 then the TRMCHR routine must also return the TCRT code availability bitmap AMOS Terminal System User s Guide 16 8 Assembly Language Terminal Drivers The fields that must be returned by the TRMCHR routine in all cases are TC FLG TC ROW TC COL TC CLR TC FGC TC BGC TC WNR TC WNC Longword specifying the terminal capabilities as described in section 16 1 1 9 of this chapter Word specifying the number of rows currently available on the terminal screen Note that the value returned in this field may vary depending on the current mode the terminal is in Word specifying the number of columns currently available on the terminal screen Note that the value returned in this field may vary depending on the current mode the terminal is in Word specifying the number of different colors available on the terminal A value of zero in this field is assumed to mean a monochrome terminal
133. ent and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 106END UNDERSCORED REVERSE VIDEO BLINKING TEXT TCRT 1 105 This call disables the underscore reverse video and blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD RVA and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 107START UNDERSCORED TEXT W
134. er of being replaced by new information Its capacity is about seven items Remembering a telephone number long enough to dial it taxes the memory of many people Clearly this memory should not be relied upon for screen design The human ability to learn is important it is what differentiates people from machines A screen design developed with the intent of minimizing human learning time can accelerate human performance Given enough time of course people can improve their performance in almost any task Most people can be taught to walk a tightrope but a designer should not call for a tightrope if a walkway is feasible Most learning is a combination of trial and error and insight Learning can be enhanced if it allows skills acquired in one situation to be used in another somewhat similar situation Design consistency accomplishes this provides complete and prompt feedback s phased that is requires a person to know only that information needed at that point in the learning process 4 4 2Screen Format and Content Clarity meaningfulness and ease of use of a screen display is achieved through the format and content of the display itself and the information contained in the display The format and content of the display will be determined by where information is placed how information is structured and what information is included The guidelines that follow provide general rules addressing these questions Provide an obvi
135. er sets available on most terminals allow a variety of capabilities including segmenting screen regions via boxes lines etc Care must be taken however to avoid making things worse by having the graphic elements be what is focused on Make sure that the graphic elements you add are in support of the information on the screen and do not overwhelm it A full graphics capability opens up possibilities which are too varied and numerous to be discussed here As full graphics terminals become more widespread additional attention to screen design for them will be needed 4 6IMPLEMENTING GOOD SCREEN DESIGNS It is just about impossible to follow every one of these rules in a particular design Likewise the field of human factors study is rapidly evolving as more people begin to understand the importance of the field and more research is performed So rather than taking the information we have outlined as graven truth it should instead be viewed as a series of guidelines that can help you to design your own set of rules for screen formatting For example during the development of the AlphaWHRITE word processing system an understanding of the principles we have outlined led to the following guidelines for screen displays being set up AMOS Terminal System User s Guide Principles of Effective Screen Design Page 4 9 eAll screens have a title summarizing the purpose of the particular screen displayed on the top line centered in reverse video
136. erences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD BLN bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 24ENABLE ALTERNATE CHARACTER SET TCRT 1 23 This call enables the display of the alternate character set This call must be used prior to using the calls TCRT 1 38 through TCRT 1 53 and TCRT 1 64 through TCRT 1 78 When the alternate character set is enabled displayable characters may only be sent to the terminal via the TCRT calls listed above Normal output of displayable characters will produce unpredictable results You may however use other TCRT calls and output positioning codes including RETURN LINE FEED and the cursor positioning call This call is used in conjuction with TCRT 1 24 to enable the alternate character set display some characters then re
137. ereotypes red for warning green for go and yellow for attention Since we all have experience with these meanings maintaining the relationship maps nicely into our expectations In color coding graphed measurement data variation of hue can quickly communicate important information Portions of the data within a certain tolerance or range limit can be coded green portions approaching a limit can be yellow and excesses can be coded red This procedure fits into the normal cognitive expectations For multiple graphs where color is simply used to differentiate between data sets contrast is a big consideration As a result it is tempting to use red for one line and green for another While this makes the data readily distinguishable which is the goal it can also bias a viewer toward making some quality judgements about the data the red data are bad or dangerous the green are okay Such biasing of the viewer might not be what you intended Similarly the perceived magnitude of different colors varies A red square will be perceived as being larger than a green one of identical size In a situation such as an area graph this can be extremely misleading Combinations of colors may be perceived as defining groupings of data that you did not intend For example consider a graph which consists of 4 lines one yellow one red one orange and one green An observer may tend to group the warm colors yellow red and orange together and assum
138. erminal driver is already available and installed on your system If not later sections of this book describe how to create a terminal driver This task is best left to an experienced systems programmer however 2 4STANDARDIZED TERMINAL INTERFACE Via the different layers we have described AMOS creates a standardized terminal interface for your program isolating your program from the many different terminals it may have to function with This standardized interface has two main features your program will use the TCRT calls and the TRMCHR call 2 4 1The Monitor TCRT Calls The individual functions the terminal driver supports are implemented via the TCRT call This call passes the user s terminal command whether a cursor position or a clear screen to the terminal driver where it is translated into the special code sequence required by the particular terminal The TCRT call takes two arguments row and column The row argument has a value range of 127 to 128 and the column argument has a value range of 0 to 255 Whenever the row argument is positive the row and column arguments are treated as a cursor position and the cursor is moved to the position specified by the arguments When row is negative the column argument is taken as a special function code and interp reted accordingly The most common negative value of row is 1 which corresponds to the most commonly used set of terminal functions Other negative values are used to f
139. f nulls to delay until the clear screen operation is finished This should have no effect on any software using this call 15 2CURSOR HOME TCRT 1 1 This call moves the cursor to row 1 column 1 of the current screen segment but does not otherwise affect the screen display 15 3CURSOR RETURN TCRT 1 2 This call moves the cursor to column 1 of the current row but does not otherwise affect the screen display AMOS Terminal System User s Guide 15 2 Terminal Control Commands 15 4CURSOR UP TCRT 1 3 This call moves the cursor up one row If the cursor is currently positioned on the top row of the current screen segment the cursor will wrap around and be positioned on the last row of the current segment Otherwise this call does not affect the screen display 15 5CURSOR DOWN TCRT 1 4 This call moves the cursor down one row If the cursor is positioned on the bottom row of the current screen segment when this call is made it will cause the screen display to be scrolled up one line and the cursor will remain positioned on the bottom row of the current screen segment Otherwise this call does not affect the screen display If the screen scrolls then the top line is considered lost Although some terminals contain buffers larger than one screen and allow text scrolled off the top to be retreived this is a terminal dependent feature and should not be relied upon 15 6CURSOR LEFT TCRT 1 5 This call moves the
140. fect the text in the currently selected segment AMOS Terminal System User s Guide 13 2 Miscellaneous Features This capability can be very useful when you are displaying two seperate types of information These two types may be two different documents status information and data or any other combination of text that you wish to be able to update independent of each other Most terminals that support split screen only allow the split to be done in the horizontal dimension that is you can divide the screen into upper and lower segments A very few terminals allows you to divide the screen vertically into left and right segments So few terminals support this vertical split capability however that its use should be avoided except for very specialized applications where the reduction in terminal independence is not critical Commands are provided to split the screen into upper and lower segments at any line A segment can be as small as a single line or as large as one line less than the height of the screen The upper segment is referred to as segment 0 and the lower is referred to as segment 1 You select a horizontal split screen by issuing the TCRT 1 57 call and following it with the number of rows you wish segment 0 to contain in a coded format Details on using this call can be found in Chapter 15 Splitting the screen will clear both segments Once the screen has been split you can select one segment or the other by using
141. g graphics characters This command differs from TCRT 1 92 in that the box has rounded rather than square corners Note that only the outside lines of the box are drawn on the screen characters inside and outside the box are unaffected by this command If you wish to clear the inside of the box the use of the Block Fill with Character command TCRT 1 91 is recommended To draw box first position the cursor at the upper left corner of the box Issue a TCRT 1 152 call followed by height and width codes taken from Table B 5 which define the lower right corner of the area The screen display will then be updated All validation of the size of the box to be drawn is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will have unpredictable results 15 151DRAW A WINDOW STYLE BOX TCRT 1 153 This command allows you to draw a box on the screen This box encloses a rectangular area of the screen with line drawing graphics characters This command differs from TCRT 1 92 in that the box shape has been specifically designed to be attractive when used as a pop up window Note that only the outside lines of the box are drawn on the screen characters inside and outside the box are unaffected by this command If you wish to clear the inside of the box the use of the Block Fill with Character command TCRT 1 91 is recommended To draw a box first positio
142. g the print operation while others may send keyboard input either to the host or to the printer or both As can be seen using the printer port is not necessarily a simple matter However most of the work in creating a working combination of host software terminal and printer is in choosing compatible items To maintain compatibility between a wide variety of terminal printer combinations emphasis should be placed on acquiring the correct terminal and printer rather than customizing the host software since this defeats any device independence AMOS Terminal System User s Guide 12 2 Using the Printer Port One area of concern is error recovery during a print operation Because some terminals lock out the keyboard during a print operation if the printer should fault e g out of paper there is no simple way to regain control of the application software from the keyboard For this reason timeouts or other escape mechanisms should be built into software which makes extensive use of the local printer capability 12 2TRANSPARENT PRINT The second method of using the printer port is known as transparent print In this mode all characters the host sends to the terminal are immediately sent to the printer without any effect on the terminal screen A program causes the terminal to enter transparent print mode by issuing the Enter Transparent Print Mode call TCRT 1 82 Once all desired data has been sent to the printer the prog
143. h as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 145SELECT CYAN REVERSE TEXT TCRT 1 147 This command selects the current text color to be the background color on a cyan background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 146SAVE A RECTANGULAR AREA TCRT 1 148 This call saves a rectangular area of the screen in an off screen buffer within the AM 75 It is intended to be used to save an area of the screen which is to be overlaid with a pop up menu and later restored when the menu is removed Using this call removes the requirement for applications software to maintain its own screen image greatly increasing the speed of display and reducing the communications overhead of using pop up menus Screen areas are saved in a stack within the AM 75 in a last in first out fashion That is the most recent area to be saved is that one that will be restored by the next Restore Area command TCRT 1 149 To use this call issue a TCRT 1 148 call fol
144. h properly uses the standard interface to continue to function regardless of the particular terminal and its capabilities After accepting a command from a program through this standardized interface the command is passed to the terminal driver program It is the responsibility of this driver program to translate the command into the specific command sequence required by a given terminal As we have said before achieving this goal of terminal independence is not a simple task even though the concept itself is simple enough It requires a rigid adherence to a particular set of rules However because software is written only once while terminals change far more rapidly the initial investment of effort in adhering to the rules is much smaller than the continual modification necessary if the software is written to be terminal dependent In the discussion thus far we have concentrated on the commands that must be transmitted from the host to the terminal Equally important to any application package is the information that goes from the terminal to the host such as function key input Both directions must be standardized in order to completely insulate the software from the terminal The important thing to remember is that by maintaining terminal independence you preserve your investment in application software and ensure you benefit from the improved price performance supplied by future terminals 1 4 PHILOSOPHY BEHIND ALPHA MICRO TERMINAL
145. hange the sense of foreground and background When reverse video is in effect changing the foreground color via the TCRT 2 n call will affect the background of the displayed text Likewise changing the background color will affect the foreground of the displayed text This affect is undone by the end reverse video command AMOS Terminal System User s Guide Programming Color Terminals Page 10 3 Let s look at some examples To take the simplest case first assume that the current colors are yellow foreground text on a black background Selecting the reverse video attribute will cause all subsequent text to be displayed as black characters on a yellow background Ending the reverse video attribute will cause subsequent text to once again be displayed as yellow characters on a black background Lets see what happens when we start with yellow on black select reverse video and then change the foreground color to red via a TCRT 2 n call In this case subsequent text will be displayed as black characters on a red background Furthermore ending the reverse video attribute will cause later characters to be displayed as red on black 10 3 5Maintaining the Default Foreground and Background Colors Programs which change the foreground and background colors must be careful to restore the user s selected foreground and background colors upon exiting Because each user may have a particular choice of colors which may be wildly different from your o
146. he other hand because of the shift in the sensitivity of the eye AMOS Terminal System User s Guide 5 12 Using Color Effectively The magnitude of a detectable change in color varies across the spectrum Small changes in extreme reds and purples are more difficult to detect than small changes in other colors such as yellow and blue green Also our visual system does not readily perceive changes in green Difficulty in focusing results from edges created by color alone Our visual system depends on a brightness difference at an edge to effect clear focusing Multicolored images then should be differentiated on the basis of brightness as well as of color Avoid red and green in the periphery of large scale displays Because of the insensitivity of the retinal periphery to red and green these colors in saturated form should be avoided especially for small symbols and shapes Yellow and blue are good peripheral colors With the common terminal screen of 14 inches diagonal or so peripheral vision is not usally relied upon to the extent where this would be a concern Opponent colors go well together Red and green or yellow and blue are good combinations for simple displays The opposite combinations red with yellow or green with blue produce poor images For color deficient observers avoid single color distinctions Colors which differ only in the amount of red or green added or subtracted from the two other primaries may p
