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HiSoft C - sinclair

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1. Port I O int imp port_number int out data port_number System Interface void_exit n Some Functions for 32 bit number arithmetic void long multiply c a b void long_add t c a b void long init a nl n0 void long _ set a n d void long copy c a Pseudo Random Number Generator int rand void srand n Spectrum Graphics and Sound Functions Chapter 5 void plot on x y void line on dx dy int ink colour int paper colour void cls void beep duration pitch Errors Introduction The List of Error Messages ERROR 0 missing x ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR ERROR 16 sI RESTRICTION floats not implemented bad character constant not a preprocessor command LIMIT macro buffer full can only define identifiers as macros RESTRICTION macros may not have parameters cannot open file RESTRICTION cannot nest includes missing while not in loop or switch not in loop not In switch LIMIT too many case statements multiple default statements goto needs a label multiple use of identifier direct execution not possible when translating 18 LIMIT name table full 19 20 21 222 23 24 25 26 O72 28 29 30 Ae 239 335
2. 34 35 LIMIT too many types duplicate declaration type mismatch duplicate declaration storage class mismatch LIMIT global symbol table full LIMIT too much global data duplicate declaration LIMIT local symbol table full the variable was not in parameter list undefined variable s bad function return type no arrays of functions LIMIT expression too complicated LIMIT expression too complicated bad type combination bad operand type need an ivalue not a defined member of a structure ERROR 36 expecting a primary here ERROR 37 undefined variable ERROR 38 need a type name ERROR 39 need a constant expression ERROR 40 can only call functions ERROR 41 does not follow a properly ERROR 42 Destination of an assignment must be an ivalue ERROR 43 need a to follow a check bracketing ERROR 44 need a pointer ERROR 45 Illegal parameter type 62 ERROR 46 RESTRICTION Floating Point not implemented 62 ERROR 47 cannot use this operator with float 62 ERROR 48 bad declaration 62 ERROR 49 storage class not valid in this context 62 ERROR 50 62 ERROR 51 duplicate declaration of structure tag 62 ERROR 52 use a predeclared structure for parameters 62 ERROR 53 structure cannot contain itself 63 ERROR 54 bad declarator 63 ERROR 55 missing in function declaration 63 ERROR 56 bad formal parameter list 63 ERROR 57 type should be function 63 ERROR 58 63
3. 40 As explained above the Spectrum memory may well be in a strange state after a translated C program has run Any BASIC program that was there is likely to have been destroyed That is why the C program resets the machine If you know of a safe place to go when the C program finishes then just put an inline jump at the end of your program For instance inline OxC3 25200 will start the C program again 12 8 Error Message Sacrifice The compiler produces explanatory error messages when it detects an error in the program These messages are held in memory Larger programs can be compiled if this memory is released to the compiler and there is a compiler control line to do error After this errors will produce only the error number until the compiler is reloaded Page 32 HiSoft ZX C User Manual 13 Implicit declarations 14 Types revisited 14 1 Structures end unions 14 2 Functions 14 3 Arrays pointers and subscripting 14 4 Explicit pointer conversion Pointers are 16 bit Z80 memory addresses and can be converted to integers which are also 16 bit There are no alignment restrictions since the Z80 Is a true byte addressed machine Pointers are stored in the normal Z80 way with the least significant byte at the lower address 15 Constant expressions The HiSoft C compiler evaluates expressions at compile time rather than at run time when it recognizes them to be constant It recognizes individual constant operands and it rec
4. Use E30 ENTER to edit line 30 and then press x as before to enter the insert sub mode at the end of the line Now press DELETE CAPS SHIFT and 0 to delete the semicolon and press ENTER to leave the insert sub mode and press ENTER once more to leave the edit mode if we look at the line we set that it no longer has the offending semi colon so we can attempt compilation yet again It works Or at least it seems to Don t execute the program yet but press SYMBOL shift to indicate end of source file to the compiler Up springs another error message error 27 undefined variable s The offending identifier is print on Line 470 It should of course be printf Edit the line using E 470 ENTER and insert the requisite f in the proper place using the techniques already discussed The final compilation now produces an error free program at least as far as the compiler is concerned and it can be run by pressing SYMBOL SHIFT followed by Y k counts the words in a given file The other features of the editor are all in their turn useful and it is a good idea to experiment with it as much as possible As the editor is such a powerful program building tool it is vital that you can use it with familiarity and ease Page 22 HiSoft ZX C User Manual Chapter 3 HiSoft C Language Reference Differences from Kernighan amp Ritchie Note the following overriding restriction not otherwise mentioned Floating point is not implement