147. he TCRT 1 129 call Any other characters or TCRT commands will cause unpredictable results 8 3STATUS LINE ATTRIBUTES Status lines use a different method of selecting display attributes than the rest of the screen Rather than using TCRT calls to select the dim and bright attributes special single character codes are used instead Anytime that you write text to one of the status lines you can select whether you want the text displayed in dim or bright mode To select dim mode text precede the text with a hex 1F byte To return to normal mode text send a hex 1E byte To avoid having to select dim or bright mode each time text is written to the status line you can set the default mode for the status line by using the appropriate TCRT code to select the desired status line and then sending a 1E or 1F byte in place of the column code normally used This will set the default display mode for the status line A TCRT 1 129 should immediately follow this sequence Any additional text sent to the status line will now be displayed in the selected mode unless specifically overridden by sending a 1E or 1F code Other attributes such as reverse video underscore etc are also implemented differently on status lines than they are in the other areas of the screen Rather than using specific TCRT codes to turn these attributes on and off special control characters must be sent to change the current attribute setting These special control codes are sh
148. he remaining colors are specified around the perimeter of the cone with magenta at 60 red at 120 yellow at 180 green at 240 and cyan at 300 Complementary colors are 180 apart Lightness L is represented as the vertical axis of the double cone It is given a value varying between 0 and 1 At L 0 we have black At L 1 we have white The gray scale is along the L axis with the pure hues in the L 0 5 plane The saturation parameter S specifies the relative purity of a color This parameter also varies between 0 and 1 Pure hues are those for which S 1 and L 0 5 As S decreases the hues are said to be less pure At S 0 we have the gray scale AMOS Terminal System User s Guide 5 18 Using Color Effectively This model allows you to think in terms of making a selected hue darker or lighter A hue is selected with hue angle and the desired shade tint or tone is selected by adjusting L and S Colors are made lighter by increasing L and made darker by decreasing L When S is decreased the colors move toward gray 5 7 2The Alpha Micro Eight Bit Color Map Using the HLS color description system we can describe a virtually unlimited number of different colors Of course the display equipment we will be using to display the specified color is far more limited Likewise some programs simply need to be able to specify a color without regard to the subtleties of color mapping systems For this reason
149. hree primaries with 1 00 as the maximum value The HLS values are given in standard HLS notation See Chapter 5 for more information on the HLS System The text color description is an attempt to describe the color in descriptive terms As with any descriptive system its fault lies in the many variables that may affect the reproduction of a particular color such as display brightness ambient light etc These descriptions are intended as a guide only AMOS Terminal System User s Guide 2 Color Number OONDOABRWN O 0 00 1 00 0 00 1 00 1 00 1 00 0 00 0 00 0 33 0 67 0 00 0 67 0 67 0 67 0 00 0 00 0 33 0 67 0 00 0 33 0 33 0 33 0 00 0 00 0 33 0 67 0 33 0 67 1 00 0 67 0 00 0 00 0 67 0 33 0 00 1 00 1 00 1 00 0 33 0 00 1 00 0 67 0 33 1 00 1 00 1 00 0 33 0 00 1 00 0 00 0 00 0 00 1 00 1 00 1 00 0 33 0 67 0 00 0 00 0 00 0 67 0 67 0 67 0 33 0 67 0 00 0 00 0 00 0 33 0 33 0 33 0 67 1 00 0 00 0 00 0 00 1 00 1 00 1 00 0 33 0 67 0 33 0 00 0 33 0 67 1 00 0 67 0 67 1 00 0 33 0 33 0 33 1 00 1 00 0 00 1 00 1 00 1 00 0 00 0 00 0 00 1 00 0 33 0 67 0 67 0 67 0 00 0 00 0 00 0 67 0 67 1 00 0 33 0 33 0 00 0 00 0 00 0 33 0 33 0 67 1 00 1 00 0 33 0 00 0 33 0 67 0 33 0 67 1 00 0 67 0 00 0 00 0 00 1 00 0 67 1 00 1 00 1 00 0 33 0 33 0 33 The Alpha Micro Color Map Table C 1 The Alpha Micro Color Map H L S Description
150. icular terminal in use the closest available color will be used The TCRT 3 n command does not occupy a screen position Further color selected via this command should be treated as a mode attribute 10 3 3Dealing with Color and Non Color Terminals The color selection TCRT commands are ignored on monochrome terminals This allows you to place color selection commands in your software without requiring that you check to see if color is available on your terminal In cases where you wish the software to behave differently depending on whether color is available or not your program can check the TD CLR bit in the terminal capabilities flags returned by TRMCHR This flag will be set for color terminals In addition TRMCHR returns the number of colors available 10 3 4Combining Color and Other Display Attributes Color can be combined with other display attributes such as underlining or reverse video to create a wide variety of effects that enhance the appearance of the screen display In most cases the combination of color and other attributes is straightforward For example selecting underline on a color terminal will simply display the underline in the foreground color Selecting blinking text on a color terminal will blink the foreground color Combining these attributes requires no special action on the programmer s part Reverse video however is somewhat of a special case When you select reverse video on a color terminal you c
151. ight background the effect is reversed On a color terminal reverse video will simply exchange the background and foreground colors serial A method of data transfer between a computer and a peripheral device such as a terminal in which data is transmitted bit by bit over a single circuit terminal The primary device used to communicate between the computer and yourself Especially a CRT terminal or video display terminal with a keyboard and television like Screen or a hard copy terminal with a keyboard and associated printer terminal control block TCB The data structure within the terminal service system which is used to maintain the current status of a terminal as well as its input and output buffers Each terminal defined on a system has a terminal control block associated with it whether it is attached to a job or not terminal driver A machine language program which translates data from internal formats to a format understood by a particular terminal terminal service system The part of AMOS responsible for coordinating and handling all serial for the system Among its responsibilites are the buffering of both input and output characters scheduling of jobs as they enter and leave terminal wait states and servicing of all user requests for terminal input and output TRMSER an acronym for the terminal service system contained within AMOS The terminal service system is responsible for coordinating and han
152. im or not but does not change the appearance of the screen display 7 1 2Selecting Text as Protected Text that is to be protected from erasure once protected fields are enabled must be written in dim reduced intensity mode To begin writing text in dim mode issue a TCRT 1 11 command Once the desired text has been displayed you may return to writing normal text by issuing a TCRT 1 12 command Note that some terminals require that you issue the Enable Protected Fields command TCRT 1 13 prior to writing any protected text 7 2USING PROTECTED FIELDS Because terminals vary widely in the precise interaction of the Dim commands and the Enable Protected Field commands the following procedure should be used to eliminate any terminal dependent situations 1 Plan on writing the entire protected area in one pass and the unprotected areas in second pass 2Prepare the screen for the protected area by erasing the area first via the Clear Screen Clear to End of Line or Clear to End of Screen commands 3 Turn on protected fields via the TCRT 1 13 command 4 Turn on the Dim mode via the TCRT 1 11 command When the protected fields mode is enabled this command might be thought of as the Write protected characters command rather than just the Dim command 5 Position the cursor on the screen and display the characters that you wish to have protected from erasure 6 Turn off Dim mode via a TCRT 1 12 command AMOS Terminal
153. imple one We hope however that as you read it you will gain an appreciation not only of the problem but also of the many benefits associated with the solution 11 STATEMENT OF THE PROBLEM The problem we wish to address in this book has ancient roots at least as far as the computer industry goes Back in the very early days of interactive computing there was the Teletype ASR 33 terminal This was a hardcopy printing terminal that had a top speed of 10 characters per second had only upper case characters and could do nothing more complex than simply put characters down on a piece of paper Its only redeeming quality was that it was available in quantity and was inexpensive relative to the times at a cost of several thousand dollars As the market for interactive computing grew and as the cost of integrated circuits fell there came an opportunity to replace the venerable ASR 33 with something better What became available next was a very simple CRT video terminal which did nothing more than emulate an ASR 33 at somewhat lower cost and somewhat higher speed In fact these early CRT terminals were often referred to as glass teletypes These terminals emulated the ASR 33 so well in fact that all of the old software written for the ASR 33 worked just fine on the new CRT terminals No problem so far right Well as the market grew and the cost of electronics continued to plummet some enterprising engineers started to see ways to incre
154. in the terminal capabilities flags NOTE Very few terminals support the use of a vertical split screen and because of the complexity of the operation it is very unlikely that the operation will be supported via software emulation within the terminal driver For these reasons any use of this command increases terminal dependence and is therefore not recommended 15 60SET VERTICAL SCREEN SPLIT W 40 CHARACTERS TCRT 1 59 This command allows you to divide the screen into two independent areas Each of these areas can be separately addressed cleared and otherwise worked with just as it were an entire screen You select which of these segments you wish to work with by using the TCRT 1 61 and 1 62 commands to select the active segment The active segment behaves just a a normal screen but does so without disturbing the other segment This command splits the screen into two vertical halves of 40 characters each The cursor will appear only in the active segment However whenever a segment is selected the cursor will return to the position within the segment where it was last located The screen will stay split until a TCRT 1 56 is issued This function is available only if the TD SPL bit is set in the terminal capabilities flags NOTE Very few terminals support the use of a vertical split screen and because of the complexity of the operation it is very unlikely that the operation will be supported via software emulation within the te
155. ine is being executed at interrupt level it is vital that it be made as efficient as possible to avoid adverse impact on system performance AMOS Terminal System User s Guide Assembly Language Terminal Drivers Page 16 5 16 1 3The Terminal Driver Echo Routine The echo routine of the terminal driver receives all characters which are to be echoed back to the user The terminal driver is given control to allow different echoing styles for different terminals For example a video terminal may echo a rubout as a backspace space backspace sequence removing the character from the screen printing terminal however may echo a rubout by backspacing and overstriking lt is up to the terminal driver echo routine to determine the behavior of echoed characters While rubouts tabs and control U are the characters most commonly echoed specially there is nothing to prevent a terminal driver from treating either more or fewer characters as special cases When the echo routine is called the following registers will be set up D1 Contains the character to be echoed A5 Indexes the terminal control block for this terminal The following registers are available for use by the echo routine All others must be saved and restored by the routine if they are to be modified AO A2 A6 D1 D2 D3 D6 D7 If no special action is taken by the terminal driver routine the character to be echoed should be returned in D1 and the Z bit reset If the termi
156. ing on whether a given color is blue or green AMOS Terminal System User s Guide 5 6 Using Color Effectively Sorry but this image could not be converted to Adobe Acrobat Format Please refer to your printed manual for this picture Figure 5 2 Processing of Color Input into Opponent Channels While serious forms of color deficiency exist less than one tenth of 196 of the male population actually has problems discerning differences in the types of colors used on terminal displays While this can be a very important consideration in life critical applications such as nuclear reactor control systems aerospace navigation systems or medical monitoring equipment most of the environments we will be developing software for need not consider color blindness as a major constraint 5 3PRINCIPLES OF PERCEPTION Perception refers to the process of sensory experience Although perception is most certainly a product of our nervous system adequate information about the higher order function does not exist to describe perception in physiological terms As a result psychological methods must be relied on the most valuable discipline being psychophysics Psychophysics is a discipline that seeks to describe objectively how we experience the physical world around us 5 3 1Perception is Nonlinear Psychophysical research has shown that practically all perceptual experiences are nonlinearly related to the physical event For example the relati
157. ing the P command in Setup Mode to toggle ports For more information on the AM 65 s serial ports see the AM 65 Reference Guide 15 183SELECT 8 BIT CHARACTER DISPLAY TCRT 1 185 For terminals which support both 8 bit character sets such as ISO Latin 1 and 7 bit National Replacement Character NRC sets this call selects the 8 bit character set for all subsequent character displays 15 184SELECT 7 BIT CHARACTER DISPLAY TCRT 1 186 For terminals which support both 8 bit character set such as ISO Latin 1 and 7 bit National Replacement Character NRC sets this call selects the 7 bit character NRC set for all subsequent character displays AMOS Terminal System User s Guide Terminal Control Commands Page 15 49 15 185SELECT 8 BIT KEYBOARD MODE TCRT 1 187 For terminals which support both 8 bit character set such as ISO Latin 1 and 7 bit National Replacement Character sets this call causes the keyboard to generate the 8 bit character set for all subsequent keystrokes 15 186SELECT 7 BIT KEYBOARD MODE TCRT 1 188 For terminals which support both 8 bit character set such as ISO Latin 1 and 7 bit National Replacement Character sets this call causes the keyboard to generate the 7 bit character set for all subsequent keystrokes 15 187SELECT PRIMARY PRINTER PORT TCRT 1 189 When using a workstation as a terminal emulator this call selects the first printer port e g LPT1 as the port to receive all o
158. initialization routine of the terminal driver If a branch will not reach it must be coded as a branch to a jump which will reach AMOS Terminal System User s Guide Assembly Language Terminal Drivers Page 16 3 16 1 1 7The Impure Area Size TD IMP This word defines the number of bytes to be allocated as impure space for this terminal A pointer to this impure space will be placed in the longword field T IMP within the terminal definition block defining this terminal Such impure space is useful for storing the current values of such items as current color or current screen width Because terminal drivers are shared and must therefore always be coded as pure and re entrant this impure space is the only permanent storage available to the terminal driver routines 16 1 1 8The Row and Columns Sizes TD ROW and TD COL These fields are obsolete and should not be used All software must use the TRMCHR call to determine the height and width of the terminal screen 16 1 1 9The Terminal Capabilities Word TD FLG This longword field contains a number of single bit flags which describe the capabilities of the terminal TC FLG TD GRA TD NSP TD PHR TD MOD TD BOX TD SMT TD 132 TD PRT TD LID TD CID TD RVA TD DIM TD BLN TD UND TD EOS TD EOL TD SPL TD STS TD AMS TD MLT TD CLR TD KID TD BLF TD ALP It is these flags that are returned by the TRMCHR call in the field terminal supports full graphics capability terminal h
159. ion occupied by the begin attribute command is displayed as a normal space with no attributes The attribute does not take affect until the next character Likewise the end attribute command is displayed as a normal space with no attribute being displayed AMOS Terminal System User s Guide Screen Display Attributes Reverse and blink Underscore and blink Underscore and reverse Underscore reverse and blink And for attributes without embedded spaces Reverse and blink Underscore and blink Underscore and reverse Underscore reverse and blink AMOS Terminal System User s Guide Begin 1 34 1 100 1 102 1 104 Begin 1 110 1 112 1 114 1 116 End 1 35 1 101 1 103 1 104 End 1 111 1 113 1 115 1 117 Page 6 3 CHAPTER 7 PROTECTED FIELDS Protected fields are simply areas of the screen display protected from erasure by the normal clear Screen commands Protected fields were originally designed for use with block mode terminals used on mainframe computers where there was no capability of providing a truly interactive environment because of the low data communications rates and the general batch or transaction orientation of such computers The majority of applications software consists of displaying a request for information accepting a response validating and storing the response and then once again requesting the same item In a block mode environment then it seems logica
160. is followed by a carriage return character If a particular terminal does not support this function this call is simply ignored Note that this may cause problems as the software issuing the call will be stuck waiting for a response to the command A software timeout can be used to help alleviate this problem NOTE Use of this call is not recommended due to the small number of terminals which support this function While this command could be emulated by the terminal driver by having the driver keep track of the current cursor position the complexity of the rules which any given terminal follows in positioning the cursor make this a very complex task It is therefore likely that the effort and code space required to implement such an emulation make it more trouble than it is worth 15 21READ CHARACTER AT CURSOR POSITION TCRT 1 20 This call allows a program to request the character occupying the row and column where the cursor is currently located The program issuing this call must wait for a single byte to be returned by the terminal If a particular terminal does not support this function this call is simply ignored Note that this may cause problems as the software issuing the call will be stuck waiting for a response to the command NOTE Use of this call is not recommended due to the small number of terminals which support this function Because emulation of this feature would require the terminal driver to keep a screen i
161. ith the new line It is the opposite of smooth scrolling where the text of the line is rolled off the top of the screen one character dot at a time AMOS Terminal System User s Guide 15 26 Terminal Control Commands Smooth scrolling is generally considered to be more visually pleasing than jump scrolling but restricts the rate at which information can be scrolled on the screen Therefore it is usually used under special circumstances rather than as the normal mode of operation Calls are provided TCRT 1 96 through TCRT 1 99 for up to four different smooth scrolling rates This function is available only if the TD SMT bit is set in the terminal capabilities flags If a particular terminal does not have this function this call will simply be ignored 15 97SELECT FAST SMOOTH SCROLL TCRT 1 96 This call selects the fastest of the available smooth scrolling modes See the information on TCRT 1 95 for more information on smooth scrolling This function is available only if the TD SMT bit is set in the terminal capabilities flags If a particular terminal does not have different settings for smooth scroll but instead offers only the choice between jump scroll and one speed of smooth scrolling this call will select smooth scrolling 15 98SELECT MEDIUM FAST SMOOTH SCROLL TCRT 1 97 This call selects the second fastest of the available smooth scrolling modes See the information on TCRT 1 95 for more information on smo
162. ixture Colors can be mixed in another fashion in which bands of wavelengths are added to one another In fact this method of additive color mixture forms the underlying principle by which the visual system mixes colors Additive color mixing is also the means by which color is produced on a color terminal screen The surface of a typical color terminal screen is made up of thousands of tiny dots of phosphor The phosphors on the screen are grouped into threes called triads with one phosphor emitting long wavelength light red one emitting middle wavelength light green and the third emitting short wavelength light blue To display a red character on the screen all the red phospors forming the outline and interior of the character are made to emit light A green or blue character would be produced in the same manner Intermediate hues to red green and blue are produced by simultaneously making two or more of the three phosphors in a triad emit light Because the phosphor dots are very small when viewed from a distance the output of the three members of the triad fuse together forming a mixture of the phosphor outputs The result is a homogenous appearing field of color Causing both the red and green phosphors to emit light will result in a yellow hue The exact color of the yellow will depend on the relative intensities of the red and green phosphors Increasing the amount of red while decreasing the green would move the color towa
163. l If the terminal is already in 80 column mode no operation is performed Programs using this call must assume that the screen display is cleared when this call is issued even though not all terminals will clear the screen To reduce the possiblity of an improper Screen display appearing the entire screen should be cleared prior to issuing this call In addition to changing the screen format this call also changes the value which will be returned for number of columns when a TRMCHR call is issued This function is available only if the TD 132 bit is set in the terminal capabilities flags 15 83ENTER TRANSPARENT PRINT MODE TCRT 1 82 This call enables the transparent print function on those terminals which have local printer support Once this call has been issued all further data sent to the terminal will be routed to the printer port and will be ignored by the terminal display When the terminal has been placed in transparent print mode the only command it will then recognize is the command to exit the transparent print mode TCRT 1 83 This function is available only if the TD PRT bit is set in the terminal capabilities flags 15 84EXIT TRANSPARENT PRINT MODE TCRT 1 83 This call disables the transparent print function that was enabled by the TCRT 1 82 call After issuing this call all data sent to the terminal will once again be interpreted as commands or data to be displayed on the screen as appropriate This func
164. l Driver Input 16 4 16 1 3 The Terminal Driver Echo 16 5 16 1 4 The Terminal Driver Output Routine 16 5 16 1 5 The Terminal Driver TCRT Routine 16 6 16 1 6 The Terminal Driver Initialization Routine 16 7 16 1 7 The Terminal Driver TRMCHR Routine 16 7 16 2 EMULATING FEATURES NOT AVAILABLE ON YOUR TERMINAL 16 8 16 2 1 Substituting One Feature for Another 16 9 16 2 2 Emulation by Combining 16 9 16 2 3 Full Emulation of Non Existent Features 16 10 APPENDIX A ASCII CHARACTER CHART APPENDIX B CODE SUMMARIES AMOS Terminal System User s Guide AMOS Terminal System User s Guide Page vii APPENDIX C THE ALPHA MICRO COLOR MAP APPENDIX D FUNCTION KEY TRANSLATION TABLES D 1 STANDARD FUNCTION KEY TRANSLATION TABLES D 2 SET PFK STYLE TRANSLATION TABLES APPENDIX E GLOSSARY INDEX AMOS Terminal System User s Guide AMOS Terminal System User s Guide Page ix PREFACE Surprisingly the subject of computer display terminals can often be a controversial one the many variations present in available terminals combined with the aesthetic judgments required to determine when a display looks right often lead to unproductive arguments The importance of the subject m
165. l cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 45LEFT INTERSECTION CHARACTER TCRT 1 44 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 46BOTTOM INTERSECTION CHARACTER TCRT 1 45 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted AMOS Terminal System User s Guide Terminal Control Commands Page 15 13 15 47HORIZONTAL LINE CHARACTER TCRT 1 46
166. l character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted AMOS Terminal System User s Guide 15 12 Terminal Control Commands 15 43TOP INTERSECTION CHARACTER TCRT 1 42 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 44RIGHT INTERSECTION CHARACTER TCRT 1 43 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call wil
167. l to move as much as possible of the responsibility of displaying the request and accepting and validating the response into the terminal thus freeing up the host computer This was done by making the software create a form on the screen which would be filled in by the operator Not until the entire form has been accepted and validated was anything sent to the host Once everything was satisfactory the entire form s worth of information would be sent at once as in all block mode operation To further reduce the data communications requirements it was attractive to only send the underlying form once rather than for each request The problem is once the form is filled out and transmitted how do you erase the old information in preparation for the new request without erasing the form itself The answer of course is protected fields By designating the form as protected it became possible to clear only the operator s responses without touching the form display This became a very popular method of dealing with block mode terminals It was not long however before someone discovered that you could use the same technique with conversational mode terminals Information would be transmitted on a character by character basis but the form would not have to be repainted This level of use of protected fields within a conversational interactive environment is still valid However all of the fancy editing and validation capabilities that were
168. lable on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted AMOS Terminal System User s Guide Terminal Control Commands Page 15 15 15 55SELECT UNSHIFTED BOTTOM STATUS LINE TCRT 1 54 This command selects the bottom unshifted status line as the place to receive subsequent text After issuing this TCRT call you must send a column position where you wish the text to begin This column position can be selected from Table B 1 After sending the column position the text to be displayed on the status line should then be sent Details on the use of status lines can be found in Chapter 8 After issuing this command and sending the column address and the desired text you must terminate the command by using the End Status Line functions TCRT 1 129 This function is available only if the TD STS bit is set in the terminal capabilities flags 15 56SELECT SHIFTED BOTTOM STATUS LINE TCRT 1 55 This command selects the bottom shifted status line as the place to receive subsequent text After issuing this TCRT call you must send a column position where you wish the text to begin This column position can be selected from Table B 1 After sending the column position the text to be displ
169. lable only if the TD UND and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 109START REVERSE VIDEO TEXT W O A SPACE TCRT 1 108 This call enables the reverse video text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 32 function but does not occupy a screen position This function is available only if the TD RVA and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 110END REVERSE VIDEO TEXT W O A SPACE TCRT 1 109
170. lag different commands Therefore when we speak of TCRT 1 12 we are describing a specific terminal function in the row 1 range and the specific command of 12 AMOS Terminal System User s Guide How AMOS Interfaces to Terminals Page 2 3 2 4 2The TRMCHR Call The TRMCHR terminal characteristics call provides a standardized way for programs to determine the characterisitics of the terminal they are dealing with TRMCHR returns such information as the current size of the screen in rows and columns the features contained within the terminal the current color selections and several other descriptive items By providing this one method information can be formatted and returned by the terminal driver in a consistent manner regardless of what operations may be necessary to obtain the information 2 4 3Higher Level Language Interfaces to the Terminal In addition to the assembly language monitor calls interface we have discussed most of the higher level languages provide ready access to the terminal interface system AlpbhaBASIC for example provides access to the TCRT calls themselves throughs its PRINT TAB statement and provides access to the TRMCHR information via an XCALL subroutine TRMCHR SBR Other languages provide similar interfaces It is important regardless of the language that all software have access to the standard terminal interface provided by TCRT and TRMCHR to allow us to achieve our goal of terminal inde
171. lowed by the dimensions of the area to be saved encoded the same as the fill area and scroll area commands from Table B 5 The saved area extends from the current cursor location for the number of rows and columns specified The total number of characters that may be saved in all Save Area commands can be found by doing a TRMCHR call and looking at the TC SVA field a word value giving the total number of AMOS Terminal System User s Guide Terminal Control Commands Page 15 41 bytes that can be saved at any one time Note that this field contains a static value representing the total memory available for this purpose and is not updated as saves and restores are performed The amount of memory available for the stack is affected by the number of lines and columns being displayed whether Dual Sessions is enabled and whether the Graphics Cartridge is installed It is fairly safe to assume that in any mode there will be sufficient memory to save one 80x24 page Areas that are saved remain valid until the screen scrolls is cleared or a Remove Split Screen command is executed Not available in Esprit Ill emulation 15 147RESTORE A RECTANGULAR SCREEN AREA TCRT 1 149 This call allows you to restore a rectangular area of the screen which has previously been saved by a TCRT 1 148 call To restore the most recently saved area issue a TCRT 1 149 call followed by the dimensions of the area to be restored The area will be restored at th
172. mage in memory it is not likely that this feature would ever be emulated in software AMOS Terminal System User s Guide 15 6 Terminal Control Commands 15 22START BLINKING TEXT TCRT 1 21 This call enables the blinking text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD BLN bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 23END BLINKING TEXT TCRT 1 22 This call disables the blinking text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the diff
173. mally substitu ted 15 52CROSS HATCH BLOCK CHARACTER TCRT 1 51 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available an or character is normally substitu ted 15 53DOUBLE HORIZONTAL LINE CHARACTER TCRT 1 52 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a character is normally substituted 15 54DOUBLE VERTICAL LINE CHARACTER TCRT 1 53 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not avai
174. more information the more competition for the user s attention Visual search times will be longer and meaningful patterns more difficult to create Provide all data related to one task on a single screen One should not have to remember data from one screen to the next Short term memory is limited in capacity and unreliable All necessary information should be available on the screen Present information in directly usable form Do not require reference to documentation translations transpositions interpolations etc The computer is far better at performing such conversions than any person is Let the computer do the work Guide a person through the screen with implicit or explicit lines formed by display elements By carefully arranging the screen display the user s eye can be led to the next field to be used Visual appearance and usage should be consistent If the appearance is consistent the user does not need to learn new information for each screen reducing training time For text use lower case with the initial sentence letter in upper case Studies have shown that the use of mixed upper and lower case greatly aids in comprehension and recognition of words due to the larger number of symbol shapes available AMOS Terminal System User s Guide 4 6 Principles of Effective Screen Design Use standard alphabetic characters to form words or captions Specialized computer characters especially when rendered in dot ma
175. n because each terminal has been designed with a unique set of editing capabilities over which the host has no control it becomes exceedingly difficult to overcome these differences and provide a terminal independent environment For example a given block mode terminal may only support the insert or delete character operations affecting an entire line and thus be unable to use them when several fields occur on the same line of the screen Applications software which uses block mode is also hard to integrate with the majority of other AMOS software which is conversational mode based For all of these reasons block mode is not often used with AMOS and its use with new applications is discouraged 3 2FIELD VS MODE TERMINALS Terminals handle screen display attributes such as underscore reverse video or blinking in one of two ways field or mode In a field terminal you begin an attribute field by issuing a special command From that point on progressing left to right down the screen all text on the screen will be displayed using the new attribute until either the end of the screen is hit or another attribute is encountered You can think of these attributes as being special characters which turn on and turn off the screen AMOS Terminal System User s Guide 3 2 Introduction to Terminals attribute as the text is displayed on the screen Writing additional characters to the screen between the begin and end attribute
176. n the cursor at the upper left corner of the box Issue a TCRT 1 153 call followed by height and width codes taken from Table B 5 which define the lower right corner of the area The screen display will then be updated All validation of the size of the box to be drawn is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will have unpredictable results 15 152DRAW A BOX WITH DOUBLE LINES TCRT 1 154 This command allows you to draw a box on the screen This box encloses a rectangular area of the screen with line drawing graphics characters This command differs from TCRT 1 92 in that the box has double lines surrounding the box area rather than single lines Note that only the outside lines of the box are drawn on the screen characters inside and outside the box are unaffected by this command If you wish to clear the inside of the box the use of the Block Fill with Character command TCRT 1 91 is recommended To draw a box first position the cursor at the upper left corner of the box Issue a TCRT 1 154 call followed by height and width codes taken from Table B 5 which define the lower right corner of the area The screen display will then be updated All validation of the size of the box to be drawn is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will h
177. nal driver does its own echoing setting the Z bit before returning will prevent the terminal service system from performing its default echo processing Because the echo routine is called at interrupt level the routine does not have a job context and is restricted as to the monitor calls it can issue Specifically you cannot issue SLEEP TTY TTYI or any other call requiring a job context In addition because this routine is being executed at interrupt level it is vital that it be made as efficient as possible to avoid adverse impact on system performance 16 1 4The Terminal Driver Output Routine The output routine of the terminal driver receives all characters which are to be output to the terminal This gives the terminal driver an opportunity to intercept specific characters either translating them to one or more different characters or ignoring the character altogether When the output routine is called the following registers will be set up D1 Contains the character to be output A5 Indexes the terminal control block for this terminal The following registers are available for use by the output routine All others must be saved and restored by the routine if they are to be modified AO A2 A3 A6 D1 D2 D3 D6 D7 The output character is returned to the terminal service system in D1 If a simple substitution is to take place the new character should simply be placed in D1 AMOS Terminal System User s Guide 16 6
178. nately no one set of guidelines can cover all applications Up to now color has been used almost exclusively in a qualitative rather than a quatitative fashion that is showing that one item is different from another rather than showing relationships of degree A typical example might be in multi layer printed circuit board design where each layer is assigned a different color The colors serve to separate the layers visually on the screen but say nothing about the relationships between the layers By assigning the colors in spectral order using the ever popular ROY G BIV red orange yellow green blue indigo violet ordering it is not clear that such an ordering would lead to an intuitive understanding of AMOS Terminal System User s Guide 5 2 Using Color Effectively the structure of the layers As the application increases in complexity the demands for the proper use of color also increase Effective color usage depends upon matching the physiological perceptual and cognitive aspects of the human visual system This chapter will describe some well documented aspects of the human visual system and provide some basic principles that should allow for improved color displays While this may seem like overkill when you simply wish to change the color of text on the screen the principles laid out can help you devise more pleasing and more functional screen displays It is helpful to understand the ways in which colors can