5. These commands nest so that as long as an included file has an equal number of list and list lines it will not affect the listing of a program that includes it 12 6 Direct Execution There is an additional Feature in HiSoft C that permits the direct execution of statements compiled by the compiler This is sometimes called immediate execution and is similar to typing a command in BASIC without a line number A preprocessor control line is used to enable this feature direct and to disable it direct When in direct mode a sequence of statements is complied instead of the normal sequence of external definitions Note that after a statement has been executed the result will not be apparent unless it is printed So printf x 190 42 would be a useful statement to execute However any changes to global variables will remain so it might be sensible to execute count 10 before some other statement Note also that global variables will not be initialized to zero Page 30 HiSoft ZX C User Manual 12 7 Object Code Translation The compiler normally compiles a program and expects it to be executed with the compiler still resident in memory Often this will be contrary to requirements as the program may be too large to co reside or more usually it may be intended as a standalone program which would normally be loaded and run by itself without the necessity of the compiler having been loaded first Use of the preprocessor comman
6. ERROR 59 63 ERROR 60 LIMIT no more memory 63 ERROR 61 RESTRICTION assignment or move to init automatics 64 ERROR 62 Cannot initialize this disallowed storage class 64 ERROR 63 Cannot initialize this disallowed typo 64 ERROR 64 too much initialization data 64 ERROR 65 bad initializer need a 1 64 Common Mistakes In C Programs 64 Appendix A The Plus 3 67 Technical Details or the Files Stored 67 New Library Routines 67 Graphics Library 67 ROM Floating Point Routines 68 The Reverse Polish Calculator 70 Converting Cassette HiSoft C Programs To 3 Disks 70 Appendix B Breaking Into Running Programs 71 BASIC Listing of BREAK Program 72 Welcome Congratulations on buying the HiSoft C compiler We hope that you will find a product that meets your needs and that you are pleased to have bought We arc proud to have made another popular language available to many new friends We have tried to make this product useful reliable and easy to use and with your help we will constantly improve it in the future Your comments will play a very important part in deciding what direction to follow in its development We welcome any feedback whether it is praise or criticism We need to know which features you like which you don t and what new ones you d like to see This C compiler is a substantial and complex program and whilst we hope that it is perfect we recognize that in practice there may be some teething troubles We
7. You will probably now want to try a longer program perhaps out of Kernighan and Ritchie and to do that we suggest that you turn to the next chapter on using the editor rather than typing straight to the compiler By now we hope that you have seen that the compiler is sitting just behind your keyboard and everything you type is sent straight to it One thing that you will often want to type to the compiler is include to make it compile a program that you have created using the editor or if you have put the program onto a tape as a file called fred then just type include fred When calm prevails again please read the chapters on the language and on the library or at least skim through them so that you have a general idea what is there You can read the chapter on errors when the need arises of course you may never need it The Spectrum Keyboard The keyboard is used in lower case mode all the time Pressing one of the keys delivers the ASCII code of the corresponding lower case letter or the digit The space key is unaltered However pressing the Enter key delivers a value of 10 corresponding to NEWLINE or LINE FEED rather than a value of 13 corresponding to CARRIAGE RETURN This is because C uses the NEWLINE character in as a line terminator rather than the CARRIAGE RETURN r Symbol shift is altered slightly pressing SYMBOL SHIFT together with another key always delivers the ASCII code of the red symbol engraved on or
8. k3 k1 k2 etc is a list or constant expressions which will be put into the output code An expression which has a value in the range 0 to 255 inclusive will cause a single byte in be generated and any other number will cause two bytes to be generated Any constant expression may be used see section 15 For example to jump to location 0 inline OxC3 0 0 1 CxC3 is the Z80 JP instruction or to call location 1601 hex with 3 m the A register open stream 3 on a Spectrum define CHAN OPENOx160 define Id a with Ox3E define callOxCD inline Id_a_with 3 call CHAN_OPEN and to Store an input character in a global variable c define Id_mem_from_hl 0x22 inline call getchar Id_mem_from_hl amp c Page 28 HiSoft ZX C User Manual Be careful when using this facility Consult the low level section in this manual to find out which registers need saving etc 10 External definitions 10 1 External function definitions There is an addition to the syntax of function definitions which provides a way of defining functions which take a variable number of actual arguments these are calledvariadic functions The reserved word auto can follow the function declarator before the function body i e between the f and the int arg The effect is to cause the compiler to place the number of bytes or actual arguments as an additional argument after the rest The function can access this argument and use it to work out how