179. ncrease the purity and lightness of the available colors Color hard copy then is produced by the subtractive combination of inks or dyes In most applications the three primaries used are yellow cyan blue green and magenta These three in all possible combinations provide a minimum palette of eight colors as shown in the table below AMOS Terminal System User s Guide Using Color Effectively Page 5 15 Color Subtractive Combination Red Yellow Magenta Green Cyan Yellow Blue Magenta Cyan Yellow Yellow Cyan Cyan Magenta Magenta White Black Yellow Cyan Magenta Pure black is often included as a fourth color simply because the three primaries which produce the best chromatic color usually do not produce the best black To extend the hardcopy palette beyond eight colors requires that different levels of the colors appear in each mixture Two density levels increase the palette to 20 colors An alternative method of increasing the number of available colors is known as half toning This technique places color on the paper as tiny dots that can either vary in frequency or size Pure red for example would require the highest dot frequency available while a desaturated pink would result from halving that frequency In this technique the resulting hue occurs as a result of the additive mixture of red and the white of the paper whereby the dot frequency defines the density of the color component 5 6 2Additive Color M
180. nction by number reserved terminal characteristics terminal driver capabilities word AMOS Terminal System User s Guide Page Index 5 15 46 12 1 14 7 15 21 12 1 14 7 15 49 12 1 15 46 1 3 8 3 15 50 2 2 14 1 15 1 14 5 14 1 14 9 15 35 15 49 2 2 16 1 Page Index 6 AMOS Terminal System User s Guide echo routine 16 2 16 5 emulation oss terit d Ue ne eee awed 16 8 header iu edo p Shanta eed Beet ete 16 1 impure area 16 3 initialization routine 16 2 16 7 input routine eea 16 2 16 4 output routine 16 2 16 5 Structure eats ERAS 16 1 TOR E route 16 2 16 6 TRMCHR routine 16 4 16 7 type DIS scs bein 16 2 terminal independence 1 3 terminals field 3 iuret ie ep Rd 3 1 to 3 2 modes Sos eek Goat Feds std Seed 4s faves us Pavia 3 1 to 3 2 TIME aot Debs tS dios Stab Coil ior a 15 47 Toggle port 15 48 translation tables D 1 transparent print 12 1 14 7 15 22 TRM HR a E exi 2 3 10 2 15 1 16 4 16 7 TRMCHR SBR 2 3 underline eese a 6 1 unlock keyboard 15 3 vertical size codes B 6 Vertical Tab
181. ng things based on physcial position like appearance symmetrical balance and any other hint that there might be structure to the display A cluttered or unclear display requires extra effort to make sense of beyond that of our basic perceptual mechanisms The user who must deal with such a display is forced to take extra time and AMOS Terminal System User s Guide 4 4 Principles of Effective Screen Design effort to learn and understand A user given a display which does not require this extra effort will not have to expend this effort We should therefore capitalize on our perceptual desire for order when organizing screen displays Additionally a user new to the system in question is probably already nervous and easily overwhelmed by the data being presented on the screen Presenting that data in an orderly simple fashion can reduce the user s anxiety about using the new system In looking at displays of information eyeball fixation studies indicate that initially one s eyes usually move to the upper left center of the display and then quickly move in a clockwise direction During and following this movement people are influenced by the balance and weight of the titles graphics and text of the display Significant changes in any of these can influence the pattern and order of eye movement Memory is not one of the great human virtues Short term memory is highly susceptible to interference and its contents are always in dang
182. ns some general guidelines for color usage can be stated They are grouped according to the area of their derivation physiological perceptual or cognitive 5 5 1Physiological Guidelines Avoid the simultaneous display of highly saturated spectrally extreme colors Reds oranges yellows and greens can be viewed together without refocusing but cyan and blues cannot be easily viewed with red To avoid frequent refocusing and subsequent visual fatigue extreme color pairs such as red and blue or yellow and purple should be avoided However desaturating spectrally extreme colors will reduce the need for refocusing Avoid pure blue for text thin lines and small shapes Our visual system is just not set up for detailed sharp short wavelength stimuli However blue does make a good background color and is perceived clearly out of the periphery of our visual field Avoid adjacent colors differing only in the amount of blue Edges that differ only in the amount of blue will appear indistinct Older viewers need higher brightness levels Due to the effects of aging higher brightness levels become necessary to distinguish colors Colors change appearance as ambient light level changes Displays change color under different kinds of ambient light fluorescent incandescent or daylight Appearance also changes as the light level is increased or decreased On the one hand a change occurs because of increased or decreased contrast and on t
183. o understand how we can produce the different colors The process by which inks and dyes are combined whether for a magazine or computer output hardcopy is called subtractive color mixture while the generation of phosphor emmissions follows the process known as additive color mixture 5 6 1Subtractive Color Mixture The perceived color of a surface such as a sheet of paper depends upon the capacity of the surface to reflect some wavelengths and absorb others When a surface is dyed with a particular pigment a new reflectance characteristic is created by the ability of that pigment to reflect some wavelengths and absorb others A surface dyed yellow for example might reflect wavelengths above 570 to 580 nm while absorbing most of the longer and shorter wavelengths Consider another surface dyed cyan blue green such that wavelengths of 440 to 540 nm predominate If we were to mix both pigments and deposit them on a surface the resulting color would be green The mixture of cyan and yellow produces green because the yellow pigment absorbs all of the short wavelengths 500 nm and below and some of the middle band of wavelengths 500 to 550 nm The cyan pigment absorbs all of the long wavelengths 560 nm and above and some of the middle wavelengths 500 to 550 nm Thus the yellow absorbs those wavelengths evoking the sensation of blue while the cyan absorbs those wavelengths evoking yellow Between these two extremes a band of wavelengths
184. of this discussion of television is simply to show that we can choose any representation for color that we wish and leave it up to the terminal driver and the terminal itself to convert it to the representation which the terminal actually uses to physically display the colors 5 7 1The Hue Lightness Saturation Model of Color Without trying to examine all of the possible color models that were considered Alpha Micro has adopted the Hue Lightness Saturation HLS model as its standard for specifying color As with most other color models it uses three components hue lightness and saturation for describing a given color We have described in some detail the three components of the HLS system that allow us to specify colors earlier in this chapter As noted earlier the fourth component brightness is not distinguishable from the lightness component when used with display terminals For this reason we will ignore the brightness component and only deal with hue lightness and saturation To be able to conveniently specify colors we need to have an easy way of defining the value for each of our three components Also it is helpful to have a physical model in mind by which we can picture how the color system works The HLS color system is usually depicted as a pair of cones attached end to end as shown in Figure 5 5 Hue is represented as an angle about the vertical axis ranging from 0 to 360 The angle 0 corresponds to blue T
185. oke function keys are detected and translated When the input routine is called the following registers will be set up D1 Contains the input character A5 Indexes the terminal control block for this terminal The N bit will be set if the character in D1 is possibly in a multi keystroke function key sequence The following registers are available for use by the input routine All others must be saved and restored by the input routine if they are to be modified AO A3 A6 D1 D6 D7 The character is returned to the terminal service system in D1 If a simple substitution is to take place the new character should simply be placed in D1 The input routine signals to the rest of the terminal service system what action is to be taken by setting the condition code flags prior to returning to the terminal service system The following settings are valid Z bitset ignore this character the contents of D1 are ignored V bitset force all eight bits of this character into the buffer regardless of input mode N bitset the character in D1 could be the start of a multi keystroke function key allbitsreset the character in D1 is to be processed normally this is the normal case Because the input routine is called at interrupt level the routine does not have a job context and is restricted as to the monitor calls it can issue Specifically you cannot issue SLEEP TTY or any other call requiring a job context In addition because this rout
186. on is available only if the TD RVA TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 112END REVERSE VIDEO BLINKING TEXT W O A SPACE TCRT 1 111 This call disables the reverse video and blinking text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 35 command but does not occupy a screen position This function is available only if the TD RVA TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals AMOS
187. onship between perceived intensity and physical intensity is nearly logarithmic with perceived intensity increasing as the logarithm of stimulus intensity We have all experienced this relationship when switching brightness of a three way lamp the brightness increase from 50 to 100 watts appears greater than that when switching from 100 to 150 watts AMOS Terminal System User s Guide Using Color Effectively Page 5 7 5 3 2Perception of Achromatic Color White or achromatic light contains all the wavelengths to which the human eye responds When such light strikes an object and all wavelengths are reflected equally the color of the object is achromatic that is the object appears white black or some intermediate level of gray The lightness of the object depends on the amount of light reflected An object reflecting 8096 or more appears very light we would call it white Reflection of 396 or less results in objects appearing very dark black Various levels of gray appear in between with lightness appearing to increase toward white as the logarithm of reflectance Consider for example black white and gray automobiles Each car reflects different amounts of light and therefore takes on a specific achromatic color If the total amount of light falling on the cars is increased the lightness stays the same but the brightness increases The white car stays white but becomes much brighter Thus lightness is a property of the object
188. oth scrolling This function is available only if the TD SMT bit is set in the terminal capabilities flags If a particular terminal does not have different settings for smooth scroll but instead offers only the choice between jump scroll and one speed of smooth scrolling this call will select smooth scrolling 15 99SELECT MEDIUM SLOW SMOOTH SCROLL TCRT 1 98 This call selects the next to slowest of the available smooth scrolling modes See the information on TCRT 1 95 for more information on smooth scrolling This function is available only if the TD SMT bit is set in the terminal capabilities flags If a particular terminal does not have different settings for smooth scroll but instead offers only the choice between jump scroll and one speed of smooth scrolling this call will select smooth scrolling AMOS Terminal System User s Guide Terminal Control Commands Page 15 27 15 100SELECT SLOW SMOOTH SCROLL TCRT 1 99 This call selects the slowest of the available smooth scrolling modes See the information on TCRT 1 95 for more information on smooth scrolling This function is available only if the TD SMT bit is set in the terminal capabilities flags If a particular terminal does not have different settings for smooth scroll but instead offers only the choice between jump scroll and one speed of smooth scrolling this call will select smooth scrolling 15 101START UNDERSCORED AND BLINKING TEXT TCRT 1 100 This call en
189. other to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 105START UNDERSCORED REVERSE VIDEO BLINKING TEXT TCRT 1 104 This call enables the underscore reverse video and blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 AMOS Terminal System User s Guide Terminal Control Commands Page 15 29 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style On color terminals the reverse video attribute reverses the foreground and background colors For example if the currently selected colors are a white foreground on a blue background all reverse video text would be displayed as blue foreground characters on a white background This function is available only if the TD RVA and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is pres
190. ound characters on a white background This function is available only if the TD RVA and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 36END REVERSE VIDEO BLINKING TEXT TCRT 1 35 This call disables both the reverse video and the blinking text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD RVA and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present o
191. ous starting point in the upper left corner of the screen This is where reading starts in most Western cultures and where the eye usually first lands when presented with a screen display AMOS Terminal System User s Guide Principles of Effective Screen Design Page 4 5 Reserve specific areas of the screen for certain kinds of information such as commands error messages and input fields and maintain these areas consistently on all screens People tend to have good location memory so that once they have learned where to look for a specific information item they will tend to look there again Provide cohesive groupings of screen elements by using blank spaces surrounding lines different intensity levels varying display techniques and so on Cohesive groupings allow people to perceive a full screen as having identifiable pieces smaller chunks that may be more easily handled Blank or white space is one way to achieve this Use of contrasting display techniques such as differing intensity levels or reverse video are some other ways Provide symmetrical balance Techniques for achieving balance include centering titles and illustrations in the vertical axis eplacing like elements on both sides of the axis eplacing lighter elements further from the vertical axis and larger elements closer to it Provide only information that is essential to making a decision or performing an action Do not overwhelm a person with information The
192. own in Table B 2 Column one on all status lines contains the status line attribute By reserving this position for the attribute it becomes possible to select the entire status line as having a single attribute For this reason column one on all status lines must not be used to display normal text For example column one of the top status line on an AM 62A terminal normally contains a start underscore attribute resulting in the top status line being underlined If text is written to column one the attribute will be lost resulting in the top status line being displayed as normal text If your program modifies the status line attributes in column one be sure to restore the attribute before your program exits By always restoring the attributes all programs know the status line configuration upon start up 8 3 1Choosing Where to Display Information When choosing how to lay out your screen display it is important to keep in mind some important facts about status lines While the terminal system command set supports both a top status line and a shifted and unshifted bottom status line not all terminals have these capabilities In addition some system software may usurp one of these status lines for its own use AMOS Terminal System User s Guide 8 4 Programming a Status Line Because most modern terminals have at least a single bottom status line the unshifted bottom status line should be where your most important information is
193. p configuration For any of the 16 palette indices you can specify the desired color in terms of its HLS color value For selecting color palette indices based on RGB color specification see TCRT 1 157 To select a color index start by issuing a TCRT 1 177 call For each color index you wish to select output a color index and the desired H Hue L Lightness and S Saturation color values You can repeat this process for as many color indices as you wish End the color selection process by sending a 177 octal 7F hex code The color index is an eight bit value while H L S are 12 bit values All are output using the packing method described in Appendix A of the AM 72 Programmer s Manual The HLS values for the 64 available colors are shown in Appendix G of that manual To reset the color palette to its power up configuration issue a TCRT 1 157 call and immediately follow it with a 176 octal 7E hex code This resets the color palette and terminates the palette selection commands It is best to reset as many palette indices as possible with a single TCRT call in order to eliminate display artifacts such as flashing or unpleasant color combinations 15 176SELECT PC CHARACTER SET TCRT 1 178 VERSION 2 00 AND LATER Primarily used by the VPC Coprocessor for PC Terminal operation this call selects the PC character set instead of the native character set AMOS Terminal System User s Guide 15 48 Terminal Control Commands