9. restrictions are given in the Language Reference chapter of this manual A fifth kind of error is a compiler error We hope that these will be rare but include advice here in case you find one It may be indicated by an error message starting with the word COMPILER or with a number not in the list below No details of these messages are given since they may vary from time to time They result from internal checks in the compiler Of course a compiler error may not be to well behaved as toproduce an error message but may cause the compiler to crash or loop etc if you think that this has happened first try again after reloading the compiler from tape incase it has been corrupted if the problem persists then please contact HiSoft we will be pleased to help you it will be easier to help you if you have clear details The List of Error Messages ERROR 0 missing x This is a slightly special message because the x character can vary The message says that the compiler believes that a particular character should come nest in the program and it doesn t Examples are missing at the end of a statement or a missing in a function call Some care is needed to understand the message properly The compiler is reading the program from the beginning and cannot see the rest of the program beyond the place that it has reached so it has to decide what error message to produce on the basis of what it has seen so far This limitation together with our desire
10. the program i e if there is a forward reference to it So it is possible to have a library file of functions and automatically include only those that are needed by a particular program Note that if some functions In a library say f call other functions in the library say g then f should be before g Otherwise it will be necessary to search the library again For an example of this kind of library look at the standard function library delivered with the compiler Another variation without a filename is used to compile source that has beenprepared with the editor and is now in its memory text buffer include includes can only be nested once because of limited file buffer space So from direct entry level it is possible to lnclude a program which in turn uses Include for aheader file or for functions but these files may not use Include Note that because there is only one cassette recorder it is not possible to have one file on tape include another file on tape 12 3 Conditional compilation Conditional compilation control lines are not implemented The library search facility provides a way to achieve conditional compilation 12 4 Line control line control lines are not implemented 12 5 Listing Control There is an additional facility in HiSoft C to control the production of a listing by thecompiler The compiler will normally produce A listing but list will turn it off To turn It back on use list
11. 3 8 Prices Royalties Publishing and Copying 8 Example Programs 9 The Sieve of Eratosthenes 9 Numeric Conversion 10 RS 232 system 10 Bibliography 13 Chapter 2 The Editor 15 Introduction to the Editor 15 Cassette and Microdrive Commands 19 An Example Session using the Editor 20 Chapter 3 HiSoft C Language Reference 23 Differences from Kernighan amp Ritchie 23 1 Introduction 23 2 Lexical Conventions 23 3 Syntax notation 24 4 What s in a name 24 5 Objects and ivalues 24 6 Conversions 24 7 Expressions 25 8 Declarations 26 9 Statements 28 10 External definitions 29 11 Scope rules 29 12 Compiler control lines 29 13 Implicit declarations 33 14 Types revisited 33 15 Constant expressions 33 16 Portability considerations 33 17 Anachronisms 33 The Compiler Preprocessor 33 define lt Identifier gt lt macro gt 34 error 34 list 34 direct 34 include 36 include filename 36 translate filename 36 Other Preprocessor Commands 36 Explanatory Notes 36 Type Checking 36 Low Level Interface 36 Chapter 4 HiSoft C Standard Function Library 39 Arithmetic functions 39 int max n auto 39 int min n auto 40 int abs n 40 int sign n 40 An Illustration of How to Grub Around In a Store 40 char peek address 40 void poke address value 40 Format conversion routine 40 int atoi s 40 Sorting function a Shell sort 41 void qsort list num_items size cmp_func 41 String Handling Functions 41 char
12. N2 being specified The editor remembers the previous numbers and strings that you entered and uses these former values where applicable If you do not specify a particular argument within the command line The values of N1 and N2 are initially set to 10 and the strings are initially empty If you enter an illegal command line such as F 1 100 hello then the line will be ignored and the message Pardon displayed you should then retype the line correctly e g F1 100 hello This error message will also be displayed if the length of S2 exceeds 20 if the length of S1 is greater than 20 then any excess characters are ignored Commands may be entered in upper or lower case The various commands available within the editor are described below note that wherever an argument is enclosed by the symbols lt gt then that argument must be present for the command to proceed Text may be inserted into the text file either by typing a line number a space and then the required text or by use of the command Note that if you type a line number followed by ENTER i e without any text then that line will be deleted from the text if it exists Text is typed in lines and each line can have up to eighty characters in it If you get to the end of a screen line then the screen will be scrolled up and you may continue typing on the next screen line The DELETE CAPS shift 0 key can be used to delete the character just to the left of the cursor an
13. Note that the Z80 Instruction in r c is used so that the full 16 bit port address can be used Int out data port_number Sends the bottom 8 bits of data to the I O port specified by the 16 bit port number Note that the instruction out c ris used so that the full 16 bit port address can be used System Interface void_exit n This function immediately exits from the program and returns to the system The argument is printed as the corresponding BASIC report e g exit 0 is OK and exit 4 is Out of memory Some Functions for 32 bit number arithmetic These functions are not intended to provide full facilities for long arithmetic but are here because they are needed by the random number generator They can provide a base if 32 bit numbers are needed The numbers are represented by an array of fourcharacters or a pointer to such an array The least significant eight bits are held in array 0 and so on to the most significant eight bits in array 3 The numbers are unsigned this only affects the multiplication routine void long_multlply c a b char a b c Multiply two 32 bit numbers c as b void long_add c a b char a b c Add two 32 bit numbers c a b Page 52 HiSoft ZX C User Manual void long_init a n1 n0 char a unsigned n1 nO Initialize a 32 bit number n1 provides the most significant 16 bits and nO provides the least significant 16 bits So for example after long_init 0x1234 0x56
14. Page 60 HiSoft ZX C User Manual int n char s 20 scanf d 19s amp ni s This will read an integer into n amp n points to n and a string which must not belonger than the array s into s The two fields must be separated by a comma and maybe some white space Note the use of the maximum width 19 to protect against an overlong input string Note that there was no ampersand amp preceding s in the scanf call as b is already a pointer to the array Notes on the use Of SCANF scanf uses getchar to read characters and this is important to remember getchar is a buffered function which doesn t pass across any input until the enter My is pressed The enter key is always passed across after the rest of the line as a C NEWLINE character n So the scanf control string should almost always start with a space character to match the NEWLINE character left behind at the end of the previous line of input Don t put the space character at the end of the control string because then scanf will carry on scanning until it finds something that isn t white space before you haveprompted for the next input EOF handling is badly behaved the safe thing to do is to call getchat after scanf In order to see if you have reached end of file if not you can use ungetc to put backthe character you read There is no u conversion for scanf d is used for both cases Using a u by mistake can produce obscure sympto
15. a predefined type or a type def name as argument it will not accept an anonymous type name such as int To move an exiting C program to this compiler give the type a name in a typedef declaration and add the word cast before the parentheses to compile a program using this syntax with another compiler define the word cast to mean nothing thus define cast The sizeof operator has a similar syntax and only accepts a predefined type or a type def name It will not accept an anonymous type or an expression So the syntax is unary expression cast type specifier expression sizeof type specifier These differences do not restrict the programs that can be written but simply require them to be written in a particular style 7 3 Multiplicative operators This compiler is like those described in the reference manual in that the remainder of a division operation has the same sign as the quotient Thus truncation is towards zero 7 4 Additive operators 7 5 Shift operators An arithmetic shift is performed when an int is right shifted so that the result has the same sign as the original A logical zero fill shift is performed when an unsigned is right shifted HiSoft ZX C User Manual Page 25 7 6 Relational operators 7 7 Equality operators Just like most other compilers the nil pointer or null pointer is actually 0 zero as well as conceptually so and in consequence pointers which may point at location zero in memory
16. array or structure by copying the contents of a static array Note that a static variable is preferable to an automatic one unless the function is recursive or space allocation dictates an automatic A structure initializer is a series of constants which generate bytes like inline see 9 14 They are not aligned on field boundaries Initialization is performed each time the complete program is run It is not performed in direct mode 8 7 Type names The only type names permitted are those of the predefined types and those declared In a typedef declaration Abstract declarators are not allowed They can be replaced by a typedef declaration where they occur in existing programs with a resulting increase in clarity and type security 8 6 Typedef HiSoft ZX C User Manual Page 27 9 Statements 9 1 Expression statement 9 2 Compound statement Declarations are only permitted at the head of a function body and are not allowed inother compound statements 9 3 Conditional statement 9 4 While statement 9 5 Do statement 9 6 For Statement 9 7 Switch statement There can be no declarations at the head of the enclosed statement 9 8 Break statement 9 9 Continue statement 9 10 Return statement 9 11 Goto statement 9 12 Labeled statement 9 13 Null statement 9 14 Inline Statement HiSoft C provides the ability to incorporate machine code into C programs A new type of statement which looks like a function call is used inline k1 k2
17. attempt to compile it We won t explain the program in too much detail here as it is not appropriate Load the C system and enter the editor by pressing edit followed by ENTER You will be presented with a gt prompt and a flashing L cursor Type i10 10 ENTER to start inserting text at line 10 with a line increment of 10 The line number is displayed on the screen along with a space and the cursor Type in the lines below exactly as you see them pressing the enter key at the end of each line Blank lines are entered into the text file by simply typing ENTER with no text 10 An example editor session 30 define EOF 1l 50 i 80 int c i count inword 100 char s 20 120 static int fp 140 do 150 i 160 printf Filename 189 i GF 190 while c getchar n 210 s i c 220 if i 19 break 230 250 s ij 0 270 fp fopen s r 280 if fp 0 290 i printf nFile not found n 310 while fp 0 330 count inword 0 Page 20 HiSoft ZX C User Manual 359g while c getc fpji i E Ff 350 370 if i isspace c 380 inword GO 390 else if inword 0 400 410 inword 1 420 ecount 430 440 450 fclose fp 460 470 print nWords d n count z 4BO Now this program contains four errors three of which could be described as syntax errors See if you can spot them before going any further Once the program is entered leave INS