194. page In this manner successive use of this call will cause the screen to alternate between the two pages of screen display This function is available only if the TD ALP bit is set in the terminal capabilities flags 15 88COPY TO ALTERNATE PAGE TCRT 1 87 This call copies the contents of the currently displayed screen page to the alternate screen page This is useful when you wish to make minor modifications to the current screen image but wish to be able to present the results all at once via a Toggle Displayed Page command TCRT 1 86 This command can be used to effect limited animation on the terminal screen This function is available only if the TD ALP bit is set in the terminal capabilities flags 15 89INSERT COLUMN TCRT 1 88 This call inserts a single space into all rows in the current screen segment It moves all characters right one position starting from the cursor position to the end of the row A space is placed in the column where the cursor is located The last character on each row is lost This function is available only if the TD KID bit is set in the terminal capabilities flags 15 90DELETE COLUMN TCRT 1 89 This call deletes a character from all rows in the current screen segment All characters starting from the current cursor column to the end of the row are moved one character position to the left A space is placed at the last character position each of the rows This function is available only if the TD KI
195. pendence AMOS Terminal System User s Guide CHAPTER 3 INTRODUCTION TO TERMINALS 3 1 CONVERSATIONAL VS BLOCK MODE Conversational mode is a method of terminal operation where information is sent to and received from the terminal on a character by character basis In conversational mode all editing and display is controlled by the host computer with no intervention by the terminal itself This is the mode in which the Alpha Micro computer and terminals were designed to work This method of operation provides the most flexibility by placing the various editing functions in the host computer This avoids the complications that arise when trying to handle a special editing task for which a terminal was not specifically designed Block mode is a method of handling terminals first used on large mainframe systems as a way of giving the appearance of interactive applications without actually disturbing the underlying batch nature of the large systems Rather than sending individual characters as they are typed as in conversational mode in block mode individual fields and even whole screens are stored up within the terminal and sent as a block This method may have been attractive on some older Systems but it suffers from some severe limitations in an interactive environment Because all editing is performed within the terminal software designers are limited to providing only that editing regardless of the special needs of an application In additio
196. peration itself 13 8VARIABLE SCROLL RATES Video terminals have traditionally used a method of scrolling the screen display known as jump scrolling In this mode each line simply disappears off the top of the screen to be replaced with the new line Newer terminals have implemented a method of scrolling known as smooth scrolling where the text of the line is rolled off the top of the screen one character dot at a time Smooth scrolling is generally considered to be more visually pleasing than jump scrolling but restricts the rate at which information can be scrolled on the screen Therefore it is usually used under special circumstances rather than as the normal mode of operation Terminal command calls TCRT 1 96 through TCRT 1 99 are provided for up to four different smooth scrolling rates although not all terminals provide all of these different scroll rates The TCRT 1 95 command selects jump scrolling The smooth scrolling commands are available only if the TD SMT bit is set in the terminal capabilities flags AMOS Terminal System User s Guide PART IV THE TCRT COMMAND CODES AMOS Terminal System User s Guide 14 AMOS MONITOR TCRT CODES 14 1INDEX TO QUICK REFERENCE This chapter provides two quick references to the available TCRT commands one is arranged by TCRT command number and the other is arranged by function More detailed information on each command can be found in Chapter 15 14 1 1
197. port this call nothing is output AMOS Terminal System User s Guide 15 46 Terminal Control Commands 15 1650UTPUT PLUS OR MINUS CHARACTER TCRT 1 167 This call outputs a plus or minus character at the current screen location If the terminal driver does not support this call nothing is output 15 1660UTPUT GREATER THAN OR EQUAL CHARACTER TCRT 1 168 This call outputs a greater than or equal character at the current screen location If the terminal driver does not support this call nothing is output 15 1670UTPUT LESS THAN OR EQUAL CHARACTER TCRT 1 169 This call outputs a less than or equal character at the current screen location If the terminal driver does not support this call nothing is output 15 1680UTPUT NOT EQUAL CHARACTER TCRT 1 170 This call outputs a not equal character at the current screen location If the terminal driver does not support this call nothing is output 15 1690UTPUT BRITISH POUND CHARACTER TCRT 1 171 This call outputs a British pound character at the current screen location If the terminal driver does not support this call nothing is output 15 1700UTPUT PI CHARACTER TCRT 1 172 This call outputs a pi character at the current screen location If the terminal driver does not support this call nothing is output 15 171ENTER BIDIRECTIONAL PRINT MODE TCRT 1 173 This call enables the bidirectional concurrent print function Upon issuance of this call the terminal sends all subseq
198. pport this function this call is simply ignored 15 30MAKE CURSOR INVISIBLE TCRT 1 29 This call turns off the cursor and makes it invisible It is used in conjunction with the TCRT 1 28 call above to hide the cursor during screen update This produces a more pleasant screen display than one where the cursor is flashing around on the screen If a particular terminal does not support this function this call is simply ignored 15 31START UNDERSCORED TEXT TCRT 1 30 This call enables the underscore text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD UND bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure the text is properly aligned even if the attribute is not
199. present in any form 15 32END UNDERSCORED TCRT 1 31 This call disables the underscore text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TD UND bit is set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form AMOS Terminal System User s Guide Terminal Control Commands Page 15 9 15 33START REVERSE VIDEO TEXT TCRT 1 32 This call enables the reverse video text attribute As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3
200. r not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form 15 37TURN OFF SCREEN DISPLAY TCRT 1 36 This call blanks the terminal screen until a TCRT 1 37 function is executed This call is useful for temporarily hiding the screen from the operator during screen update This can result in a more pleasing display If a particular terminal does not have this function this call will simply be ignored 15 38TURN ON SCREEN DISPLAY TCRT 1 37 This call unblanks the terminal screen reversing the effect of the TCRT 1 36 call These two functions are useful for temporarily hiding the screen from the operator during screen update This can result in a more pleasing display If a particular terminal does not have this function this call will simply be ignored AMOS Terminal System User s Guide Terminal Control Commands Page 15 11 15 39TOP LEFT CORNER CHARACTER TCRT 1 38 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one scr
201. racters that the code is to be translated to When a function key is pressed indicated by the high order bit being set the application program simply scans the table for the function key value received and then uses the string of characters as its input By convention all function key translation tables have a file extension ending in X Some common translation table extensions are AMX General purpose table AIphaCALC translation table FIX AlphaFIX translation table MAX AlphaMAIL translation table MULTI translation table VUX AIphaVUE translation table WRX AIDhaWRITE translation table The internal format of these tables as well as other function key translation tables used by AMOS is described in Appendix D 9 2 1Loading a Function Key Translation Table Your program should select the translation table to be used based on the name of the terminal driver in use This can be located by first locating the job s terminal definition block pointed to by JOBTRM within the job s JCB then locating the terminal driver pointed to by T TDV within the terminal definition block The terminal driver name is stored in the four bytes immediately preceding the terminal driver itself packed RAD5O For example the following code will load the filename field of a DDB indexed by A4 with the name of the terminal driver in use It then loads the DDB extension field with an extension of AMX and fetches the translation ta
202. raints of the terminal being used and the software which is driving it A well designed screen will be consistent within itself within related screen formats and with other screens in the same system AMOS Terminal System User s Guide Principles of Effective Screen Design Page 4 3 4 ATHE HUMAN CONSIDERATIONS Computers are only of use when they can be used by humans We have not yet reached the point where computers are truly used by other computers without humans in the chain some where The fact that humans are involved is both a blessing and a curse A blessing because there are certain behavior patterns we know and can take advantage of and because if all else fails that person is capable of rational thought to determine what action is needed next A curse because people are picky hard to please difficult to deal with and demanding We need to understand both sides of people in order to develop effective screens One large insurance company s MIS department asked their users what they looked for in a good screen design and they listed the following eOrderly clean clutter free appearance eObvious indication of what is being shown and what should be done with it eExpected information where it should be eClear indication of what relates to what headings field captions etc ePlain simple English eA simple way of finding out what is the system and how to get it out eA clear indication of when an action could make
203. ram sends the Exit Transparent Print Mode call TCRT 1 83 to return the terminal to the normal conversational mode of operation As with the Screen Print function some characteristics of this function are undefined as they depend on the particular combination of terminal and printer in use In particular input from the keyboard may or may not be acted on In addition any XON XOFF protocol used by the printer may or may not be returned to the host Like Screen Print attention must be paid to the error recovery aspects of using the Transparent Print mode AMOS Terminal System User s Guide 13 MISCELLANEOUS FEATURES This chapter descibes a series of commands that perform special display functions on the terminal screen Typically they do not do anything that could not be accomplished by using the simpler screen commands or by simply repainting the screen instead what they offer is better performance by reducing the time to update the screen display or a more pleasing appearance for the user 13 1BLOCK FILL There are times when it is desirable to fill a rectangular area of the screen with a repeating character Most commonly the space character can be used to clear a rectangular region of the screen This is often used for removing menus from the screen Two terminal commands allow you to fill a rectangular area of the screen with a specific character or attribute To fill an area of the screen with a character
204. rd orange Conversely increasing the intensity of the green would move the color towards yellow green AMOS Terminal System User s Guide 5 16 Using Color Effectively All three phosphors together produce a very broad distribution of wavelengths which evokes the sensation of white Varying the intensity or gray level of the three phosphors produces different levels of lightness Because one is able to mix most hues as well as achromatic colors by additively combining red green and blue these are called the primary colors of additive color mixture By selectively combining the red green and blue phosphors we can produce eight colors just as we did with the subtractive primaries Color Additive Combination Red Red Green Green Blue Blue Yellow Red Green Cyan Green Blue Magenta Red Blue White Red Blue Green Black If we can control the relative intensities of the three phosphors we can create a much larger palette of colors If we can select among four different intensities including off for each phosphor we get a palette of 64 colors Encoding such a palette would require two bits per phosphor or a total of six bits Additional control over each phosphor gets us larger and larger color palettes The largest color palette commonly used with color display terminals allows 8 bits per phosphor allowing for a selection of 256 different intensities for each of the three phosphors This yields a palette
205. rectional print mode Set terminal time set terminal date select color palette by HLS value select PC character set select default character set select PC terminal emulation select ASCII terminal operation select AUX port host select main port host select toggle host ports select 8 bit character display select 7 bit character display select 8 bit keyboard mode select 7 bit keyboard mode select primary printer port select secondary printer port select 161 column display mode AMOS Terminal System User s Guide AMOS Monitor TCRT Codes TCRT 1 192 thru 255 TCRT 2 n TCRT 3 n TCRT 4 n thru 5 n 14 1 2TCRT Codes by Function Page 14 5 RESERVED select foreground color n select background color n RESERVED 14 1 2 1Cursor Positioning Commands TCRT 1 1 TCRT 1 2 TCRT 1 3 TCRT 1 4 TCRT 1 5 TCRT 1 6 14 1 2 2Screen Clearing Commands TCRT 1 0 TCRT 1 9 TCRT 1 10 14 1 2 3Display Attribute Commands TCRT 1 11 TCRT 1 12 TCRT 1 21 TCRT 1 22 TCRT 1 27 TCRT 1 30 TCRT 1 31 TCRT 1 32 TCRT 1 33 TCRT 1 34 TCRT 1 35 TCRT 1 100 TCRT 1 101 TCRT 1 102 TCRT 1 103 TCRT 1 104 TCRT 1 105 TCRT 1 106 TCRT 1 107 TCRT 1 108 TCRT 1 109 AMOS Terminal System User s Guide cursor home move to column 1 1 cursor return move to column 1 cursor up cursor down cursor left cursor right clear screen erase to end of line erase to end of screen
206. red inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 132SELECT BLUE TEXT TCRT 1 134 This command selects the current text color to be blue on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 133SELECT MAGENTA TEXT TCRT 1 135 This command selects the current text color to be magenta on the standard background This function occupies one screen position and is therefore considered inferior to the general color selection commands TCRT 2 n and TCRT 3 n It is provided for compatibility with certain terminals such as the AM 70 only and is not recommended for use in new software development This function is available only if the TD CLR and TD PHR bits are set in the terminal capabilities flags 15 134SELECT RED TEXT TCRT 1 136 This command selects the current text color to be red on the stan
207. riting text to the screen For this reason it is important the applications software not make any assumptions regarding the interaction of protected text with any command other than the three erase screen commands TCRT 1 0 1 9 and 1 10 lest the program become terminal dependent AMOS Terminal System User s Guide CHAPTER 8 PROGRAMMING A STATUS LINE Most modern terminals now have one or more status lines which can be displayed on the screen in addition to the normal text This chapter will describe what these status lines are and how to use them in a terminal independent fashion 8 1INTRODUCTION TO STATUS LINES Status lines provide the programmer with one or more non scrolling rows of text in addition to the normal text display Because they are non scrolling they are often used for displaying fixed status information that should not be disturbed during normal program execution Typical uses would be the name of the program being run the file being edited or the current operating mode of the program When status lines first became available they were often referred to as the 25th line because of their position on the screen following the standard display of 24 rows of text This 25th line often displayed the current operating mode of the terminal displaying such items as whether the terminal was on or off line what the state of the DTR control line was etc In addition some terminals also had a small portion of the s
208. rminal driver For these reasons any use of this command increases terminal dependence and is therefore not recommended AMOS Terminal System User s Guide Terminal Control Commands Page 15 17 15 61SET VERTICAL SPLIT DIVIDER CHARACTER TCRT 1 60 This command when followed by a single character places a vertical column of that character down the center of the screen in column 40 This command is used to display a screen divider character when using vertical split screen mode This function is available only if the TD SPL bit is set in the terminal capabilities flags NOTE Very few terminals support the use of a vertical split screen and because of the complexity of the operation it is very unlikely that the operation will be supported via software emulation within the terminal driver For these reasons any use of this command increases terminal dependence and is therefore not recommended 15 62ACTIVATE SCREEN SEGMENT 0 TCRT 1 61 This command selects screen segment 0 the upper part for horizontal split the left part for vertical split as the place to receive all subsequent commands and text Segment 0 will remain the active segment until an Activate Screen Segment 1 command TCRT 1 62 command is given This command is only valid after a split screen command TCRT 1 57 1 58 or 1 59 has been given It is ignored if the terminal screen is not currently split This function is available only if the TD SPL bit is set in
209. rminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 22 command but does not occupy a screen position This function is available only if the TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 121SET CURSOR TO BLINKING BLOCK TCRT 1 120 This command sets the text cursor shape to be that of a blinking block On terminals which do not support changing the cursor shape this command will be ignored AMOS Terminal System User s Guide Terminal Control Commands Page 15 35 15 122SET CURSOR TO STEADY BLOCK TCRT 1 121 This command sets the text cursor shape to be that of a steady non blinking block On terminals which do not support changing the cursor shape this command will be ignored 15 123SET CURSOR TO BLINKING UNDERLINE TCRT 1 122 This command sets the text cursor shape to be that of a blinking underline On terminals which do not support changing the cursor shape this command will be ignored 15 124SET C
210. rnate page commands are available only if the TD ALP bit is set in the terminal capabilities word 13 4CURSOR SHAPE CONTROL The shape of the cursor is often a matter of personal choice for the user of the terminal Typically the cursor shape can be chosen from several different possibilities via switches on the terminal or through a terminal set up procedure There are times however when it is useful to be able to select the shape of the cursor via software control For this reason four terminal commands TCRT 1 120 through 1 123 allow you to select the cursor shape In addition to controlling the shape of the cursor commands are also available to turn the cursor on and off When updating the screen turning the cursor off during the update can make the operation much more pleasing to the eye by eliminating any ghosting of the cursor on the screen Use TCRT 1 29 to turn the cursor off and TCRT 1 28 to turn it back on If a particular terminal does not support one or more of these commands the command will simply be ignored 13 5VIDEO ENABLE DISABLE In addition to turning the cursor off while updating the screen some terminals allow you to turn off the video display during updates further reducing the visual clutter of updating the screen When the entire screen is to be repainted you can disable the video blanking the screen display by using a TCRT 1 36 command Once the update is complete turn the screen displ
211. rograms should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 1198 TART BLINKING TEXT W O A SPACE TCRT 1 118 This call enables the blinking text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 21 function but does not occupy a screen position This function is available only if the TD BLK and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 120END BLINKING TEXT W O A SPACE TCRT 1 119 This call disables the blinking text attribute without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented te
212. rove difficult to distinguish for certain classes of color deficient observers 5 5 2Perceptual Guidelines Not all colors are equally discernible Perceptually we need a large change in wavelength to perceive a color difference in some portions of the spectrum and a small one in other portions Luminance does not equal brightness Two equal luminance but different hue colors will probably appear to have different brightnesses The deviations are most extreme for colors towards the ends of the spectrum red magenta blue Different hues have inherently different saturation levels Yellow in particular always appears to be less saturated than other hues Lightness and brightness are distinguishable on a printed copy but not on a color display The nature of a color display does not allow lightness and brightness to be varied independently Not all colors are equally readable or legible Extreme care should be exercised with text color relative to background colors Besides a loss of hue with reduced size inadequate contrast frequently results when background and text colors are similar AMOS Terminal System User s Guide Using Color Effectively Page 5 13 Hues change with intensity and background color When grouping elements on the basis of color be sure that backgrounds or nearby colors do not change the hue in an element in the group Limiting the number of colors and making sure they are widely separated in the spectrum will re
213. rs typically just the alphabet numbers and limited punctuation and in character size and style usually a single size and style AMOS Terminal System User s Guide Principles of Effective Screen Design Page 4 7 Terminals do offer several ways of distinguishing text such as reduced intensity reverse video blinking and underlining However each of these has its drawbacks Use of these methods in designing a screen requires that we understand not only how they work the subject of later chapters in this book but also how they are perceived by the people viewing the screen display 4 5 1Blinking Text Blinking text has excellent attention getting ability This is both a benefit and a liability In situations where it is important to capture the operator s attention blinking excels However blinking reduces the legibility of the message you get to see it for less time since it keeps turning itself off and can be quite distracting if it is left on the screen once attention has been gained For this reason it should be limited to situations which require an immediate response and not just used for informational purposes One interesting method of dealing with these problems is to turn off the blinking once the appropriate action has been taken even if the text is otherwise left on the screen 4 5 2Different Brightness Changing the intensity of the characters has good attention getting capability and is the least visually distur
214. s available only if the TD LID bit is set in the terminal capabilities flags AMOS Terminal System User s Guide Terminal Control Commands Page 15 5 15 18DELETE CHARACTER TCRT 1 17 This call deletes the character at the current cursor position All characters starting from the cursor position to the end of the row are moved one character position to the left A space is placed at the last character position in the row If protect mode is on this operation halts at the end of a protected field or the end of the row whichever is encountered first This function is available only if the TD CID bit is set in the terminal capabilities flags 15 19INSERT CHARACTER TCRT 1 18 This call inserts a single space into the row the cursor is positioned on It moves all characters right one position starting from the cursor position to the end of the row A space is placed at the cursor position The last character on the row is lost If protect mode is on this operation halts at the end of an unprotected field or the end of the row whichever is encountered first This function is available only if the TD CID bit is set in the terminal capabilities flags 15 20READ CURSOR ADDRESS TCRT 1 19 This call allows a program to query a terminal as to its current cursor position After issuing this call the program must wait for the terminal to respond with the cursor row and column address The address is encoded as described in Table B 1 and
215. ssion especially to terminals The code includes 128 upper and lower case letters numerals and special purpose symbols each encoded by a unique 7 bit binary number attribute A particular display enhancement that can be applied to any character displayed on a terminal Typical enhancements include underscoring reverse video dimmed video and blinking baud rate Synonymous with signal events bits per second and used as a measure of serial data flow between a computer and or communications devices character attribute A display enhancement that applies to individual characters If the character is replaced with another the attribute is not preserved A character attribute is independent of terminal screen location but is instead associated with the character itself control character A character whose occurance in a particular context initiates modifies or halts operation Control codes are assigned ASCII character codes below the space character cursor A small moving indicator on a CRT terminal which indicates the position where the next character will be output The cursor can be displayed in a variety of shapes including small rectangular blocks or an underline It may blink or not or may be turned off entirely field attribute A display enhancement that applies to a particular area of the terminal screen in particular the area before begin attribute and end attribute markers full duplex Refers to a communica
216. st add to be able to perceive the color we can see that different hues saturate at different points For example a yellow at 570 nm requires that largest amount of pure hue to be perceived Such a yellow appears initially to be less saturated than any other pure hue and desaturates quickly as the distribution is broadened or as neutral colors are mixed with it Lightness as mentioned previously refers to those achromatic colors ranging from white through gray to black By definition achromatic colors are completely desaturated since no trace of hue is present Just as with achromatic colors the lightness of a mixed color also depends on the reflectance of the surface under consideration the higher the reflectance the lighter the color As might be anticipated monochromatic colors do not all appear equal in lightness Some hues appear lighter than others even though their reflectances are the same If for example observers are shown a series of monochromatic lights of equal brightness and are asked to rate them for lightness we will see variations across the range of wavelengths A monochromatic color at 570 nm yellow appears much lighter than all other wavelengths even though the actual brightness is the same Brightness is another aspect of color perception Increasing the illumination of both achromatic and chromatic colors produces a qualitative change in appearance that ranges from dark to bright However separation of brightness
217. t then you may also use the TCRT 1 106 and TCRT 1 107 commands to enable and disable underlining without occupying a screen position 6 3BLINK Text written with the blink attribute is displayed as blinking or flashing text The blink rate is determined by the terminal itself Blink mode is selected by the TCRT 1 21 command and disabled with the TCRT 1 22 command AMOS Terminal System User s Guide 6 2 Screen Display Attributes The screen position occupied by the begin attribute command is displayed as a normal space with no attributes The blinking does not take affect until the next character Likewise the end blinking command is displayed as a normal space with no blinking For the blinking attribute this affect is usually visible only on color terminals If your terminal supports hidden attributes the T NSP bit in the TRMCHR characteristics word is set then you may also use the TCRT 1 118 and TCRT 1 119 commands to enable and disable blinking without occupying a screen position 6 4REVERSE Text written with the reverse video attribute is displayed with the foreground and background colors reversed On monochrome terminals in which the normal display mode is light characters on a dark background this will mean that reverse video is dark characters on a light background On color terminals the foreground and background colors are simply exchanged Note that the reverse video attribute is not additive Tha
218. t Gua alan Ete de aii 6 1 6 3 BLINK ue wee oes a LES AE Ro EISE RE LIRE Gains 6 1 6 4 REVERSE ed REM A DUREE 6 2 6 5 COMBINATIONS ei tu Rr REPE ERIT EE 6 2 CHAPTER 7 PROTECTED FIELDS 7 1 THE PROTECTED FIELD COMMANDS 7 2 7 1 1 Enabling and Disabling Protected Fields 7 2 7 1 2 Selecting Text as Protected 7 2 7 2 USING PROTECTED FIELDS ussussssssssele seh 7 2 CHAPTER 8 PROGRAMMING A STATUS LINE 8 1 INTRODUCTION TO STATUS LINES 8 1 8 1 1 The Three Status Lines ossis rea m RR 8 1 8 1 2 Status Line Addressability 8 2 8 2 USING STATUS LINES r arr i SEA E RTE OEE 8 2 8 2 1 Displaying Text a Status Line 8 2 8 3 STATUS EINE ATTRIBUTES o arreen TT 8 3 AMOS Terminal System User s Guide AMOS Terminal System User s Guide Page v 8 3 1 Choosing Where to Display Information 8 3 8 4 STATUS LINE EMULATION ore RR RII I Hu 8 4 CHAPTER 9 USING PROGRAMMED FUNCTION KEYS 9 1 GENERAL CONCEPTS pei adi ed eee VE E O 9 1 9 2 FUNCTION KEY TRANSLATION TABLES 9 1 9 2 1 Loading a Function Key Translation Table
219. t a slight increase in the amount of time required to perform the translation The format of a SET PFK type translation table is as follows Bytes 0 1 Two bytes containing the octal value 121212 which flag this as a valid translation table Bytes 2 nnnnn A series of entries consisting of a single byte containing a function key to be translated followed by a null terminated series of bytes to which the function key is to be translated Byte 1 A zero byte used to terminate the whole file The sequence of events used to translate a function key is as follows 1Start by indexing the table at byte 2 just past the flag word 2lf the byte being indexed contains a zero you have reached the end of the table and there is no translation defined for this function key 3Jf the byte being indexed contains the function key you wish to translate proceed to step 5 4Scan forward in the file until a zero byte is seen Index the byte following the zero and return to step 2 5 You are now indexing a null terminated string containing the characters to which the function key is to be translated Any character except null can be translated via a SET PFK type function key translation table not just those commonly referred to as function keys AMOS Terminal System User s Guide APPENDIX E GLOSSARY ASCII code The acronym for American Standard Code for Information Interchange This standardized code is used extensively in data transmi
220. t available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 78COPYRIGHT CHARACTER TCRT 1 77 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 79REGISTERED CHARACTER TCRT 1 78 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 80P
221. t cannot be practically emulated but affect the operation of the software if they are not present To handle this situation it becomes important for software to be able to detect the presence or absence of a feature in the terminal it is currently being run on The software can then tailor its operation based on the presence or absence of a given feature For this reason a method is provided for determining not only a list of the features supported by the terminal but also other characteristics of the terminal such as the number of rows and columns on the screen and the current color selections For these methods to work note that it is the responsibility of the software to check for the presence of a feature before it attempts to use it If a given feature is marked as absent the results of using that feature are unpredictable Note however that because of our concept of levels of terminals it is not necessary for the software to be constantly checking each and every feature unless it is desired that the software be able to be run on earlier level terminals 1 5RELATED DOCUMENTATION While this book is intended to be largely self contained the following documents may also prove to be useful e introduction to AMOS e AMOS Monitor Calls Manual e AlphaBASIC User s Manual In addition when writing a terminal driver for a particular terminal you will need a copy of the programming manual for that terminal available from the terminal man
222. t generate an octal 301 code while on some other terminal it might generate an octal 205 Thus the applications program must translate from this unique code to the code desired by the program based on the type of terminal being used 9 2FUNCTION KEY TRANSLATION TABLES Because the function key codes returned by the terminal service system differ from terminal to terminal a special translation table is required to convert the unique code output by a particular terminal to the character or characters that the program is looking for This translation table is unique for each particular type of terminal that is to be supported AMOS Terminal System User s Guide 9 2 Using Programmed Function Keys For example the AlphaWRITE and AlphaVUE programs use translation tables that are fetched from the disk each time the program is invoked The choice of which translation table to use is based on the name of the terminal driver in use To locate the function key translation table to use the program simply looks up the name of the terminal driver in use adds on a unique file extension and loads that file into memory For example the translation tables for AlphaVUE all have the extension and are stored in DSKO 7 0 Thus if you are using an AM 60 terminal driver AM60 TDV AlphaVUE will use the translation table named AM60 VUX These translation tables consist of the unique code received from the function key followed by the string of cha
223. t is setting reverse video mode once will reverse the foreground and background colors but issuing it again will not reverse them again The only way to return to normal video is to issue an end reverse video command Reverse video mode is selected by the TCRT 1 32 command and disabled with the TCRT 1 33 command The screen position occupied by the begin attribute command is displayed as a normal space with no attributes The reverse video does not take affect until the next character Likewise the end reverse command is displayed as a normal space with no reverse video If your terminal supports hidden attributes the T NSP bit in the TRMCHR characteristics word is set then you may also use the TCRT 1 108 and TCRT 1 109 commands to enable and disable reverse video without occupying a screen position 6 5COMBINATIONS In addition to the pure use of the attributes described above the attributes can be combined to create many other combinations The dim video attribute can be combined with any other attribute by issuing both the begin dim and begin attribute commands where attribute is one of the other terminal attributes The effects of these two commands are additive For combining the other attributes reverse blinking and underscored there are special terminal system commands defined to allow all of the possible permutations Any of these permutations may be combined with the dim attribute The screen posit
224. t up A5 Indexes the terminal control block for this terminal The following registers are available for use by the initialization routine All others must be saved and restored by the routine if they are to be modified A6 D1 D3 D6 At the time that the initialization routine is called the terminal is not attached to a job thus preventing the use of normal terminal output calls such as TTY TTYL or TTYI Any such output will appear on the booting terminal rather than on the terminal being initialized To output to the terminal being initialized use the TRMBFQ monitor call Remember that all output from the this routine eventually ends up going out through the terminal driver output routine Because the initialization routines of all terminals on the system are called in rapid succession during system bootup care must be taken in this routine to not run the system out of queue blocks since no extra queue blocks may have been allocated at this point in the boot process For this reason it is a good idea to test the system longword QFREE and skip over the initialization process if it contains a value less than 15 decimal 16 1 7The Terminal Driver TRMCHR Routine The TRMCHR routine of the terminal driver is called whenever the job attached to the terminal issues a TRMCHR monitor call It is the responsibility of the TRMCHR routine to fill in the user s argument block with the current settings and values describing the terminal Wh
225. tatus line available for the display of arbitrary text by the host computer Because the terminal status information was mainly of use only to block mode users terminals soon appeared with the entire 25th line dedicated to programmable display thus finally becoming useful to interactive users 8 1 1The Three Status Lines Once the programmable 25th line became popular some terminal manufacturers started to include more than one status line on the screen thus obsoleting the term 25th line Our standard terminal interface supports up to three status lines The first referred to as the bottom status line or function key labeling line appears at the bottom of the screen in the same position as the old style 25th line Most modern terminals have this capability In addition a shifted bottom status line or shifted function key labeling line is supported This line also appears at the bottom of the screen but is visible only when the SHIFT key on the keyboard is pressed This function is not available on all terminals but is supported for terminals which have this capability AMOS Terminal System User s Guide 8 2 Programming a Status Line A third status line often referred to as the top status line or host message field is also supported This status line appears at the top of the screen above the normal text display area This function is not available on all terminals but is supported for terminals which hav