18. beginning of the line ENTER end the edit of this line keeping all the changes made Q QUIT the edit of this line ignoring all the changes made and leaving the line as it was before the edit R RESTORE the Line as it was originally forgetting all changes made on this line L LIST the rest of the line being edited You remain in the Edit mode with the cursor re positioned at the start of the Line K KILL delete the character at the current cursor position Z delete all the characters from and including the current cursor position to the end of the line INSERT characters at the current cursor position You will remain in this sub mode until you press ENTER this will return you to the main Edit mode with the cursor positioned after the last character that you inserted Using delete within this sub mode will cause the character to the left of the cursor to be deleted In this mode the cursor changes to a X this advances the cursor to the end of the line and automatically enters the Insert sub mode described above Page 14 HiSoft ZX C User Manual C CHANGE the character at the current cursor position and then step along to the next character The next character that you type will overwrite those already in the line until you press enter whence you are taken back to the Edit mode with the cursor positioned after the last character you changed The DELETE key just moves the cursor back one character in this mode Whilst
19. by the key rather than the BASIC keyword This Includes the lt lt gt and gt symbols on the Q M and E keys which have been assigned values of 29 31 and 30 respectively They can be used in your programs instead of the two character combinations lt and gt Symbol SHIFT pressed with the key returns the end of file value EOF 1 and is echoed as Chr 137 on the display This is used to terminate files typed in from the keyboard particularly source which is input to the compiler On output to the display the value of 255 is made to produce a CHR 137 symbol rather than the COPY keyword This is so that if a program tries to output the C EOF value an obvious pattern results C end of file or EOF has the value 1 and an attempt to output this causes it first to be truncated to 255 CAPS SHIFT is also altered slightly Pressing CAPS SHIFT together with 6 normally delivers a value of 10 but this value is now delivered by the ENTER key CAPS SHIFT and 6 now produces 16 The values delivered by pressing CAPS SHIFT together with 0 or 5 are reversed so that CAPS SHIFT 0 DELETE delivers 8 whilst CAPS SHIFT 5 cursor left delivers 12 HiSoft ZX C User Manual Page 5 Files on the Spectrum This section discusses the way in which HiSoft C has been fitted to the Spectrum and focuses on the input output system which is the main part of the tailoring we start out with a basic knowledge of the Spectrum and of the
20. cannot be easily tested against NIL 7 8 Bitwise AND operator 7 9 Bitwise exclusive OR operator 7 10 Bitwise Inclusive OR operator 7 11 Logical AND operator 7 12 Logical OR operator 7 13 Conditional operator 7 14 Assignment operators The compiler does not allow the assignment or pointers to Integers or vice versa except for the assignment of 0 zero to pointers as NIL This restriction is designed to make it less likely that the wrong value will be assigned to a pointer e g missing or amp operator and thus less likely that the store is overwritten in consequence An explicit type conversion can be used to make pointers point at particular areas of memory typedef integer location location ptr ptr cast location Oxbc00 7 15 Comma operator The comma operator is not implemented 8 Declarations In accordance with normal C programming style any storage class specifier in a declaration must come before any type specifier s So the syntax for a deci specifier is deci specifiers sc specifier opt decl specifiers type specifier Page 26 HiSoft ZX C User Manual 8 1 Storage class specifiers The extern specifier has a restricted use since there are no separate files It is used in the special case of library functions of non int type These functions have not been defined when they are used in a program because they will be defined when the library file is searched at the end of the program see section 1
21. character indicates the interpretation of the input field and the corresponding argument must be a pointer to satisfy the call by value rules of C The following are the legal conversion characters d A decimal integer is expected the corresponding argument should be an Integer pointer o An octal integer with or without the leading zero is expected the Corresponding argument should be an integer pointer x A hexadecimal integer with or without the leading Ox is expected the corresponding argument should be an integer pointer h A short integer is expected in this implementation the corresponding argument should be an Integer pointer c A single character is expected this reads the next input character regardless of whether it is white space or notand assigns it to the char variable pointed to by the corresponding argument S A character string is expected the corresponding argument should be a pointer to a character array large enough to hold the string and the terminating 0 which will be added The conversion characters a o and x may be preceded by 1 which in compilers supporting long integers would mean that the argument points to a long integer rather than a normal integer Here it is ignored The function returns when the control string is exhausted or when some input does not match the control specification It returns as its value the number of successfully assigned input items A short example of scanf is shown here