226. terminals i e number of colors is greater than zero the minimum number of available colors will be eight The argument values for the first eight colors can be found in Table B 3 This call does not occupy a screen position AMOS Terminal System User s Guide 15 50 Terminal Control Commands This function is available only if the TD CLR bit is set in the terminal capabilities flags 15 192SET BACKGROUND COLOR TCRT 3 N This call selects the background color to be used for all further text display The call takes an eight bit argument n which specifies the color to be selected The range of values for this argument can be obtained via the TRMCHR monitor call or the TRMCHR XCALL routine from AIphaBASIC t is assumed that for all color terminals i e number of colors is greater than zero the minimum number of available colors will be eight The argument values for the first eight colors can be found in Table B 3 This call does not occupy a screen position This function is available only if the TD CLR bit is set in the terminal capabilities flags 15 193RESERVED FUNCTIONS TCRT 4 N THROUGH TCRT 127 N These functions are reserved for future expansion by Alpha Micro If you have a specific need for a new TCRT function you may contact Alpha Micro to reserve a TCRT call number The reservation process avoids problems arising from incompatable extensions to the TCRT functions AMOS Terminal System User s Guide
227. the TCRT 1 61 and TCRT 1 62 calls The cursor will only appear in the currently selected segment The cursor position is remembered for both segments Thus positioning the cursor in one segment then selecting the other will cause the displayed cursor to change positions on the screen However once the original segment is once again selected the cursor will move back to its original position within that segment To remove the split screen use the TCRT 1 56 call to reset the terminal to its original state The split screen commands are only available if the TD SPL bit is set in the terminal capabilities word 13 3ALTERNATE PAGE Some terminals offer a feature known as an alternate page Normally your terminal screen displays what is known among terminal manufacturers as a page of memory By installing additional memory inside the terminal the terminal can contain another page in addition to the one being displayed on the terminal screen The advantage of this feature is that the terminal is capable of switching the screen display from one page to the other very quickly This can provide the appearance of a screen update far in excess of the speed with which it can be updated by clearing and repainting it By sending text to the alternate page via the TCRT 1 84 call you can create an entire screen display without altering the one currently being displayed By selecting the alternate page all commands and text you send to
228. the TCRT routine are not immediately sent to the terminal but are buffered along with all other output characters These characters will eventually be passed through the terminal driver output routine and on to the terminal This delay in the processing of output characters can be important when emulating certain features which must process both TCRT calls and subsequent output characters If a TCRT call requires following address characters such as addressable status lines or the box and area fill commands the following address characters will need to be pulled from the output stream within the terminal driver output routine AMOS Terminal System User s Guide PART VI REFERENCE MATERIALS AMOS Terminal System User s Guide APPENDIX A ASCII CHARACTER CHART The next few pages contain a chart listing the complete ASCII character set We provide the octal decimal and hexadecimal representations of the ASCII values Note that the first 32 characters are non printing control characters THE CONTROL CHARACTERS CHARACTER OCTAL DECIMAL HEX MEANING NULL 000 0 00 Null fill character SOH 001 1 01 Start of Heading STX 002 2 02 Start of Text ETX 003 3 03 End of Text ECT 004 4 04 End of Transmission ENQ 005 5 05 Enquery ACK 006 6 06 Acknowledge BEL 007 7 07 Bell code BS 010 8 08 Back Space HT 011 9 09 Horizontal Tab LF 012 10 0A Line Feed VT 013 11 0B Vertical Tab FF 014 12 0C Form Feed CR 015 13 00 Carriage Return SO 016 14
229. the center of the retina while capable of high acuity has almost no cones with the blue photopigment The result is a blue blindness that causes small blue objects to disappear when they are fixated upon in the center of our field of vision For the eye to detect any shape of a specific color an edge must be created by focusing the image onto the mosaic of rods and cones An edge is a basic element in perceiving form It can be created by adjacent areas differing in brightness color or both Edges guide the eye s accomodation mechanism which brings images into focus on the retina Recent research has shown however that edges formed by color difference alone with no brightness difference such as a red circle centered on a large green square of equal brightness are poor guides for accurate focusing Such contours remain fuzzy For sharply focused images itis necessary to combine both brightness and color differences AMOS Terminal System User s Guide Using Color Effectively Page 5 5 Also for photopigments to respond a minimum level of light is required This accounts for the fading of colors as the sun sets As the light level decreases the cones eventually stop contributing to vision shifting the burden entirely to the photopigmentless rods Additionally the response level of the photopigments depends on wavelength with greatest sensitivity at the center of the spectrum with decreasing sensitivity at the spectral extremes This me
230. the terminal will not be displayed but instead will only affect the as yet invisible alternate page of memory After exiting this alternate page mode via the TCRT 1 85 call you can quickly change to displaying the alternate page by issuing a TCRT 1 86 call When you select the alternate page it becomes the current page and the previously displayed page becomes the alternate page Thus the TCRT 1 86 command simply toggles between the two pages with the one being displayed being the current page and the one that is not being displayed being the alternate page By repeatedly sending this TCRT 1 86 call you can switch rapidly back and forth between the two displays AMOS Terminal System User s Guide Miscellaneous Features Page 13 3 Typical uses for the alternate page include storing a help screen in the alternate page to make additional information available to the user very quickly Additionally by rapidly switching between pages limited animation effects can be realized Since successive screen displays are often only slight modifications of the previous one another helpful command is available on some terminals This command creates a copy of the currently displayed screen in the alternate page of terminal memory By being able to quickly make a copy then having to send only the updates you can reduce the screen update time by avoiding having to send the entire screen image again to update the alternate page The alte
231. the various code sequences needed for each of the terminals This approach has been more successful than the first but simply delays the same result as the first 1 2 3Many Terminals One Code What would seem to be an excellent solution is the idea of creating many different terminals which all accept the same code sequences This has been accomplished through the establishment of the ANSI X3 64 terminal command standard As a national standard it has attracted many different terminal vendors that all produce terminals conforming to this code It would therefore seem to be a simple matter for a software package to simply use only these code sequences and still have a wide variety of terminals to choose from However while ostensibly designed to allow software to have access to many different terminals because it was being promulgated by terminal manufacturers the standard was actually intended to increase the sales for terminals by allowing the sale of terminals to many different partly incompatible computer systems Because many of the computer systems being produced have very restrictive rules about what can and cannot be sent to a terminal the ANSI standard had to specify commands that could be sent from any computer system It therefore resulted in an extremely inefficient set of commands so inefficient in fact that most of the terminal manufacturers that were AMOS Terminal System User s Guide Introduction Page 1 3 pushing h
232. this terminal The following registers are available for use by the TCRT routine All others must be saved and restored by the routine if they are to be modified AO 01 D6 D7 The TCRT routine returns whether or not the operation was successful by returning the Z bit to the user If the operation was successful set the Z bit before returning to the terminal service system If the operation was not successful reset the Z bit You can output characters from within the TCRT routine via the standard terminal output calls such as TTY TTYL TTYI etc While the SLEEP call may be used it is not usually effective as a method of introducting delays since characters are buffered and therefore output at the full baud rate regardless of what the outputting job is doing The standard method of introducing delays is output a sequence of null bytes which are ignored by most terminals Remember that all output from the TCRT routine eventually ends up going out through the terminal driver output routine AMOS Terminal System User s Guide Assembly Language Terminal Drivers Page 16 7 16 1 6The Terminal Driver Initialization Routine The initialization routine of the terminal driver is called when the terminal is first defined at System initialization time Its purpose is to set the terminal into a known state so that the remainder of the system boot process may continue When the initialization routine is called the following registers will be se
233. tion is available only if the TD PRT bit is set in the terminal capabilities flags 15 85BEGIN WRITING TO ALTERNATE PAGE TCRT 1 84 This call causes all further data and commands to affect only the alternate page of memory in the terminal not the current display The data and commands you issue will not be visble until you select the alternate page of memory for display via a TCRT 1 86 call Data and commands will continue to be sent to the alternate page until you issue a TCRT 1 85 call to resume writing to the currently displayed page AMOS Terminal System User s Guide Terminal Control Commands Page 15 23 This command is often used for maintaining two separate screen displays with the ability to very quickly alternate between the displays A typical application would be the display of an application menu and explanatory text with the operator able to quickly flip from one to the other This function is available only if the TD ALP bit is set in the terminal capabilities flags 15 86END WRITING TO ALTERNATE PAGE TCRT 1 85 This call cancels the effect of the TCRT 1 84 call and resumes the direction of all commands and data to the current screen display This function is available only if the TD ALP bit is set in the terminal capabilities flags 15 87TOGGLE DISPLAYED PAGE TCRT 1 86 This call selects the alternate screen page for display and causes the page being displayed at the time of the call to become the alternate
234. tion keys status lines split screen and video on off The subsequent introductions of the AM 62 AM 62A and Workstation terminals have introduced additional features such as switchable 80 132 column modes color and printer ports AMOS Terminal System User s Guide Introduction Page 1 5 Note that because the feature set is getting richer over time software written for an earlier set of features continues to function if not quite as efficiently as it might if written with the latest features 1 4 2Dealing with Feature Differences While a standard interface is provided to give software access to all of the possible features that a terminal might have we still must deal with terminals that do not have all of those features Three methods are used to deal with this The first is emulation of the feature On many terminals it is possible to emulate the operation of a particular feature by combining several other features This is the first choice whenever a feature is missing from a terminal as it preserves the most functionality Because it is not always practical to emulate a particular feature we must sometimes use our second method which is to simply ignore the command This is particularly successful with features that may improve the appearence of the screen display such as the video off command but that have no material effect on the actual operation of the software However we need a third method of dealing with features tha
235. tion of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted AMOS Terminal System User s Guide 15 20 Terminal Control Commands 15 73CENT SIGN CHARACTER TCRT 1 72 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 740NE QUARTER CHARACTER TCRT 1 73 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substi
236. tions channel which can simultaneously and independently transmit and receive data Most modern terminals are full duplex in that data can be transmitted from the keyboard while it is being received by the screen display half duplex Refers to a communications channel which can both transmit and receive but not simultaneously hidden attribute A display enhancement that does not occupy a terminal screen position Hidden attributes are most often associated with character attributes interface board A hardware device that does the actual data transfer from the computer to the terminal AMOS Terminal System User s Guide 2 Glossary interface driver A machine language program that transfers data back and forth between the interface board and the terminal job The structure AMOS uses to allocate time a resources to a user In order to make use of AMOS you must have a job job control block JCB A data structure allocated by AMOS for each job maintaining specific information about that job monochrome terminal A CRT terminal which displays text in a single color only This color can be vary from green to white to amber reverse video A special terminal display attribute that can be used to highlight text on a terminal screen On a monochrome terminal that usually has a black background text displayed in reverse video will be displayed as black text on a light background On a terminal that usually has a l
237. to computer users is probably the RGB or Red Green Blue system Based on various mixtures of these three primary colors it is the system on which color television is based Because most of the technology behind color terminals comes from the color AMOS Terminal System User s Guide Using Color Effectively Page 5 17 television world RGB is the system employed internally in color computer terminals Despite that fact that it attempts to mimic a portion of the human visual system the three color receptor photopigments it is not an intuitive system Given a color described by its RGB components most people would not be able to tell what should be changed to make the color a bit yellower a description that a human can readily understand It is important to note here that no color system can exactly describe all possible colors All color description systems are at best a compromise with some being superior to others Likewise any mathematical color description system can be converted into another via a mathematical transformation This fact is depended on in color television where the picture tube deals with colors in terms of Red Green Blue RGB descriptions but where the color signal is broadcast in terms of chrominance luminance intensity IYQ The electronics in the television receiver simply convert one representation to the other If you have a VCR connected to your television it even deals with colors in a third representation All
238. to take advantage of function keys but also to work on a variety of terminals the AMOS terminal service system has been specially tailored to handle function keys in a terminal independent fashion 9 1 GENERAL CONCEPTS In order to allow programs to make use of function keys a way had to be found to pass unique codes corresponding to the function keys to the applications program On most terminals this unique code consists of a two or three character sequence such as an ASCII escape character followed by another character The problem with using such a method is that the two character sequence is ambiguous it can easily be confused with the same sequence generated by the operator pressing the two keys in sequence The only difference between this and the function key is the timing relationship between characters To require the applications program to monitor this timing relationship is not satisfactory To solve this problem AMOS has been assigned the task of monitoring this timing relationship It in turn translates the two or three character sequence into a truly unique non ambiguous code that is then passed to the applications software This unique code is represented by a character with the high order bit set to one This unique code will correspond to a given function key on a particular terminal s keyboard It is important to note however that the code is unique to that particular type of terminal that is the F1 key on an AM 60 migh
239. trix form on a terminal Screen are not easily recognizable by many people Abbreviations mnemonics and acronyms should not include punctuation e g CPU not C P U Better still avoid the use of such shortcuts and jargon Make sure that the words in displayed messages are short meaningful common and spelled out Also make sure that the words are not ambiguous or confusing Jargon should be avoided whenever possible Make sure that the messages displayed exhibit all the characteristics of good writing Just because it on a computer does not mean that it can be illiterate or even inelegant The sentences should be eBrief simple and clear eComplete eDirectly and immediately usable eAffirmative ein an active voice Nonauthoritarian eNonthreatening eNonpatronizing eNonpunishing eStructured so that the main topic is near the beginning eCautious in the use of humor 4 5HARDWARE CONSIDERATIONS Once a screen has been designed it must be implemented on the terminal hardware to be used with the system Unlike those who deal with the printed word we are somewhat limited in the ways in which we can display information The printed page can display a variety of text styles in different sizes and orientations as well as special characters lines charts photographs and just about anything else you can think of Typically we are limited in display size most often to something approximating 24 lines by 80 columns in choice of characte
240. turn to the normal character set AMOS Terminal System User s Guide Terminal Control Commands Page 15 7 On terminals which do not have an alternate character set mode this call may perform no function as the TCRT call which output the special characters are completely self contained However to maintain compatibility with all terminals you must always issue a TCRT 1 23 before using the special character calls and always terminate such use with a TCRT 1 24 15 25DISABLE ALTERNATE CHARACTER SET TCRT 1 24 This call disables the display of the alternate character set which was enabled by a previous TCRT 1 23 call Any characters displayed after this call will be displayed in the normal character set Like the TCRT 1 23 call this call may perform no function on certain terminals For compatibility however you must use this call after outputting special characters 15 26SET HORIZONTAL POSITION TCRT 1 25 This is an obsolete call no longer supported or used by Alpha Micro provided software It is only present for historical reasons 15 27SET VERTICAL POSITION TCRT 1 26 This is an obsolete call no longer supported or used by Alpha Micro provided software It is only present for historical reasons 15 28SET TERMINAL ATTRIBUTES TCRT 1 27 This call sets the default attributes for the top status line and the main display area of the screen When used it is followed by two argument bytes the first of which sp
241. tuted 15 750NE HALF CHARACTER TCRT 1 74 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted 15 76DEGREE CHARACTER TCRT 1 75 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is not available on a particular terminal either the closest approximation of the character or a space will be displayed In all cases however this call will cause the display of some character occupying exactly one screen position On terminals which do not have this character available a space is normally substituted AMOS Terminal System User s Guide Terminal Control Commands Page 15 21 15 77TRADEMARK CHARACTER TCRT 1 76 This call is only valid when the alternate character set has been enabled via a TCRT 1 23 The results of using this call when the normal character set is enabled are unpredictable If this character is no
242. uent data to the printer port designated in Setup Mode as well as displaying it on the screen While in this mode the terminal also passes any data received from the serial printer port back to the host port The terminal indicates that it is in a print node by displaying PRNT in the upper right corner of the top status line Bidirectional print mode is normally cleared by sending the exit command 71 174 but entering Setup Mode on the terminal will also clear it AMOS Terminal System User s Guide Terminal Control Commands Page 15 47 15 172EXIT BIDIRECTIONAL PRINT MODE TCRT 1 174 This call disables the bidirectional print function which was invoked via the 1 173 call After issuing this call all data will again be displayed only on the screen and not sent out the printer port 15 173SET TERMINAL TIME TCRT 1 175 VERSION 2 00 AND LATER This call sets the AM 65 s internal clock as used by the Toolkit Alarm Clock The Toolkit calendar has a fixed initial month and cannot be set by command 15 174SET TERMINAL DATE TCRT 1 176 VERSION 2 00 AND LATER This call sets the date inside the AM 72 s calendar based on the current system date 15 175SELECT COLOR PALETTE BY HLS VALUE TCRT 1 177 This call selects which of the 64 available colors you wish to select for the 16 color display palette You can change any of the 16 palette indices individually or as part of a group or you can reset the entire palette to its power u
243. ufacturer The terminal driver source code contained on the standard AMOS release stored in account DSKO0 10 2 will also provide examples of how various features are handled AMOS Terminal System User s Guide CHAPTER 2 HOW AMOS INTERFACES TO TERMINALS To connect your software to your terminal AMOS uses several different layers of software and hardware All of these layers together are referred to as the terminal service system While these layers are intended to be transparent to the user and programmer some background on the various pieces and a description of the functions of each can lead to a clearer understanding of how the terminal service System functions This chapter attempts to provide that information 2 1THE HARDWARE INTERFACE The very first thing your terminal connects to is the hardware interface contained within your Alpha Micro computer This serial interface converts the signal voltages from your terminal to data which the computer can more easily understand Several different types of serial interfaces are available for the Alpha Micro computer each having different capabilities although the basic function performed by each is essentially the same In the majority of cases neither the programmer nor the user of the Alpha Micro need be concerned with the particulars of the serial interface in use 2 2INTERFACE DRIVERS Because there are a variety of different serial interfaces which can be used on the Alph
244. uld be used since that command is present in virtually all AMOS Terminal System User s Guide Terminal Control Commands Page 15 33 modern terminals 15 116END UNDERSCORED REVERSE VIDEO TEXT W O A SPACE TCRT 1 115 This call disables the underscore and reverse video text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 This call is similar to the TCRT 1 103 command but does not occupy a screen position This function is available only if the TD UND TD RVA and TD NSP bits are set in the terminal capabilities flags Because this command cannot be supported by many terminals presently installed programs should avoid using this call except where absolutely necessary In situations where the characteristic of not occupying a screen position is not vital the corresponding attribute call which does occupy a space should be used since that command is present in virtually all modern terminals 15 117START UNDERSCORED REVERSE BLINKING TEXT W O A SPACE TCRT 1 116 This call enables the underscore reverse video and blinking text attributes without occupying a screen position As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this comman
245. updated All validation of the size of the box to be drawn is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will have unpredictable results AMOS Terminal System User s Guide Terminal Control Commands Page 15 25 This function is available only if the TD BOX bit is set in the terminal capabilities flags 15 94SCROLL BOX UP ONE LINE TCRT 1 93 This command allows you to scroll a rectangular area of the screen by copying that area up one line This is useful when using a rectangular area of the screen as a window onto text To scroll an area of the screen up one line first position the cursor at the upper left corner of the area to be scrolled Issue a TCRT 1 93 call followed by height and width codes taken from Table B 5 defining the lower right corner of the area to be scrolled The text within the rectangle will now be moved up one line Note that the last line in the rectangle has been duplicated by the copy operation If you wish the last line to be cleared your program must perform that operation itself All validation of the size of the box to be scrolled is left to the application program Using this command with a box specified such that it will extend beyond the visible screen boundaries will have unpredictable results This function is available only if the TD BOX bit is set in the terminal capabilities flags It has no other r
246. ut takes place in the vertical dimension The column insert and delete functions are only available if the TD KID bit is set in the terminal capabilities word 13 7BOX COMMANDS When formatting a screen display for easy readability it is often helpful to use the line drawing characters to help identify groups of similar items on the screen Often boxes are drawn around items to group them and make it easier for the terminal operator to identify like items While this can improve the readablity of the screen repetitive drawing of boxes on the screen can consume much time resulting in the application appearing slow irrespective of the actual speed of the software For this reason some terminals such as the AM 62A support a set of commands which can be used to draw and maniuplate boxes on the screen All validation of the size of the boxes used in these commands is left to the application program Using these commands with a box specified such that it will extend beyond the visible screen boundaries will have unpredictable results These functions are available only if the TD BOX bit is set in the terminal capabilities word 13 7 1Drawing Boxes One command allows you to draw a box on the screen This box encloses a rectangular area of the screen with line drawing graphics characters Note that only the outside lines of the box are drawn on the screen character inside and outside the box are unaffected by this command If you wish to cl
247. utput from terminal printer port commands 15 188SELECT SECONDARY PRINTER PORT TCRT 1 190 When using a workstation as a terminal emulator this call selects the second printer port e g LPT2 as the port to receive all output from terminal printer port commands 15 189SELECT 161 COLUMN DISPLAY MODE TCRT 1 191 This call selects 161 column display mode to determine if this call is available you must first retrieve the terminal features bitmap not TC FLG and test the appropriate bit for the presence of this specific TCRT call RE Please note that some versions of the terminal driver for the AM 75 which supports 161 column gt mode erroneously assigned this function to a different TCRT number This has been corrected in the version supplied with AMOS 2 2 15 190RESERVED FUNCTIONS TCRT 1 192 THROUGH TCRT 1 255 These functions are reserved for future expansion by Alpha Micro If you have a specific need for a new TCRT function you may contact Alpha Micro to reserve a TCRT call number The reservation process avoids problems arising from incompatible extensions to the TCRT functions 15 191SET FOREGROUND COLOR TCRT 2 N This call selects the foreground color to be used for all further text display The call takes an eight bit argument n which specifies the color to be selected The range of values for this argument can be obtained via the TRMCHR monitor call or the TRMCHR XCALL routine from AIphaBASIC It is assumed that for all color
248. very human request should be acknowledged every system reaction clearly described Feedback is the critical ingredient for shaping a person s performance AMOS Terminal System User s Guide 4 2 Principles of Effective Screen Design Self explanatory Steps to complete a process should be obvious and where not supported and clarified by the system itself Reading and digesting long explanations should never be necessary Forgiving system should be tolerant of the human capacity to make errors at least up to the point where the integrity of the task or system are affected The fear of making a mistake and not being able to recover from it is a primary contributor toward human fear of dealing with computers Efficient Eye and hand movements should not be wasted Attention should be directed to relevant controls and displays of information Visual and manual transitions between various System components should proceed easily and freely Flexible People should be able to structure or change a system to meet their particular needs Inexperienced people may wish to confront and use only a small portion of a system s capabilities until they have become more familiar and comfortable with it With experience they may wish to use additional features Available Like any tool the computer must be available if it is to be effective Any system unreliability no matter how good normal system performance will create dissatisfaction in the
249. way from blue causes us to experience the color yellow 5 2 4Colorblindness The term colorblind is often used to describe the color deficiencies affecting some individuals A concern about colorblindness is often used as an objection to the wide use of color since 6 896 of the male population has some kind of color perception difficulty Colorblindness is usually an inheirited defect which affects less than 196 of the female population Not all causes of color deficient vision are known however some are related to the cones and their photopigments A rare form occurs when the blue photopigment is missing The most well known defect however is red green deficiency which occurs when either the red or green photopigment is missing Lack of either photopigment causes the same color discrimination problem however for people lacking red photopigment long wave stimuli appear much darker More common than a missing photopigment is a photopigment where the spectral response curve differs significantly from normal The so called red green color blind man may simply have very low sensitivity to differences in the red green part of the spectrum This will probably be most apparent at low light levels and with values of colors which are in reality only barely discernible as different by the rest of the population In fact there are enough color perception differences among the population in general to explain the common situation of two people differ
250. where the special character is to be displayed 2Enter the Alternate Character Set Mode via the TCRT 1 23 command 3Send the command for the character you wish to display TCRT 1 38 through 1 53 or TCRT 1 64 through 1 78 4Continue sending alternate character commands until you are finished with the line or until you need to reposition the cursor Repositioning the cursor includes carriage return line feed backspace cursor addressing commands and any other command which causes the cursor to move except outputting the special character or course 5Exit the Alternate Character Set Mode via the TCRT 1 24 command Repeat this sequence steps 1 through 5 until you are finished AMOS Terminal System User s Guide 11 2 Using the Alternate Character Set 11 2THE LINE DRAWING CHARACTERS The line drawing characters are used for drawing boxes rules and lines The character assignments are as follows Command Code Symbol Displayed 1 38 Top left corner 1 39 Top right corner 1 40 Bottom left corner 1 41 Bottom right corner 1 42 Top intersection 1 43 Right intersection 1 44 Left intersection 1 45 Bottom intersection 1 46 Horizontal line 1 47 Vertical line 1 48 Center intersection 1 52 Double horizontal line 1 53 Double vertical line 11 3THE BLOCK GRAPHICS CHARACTERS The block graphics characters are typically used for filling in areas of the screen for bar ch
251. wn it is important that any program which manipulates the color settings first save the original color settings and restore them upon exit The current color settings can be determined by using the TRMCHR call 10 4USING AM 70 COMPATIBLE COLOR SELECTION The AM 70 color alphanumeric terminal uses a different method for selecting colors than the one described above Based on an older technology the AM 70 implements colors as field attributes This means that changing colors occupies a screen position reducing the amount of text that can be placed on the screen In addition since the colors are actually implemented in hardware as attributes you lose the ability to use other terminal attributes such as blinking or underlining Because there is a limited number of attributes available the color selection is also limited you can select eight different colors of text on a black background or black text on a background of eight different colors While quite limited in its ability to display colors flexibly the advantages of having any color at all can outweigh the rather severe limitations in the color selection For those applications which can benefit from color 16 TCRT calls have been defined through which you can select color on an AM 70 terminal The TCRT calls 1 132 through 1 139 are used to select different colors of text on a black background The calls are assigned as follows 1 133 select white text on black background 1 1
252. xistent feature 16 2 1Substituting One Feature for Another Particularly in the area of terminal attributes it may be possible to substitute an existing terminal feature for one that is missing For example if a specific terminal does not support the underscore attribute it may be desirable to replace it with a different but appropriate attribute which the terminal does have Care must be taken in this area however as the visual results with an arbritrary applications program are impossible to predict and may be neither visually pleasing or appropriate For this reason this type of substitution is not recommended except is special circumstances where the application software to be used is known in advance Specifically since applications software may rely on the use of an attribute for a specific visual effect attributes should not be substituted or changed if they are all present 16 2 2Emulation by Combining Features In some circumstances it may be possible to combine two or more features a terminal does have to emulate one feature it does not have For example a mode terminal which does not require a screen position to select an attribute can emulate the attribute TCRT calls which do occupy a screen position by simply outputting a space along with the attribute selection Remember that the correct order for this emulation is to output the space and then the attribute start command and the attribute end command and then the spac
253. y one screen position This is done to assure text will properly line up irrespective of the terminal attribute style This function is available only if the TDSUND and TD BLN bits are set in the terminal capabilities flags Because this attribute is present on the vast majority of modern terminals many programs simply assume that it is present and do not bother to check for the terminal capabilities flag which says whether it is truly present or not For this reason all terminal drivers will support this call at least to the extent of outputting a space to ensure that text is properly aligned even if the attribute is not present in any form AMOS Terminal System User s Guide 15 28 Terminal Control Commands 15 103START UNDERSCORED AND REVERSE VIDEO TEXT TCRT 1 102 This call enables both the underscore and the reverse video text attributes As with all attribute commands there are certain differences between field and mode oriented terminals which affect the use of this command For further information on the differences which you must allow for see Chapter 3 Regardless of whether a terminal is field or mode oriented this call will always occupy one screen position This is done to assure text will properly line up irrespective of the terminal attribute style On color terminals the reverse video attribute reverses the foreground and background colors For example if the currently selected colors are a white foregroun

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