22. count 0 for j 0 j lt SIZE j flag j TRUE for j 0 j lt SIZE j if flag j TRUE prime j 4 3 for k j prime k lt SIZE k prime flag k FALSE discard multiples COunt printf td primes n count HiSoft ZX C User Manual Page 9 Numeric Conversion This program is not particularly elegant but allows the user to enter a decimal number of up to five digits which will subsequently be printed out in both hexadecimal base 16 and binary base 2 The readn function which reads the decimal number in is very unsophisticated and surprisingly easy to crash If more than five digits are entered or if one or more of the characters read in are not digits then the results are quite unpredictable Herein lies one of the golden rules of C you can do literally anything but any bugs are entirely your problem A program to convert a decimal number to hexadecimal and binary main int n char b 1i7 printf nGive me a number J n readn binary n b printf nThis is tx in hex and s in binary n n BP int readn reads in a decimal number of up to 5 characters i char s 5 int i c total i 0 while cegetchar n s ie c total 0 for c O0 c lt i c total total 10 s c 0 return total binary num digits converts a number to a binary string int num char digits or char digits int i c
23. default is right justify 0 a leading zero on following field use 0 instead of space for padding 999 a digit string minimum field width 999 the precision max number of characters from a string L long data has no effect Note that a character is printed by putting in the control string This function is built in void fprintf fp control arg1 arg2 FILE fp char control Behaves like printf except that output is performed using the file pointer fp instead of stdout This function is built in void sprintf s control arg1 arg2 char s char _ control Behaves like printf except that output is placed In the string s Instead of being sent to stdout The character array pointed to by s must be large enough to receive the output or store will be overwritten This function is built in int scanf control arg1 arg2 char control ALL OTHER args MUST BE POINTERS HiSoft ZX C User Manual Page 49 This Function is the input analogue of printf providing many of the same conversion facilities in the opposite direction It reads characters from the standard input Interprets them according to the format specified in control and stores the results in the remaining arguments which must all be pointers The control string usually contains conversion specifications which are used to direct interpretation of input sequences It may contain Blanks white space which are matched by any amount of
24. definition of the language It is also a good tutorial introduction to C in the second capacity it is very useful to any user of C and in the first capacity it is absolutely essential This manual is written on the understanding that you have a copy of the book Full details of the book are given in the Bibliography C Itself is a general purpose programming language that places the emphasis on concise programs and flexible expressions The user is provided with little protection it is possible to write elegant powerful programs but it is also possible to write amazingly obscure bugs this is what makes it so powerful The HiSoft implementation of C is a compiler designed with small home computers very much in mind It creates a useful tool on a system that has only RAM and a cassette tape available Other extras are also supported The key to providing a useful tool is the same as with other HiSoft language products The compiler is based entirely in RAM Together with an editor the source text which is being developed and the resulting machine code There is no intermediate pass through assembly language or linkers such as is normally found in C compilation systems This means that program development can be very rapid indeed The implementation is designed to be as close to the definition given in the C Reference Manual as possible The C Reference Manual is Appendix A of the Kernighan amp Ritchie book mentioned above There is a chapter
25. directly by the ROM but we have added some functions and these are available directly with the C names in the second column above For example strconvert 4 2 strconvert 3 4 calculate print Is the equivalent to print 4 2 3 4 in BASIC Internally the Spectrum uses 5 byte strings to store numbers and we have provided the following to access these directly push c pushes a 5 byte value on the stack pop c l l pops the top value on the stack into a 5 byte string HiSoft ZX C User Manual Page 69 int foconvert a Converts the top value on the stack to ASCII in the string a without a null terminator and returns the length as the result calc n Performs the Spectrum ROM operation n The Reverse Polish Calculator To compile the Reverse Polish calculator compile RPNTEST C The main body of thesource code is in RPN C This also uses the input function from input a Input a m reads in a buffered string into a of maximum m You can easily modify this to suit youron taste as far as cursors etc are concerned The calculator lets you use all the features of the calculate function from the keyboard For a full list of these see the RPN C file For example 12 34 45 ENTER 2070 34 6T int ENTER 34 Converting Cassette HiSoft C Programs to 3 Disc We have provided a utility to convert cassette HiSoft C source files to disk This is runusing from 3 BASIC The program loads the next c
26. for i 15 i gt 1 4 cmnum 6 1 lt lt i progressively divide by 2 digits i 7 2 0 digits 16 0 RS 232 system This program must be used as follows Before loading the C compiler set the baud rate of the RS 232 using FORMAT baudrate from Basic and then open channel 4 to the serial line as follows OPEN 4 b Page 10 HiSoft ZX C User Manual Now load the compiler and enter or Load this program Once it has been compiled files may be sent and received along the RS 232 line as required This program is ideal if you create your source files on another machine such as a QL or BBC Micro and have no other way of sending the text to the Spectrum Remember that if you ever leave the compiler and return to BASIC then you can return to the compiler without losing any text in memory by typing RANDOMIZE USR 25200 and pressing ENTER Send and receive files to and from the RS 232 line The serial channel must be set up to 4 first define FILE int Manifest constants for program define EOF 1 define UNIXEOF 4 tdefine CPMEOF 26 main execution starts here int c i sw ueof char s 20 FILE fp do printf Filename i Q while c getchar n read in filename until ENTER pressed s it c if i 19 no more than 19 characters break b s i 0 end of string marker printf nPress n0 for read nl for write n pr
27. line See RPNTEST C for an example Graphics Library The graphics library has the following functions flash 1 bright 1 inverse 1 Change the screen attributes printed as in BASIC at x y positions the cursor to column x line y Tab y moves to column y on the current line perm temp copies the temporary attributes to the permanent attributes and vice versa If you do not understand what this means don t call these routines cline 1 clears the bottom 1 lines of the screen cscroll 1 Scrolls the bottom l 1 lines of the screen by one line 1 must be at least 2 HiSoft ZX C User Manual Page 67 circle on x y r draws a circle centre x y radius r and in either the current ink or paper depending on the value of on If on is TRUE i e non zero then the ink colours are used and if on is FALSE i e zero then the paper colours are used This works in an analogous way to the plot and line commands in the standard library draw on x y d draws an arc from the current pixel position to a point x pixels across and y pixels upthrough an angle of d radions on specifies the colour as usual intpoint x y returns a value in dictating whether the pixel x y is set to the current ink nonzero or paper colour 0 int attr x y returns a value indicating the attributes at the given character Attribute value is papertink 8 bright 64 flash 128 intscreen x y returns the character code corresponding to the ch
28. particular This function is built in void move dest source length char dest source unsigned length This function moves the contents of the area of the store starting at source into the area starling at dest It moves length bytes The copy is done to the non destructive direction if the areas of store overlap i e starting at the low end if dest is below source and the high end if dest is above source This operation is similar to strcpy but it always copies the given number of bytes including any zero bytes it finds This function is also faster because it is built in Input Output Functions These functions implement UNIX type file input output They are all similar to those described in Kernighan amp Ritchie and consequently that is a good place to find more details There are three main groups of functions the character level functions the complex level functions and the raw level functions The character level functions are those most used In C programs they provide buffered input and output of single characters The complex level functions use the character level functions to provide more facilities ranging from output of a string puts to flexible formatted printing printf The raw level functions provide the interface to the facilities available in the computer and are used by the character level functions Page 46 HiSoft ZX C User Manual Input output in C is done via files which is a fairly general concept F
29. strcat base add 41 int stremp s t char strcpy dest source unsigned strlen s char strncat base add number int strncmp s t n char strpbrk s1 s2 int strspn s1 s2 int strespn s1 s2 Character Test and Manipulate Functions int isalnum c int isalpha c int isascii c int iscntrl c int isdigit c int islower c int isprint c int ispunct c int isspace c int isupper c char tolower c char toupper c int isgraphic c int isxdigit c char toascii c char strncpy dest source number char strchr string ch char strrchr string ch Storage Allocation and and Freeing Heap Management char calloc n size char malloc n void free block char sbrk n Miscellaneous Functions void swap p q length void move dest source length Input Output Functions Character level Input Output Functions FILE fopen name mode int fclose fp int getc fp int ungetc c fp int pute c fp int getchar int putchar c Complex level I O Functions void exit n char fgets s n fp void fputs s fp char gets s void puts s void printf control argl arg2 void fprint fp control argl arg2 void sprintf s control argl arg2 int scanf control argl arg2 int fscanf fp controlargl arg2 int sscanf s control argl arg2 Raw Level I O Functions int rawin int keyhit
30. structure again to supply the actual arguments to the function In any case Page 62 HiSoft ZX C User Manual ERROR 53 structure cannot contain itself You can include one kind of structure directly inside another but to build a list using structures use pointers to structures such as struct list int value struct list nest ERROR 54 bad declarator Check the syntax of a declarator in the C Reference Manual ERROR 55 missing in function declaration A function declaration as opposed to a function definition must have a after the name and may not have a parameter list A function declaration just says that a particular identifier is of type function returning something whilst a definition contains identifiers of type function returning something whilst a definition contains the body of the function as well Functions can only be defined at the outermost level of a program whereas a function declaration can occur as a member of a structure or a parameter etc ERROR 56 bad format parameter list The format parameter list of a function is just a list of identifiers Additional type information is given in a separate declaration afterwards just before the body of the function ERROR 57 type should be function The compiler believes that this is a function definition and has discovered that the function name is not of function returning something type Check what is allowed in the C Reference Manua
31. temporarily halted The system may also be used as a quick method of entering the compiler from BASIC CAPS SHIFT SPACE is quicker than typing RAND USR 25200 the program may be deactivated by a call or RAND USR to address 65306 The program works by switching the Spectrum into interrupt mode 2 This means that there is no extra code in any programs produced and so the keyboard checks are not saved with any compiled programs It is suggested that you make two copies of the loader one with and one without the code for keyboard checking Should you want to use keyboard scans with your compiled program the scanning program may be loaded and activated exactly as above HiSoft ZX C User Manual Page 71 BASIC Listing of BREAK Program 5 CLEAR 65020 10 DEF FN a a CODE a 48 7 aS gt 9 20 DEF FN b a 16 FN a a 1 FN a a 2 30 POKE 65021 FN b C3 POKE 65022 FN b 21 POKE 65023 FN b FF 35 LET tor 40 FOR n 65281 TO 65359 50 READ a 60 LET awFN b a 710 LET tot totta 80 POKE n a 90 next n 100 IF tot lt gt 11691 THEN PRINT CHECKSUM ERROR 1000 DATA ES C5 F5 21 noon FE 06 00 3E FD 77 1010 DATA 23 10 FC 77 36 FE ED 47 ED SE F1 1020 DATA C1 E1 c9 ED 56 3E 36 ED 47 C9 FS 1030 DATA 3E FE DB g9 npn 3g WOT ap WTF DB FE 1040 DATA 1F 30 03 F1 FE C9 AF DB FE F6 EO 1050 D
32. the features of the language and of course includes many functions which take advantage of the ZX Spectrum s graphics and sound capabilities The descriptions of related functions are grouped together and there is also an index of all functions The library comes in three parts the built ins the header and the library proper The built ins are functions which are in the run time package for efficiency and aretherefore always contained in your program and can simply be called The most important built in is printf for formatted output The header is a C source file called stdio h provided on the compiler tape It contains constant and type definitions for the library and also contains the min and max functions It should be included include stdio h at the start of all programs which use the library The library proper is also supplied as C source in the file stdio lib on the compiler tape It contains the source of most of the library functions This file should be selectively included at the end of each program which uses the library by means of alibrary search control line include stdio lib The function library for the HiSoft C compiler will continue to grow and become more powerful with time One of the best ways for the library to grow is by new functions created by the people who use the compiler If you write functions that youthink will be useful to other people then send them to us We will collect these functions and dist
33. the maximum of the sizes of all the members of the union All members will be aligned at the lowest address i e any spare space for a particular member will be at the high end of the union Memory Layout The compiler and stand alone programs translated using the compiler all load at25200 and are entered there also This address leaves space below the compiler for two Microdrive channels or one Microdrive channel and a cassette pseudo channel There is also room for a very small BASIC program The compiler will use store up to RAM TOP and it moves RAM TOP down beneath itselffor protection This means that it is necessary to CLEAR to a larger value if you want touse the Spectrum for BASIC again after leaving the compiler Translated programs use the memory between 25200 and the RAM TOP value which was set before using the compiler to translate the program However these programs do not move RAM TOP themselves Page 38 HiSoft ZX C User Manual Chapter 4 The HiSoft C Standard Function Library This chapter of the HiSoft C Reference Manual describes the functions that are provided with the compiler The function library provided with a C compiler is very important since it adds to the power of the Language This library like those or most other compilers is patterned after that of the Unix C compiler Many of the functions are also described in Kernighan amp Ritchie some In great detail The library also serves to illustrate some of
34. where it shouldn t be A can appear after a label name or after a case expression or it can appear in an expression as part of the e1 e2 e3 conditional expression This one seems to be part of an expression but doesn t match a Check the precedence of the expression if you think it does match a The simplest way is to put extra parentheses in to make sure Remember that conditional expressions group right to left if they are nested ERROR 42 Destination of an assignment must be an ivalue A special case error message to let you know as soon as possible that the left hand side of this assignment expression is not an ivalue The rules about what an ivalue is are given in the C Reference Manual but roughly speaking an ivalue is a memory address which can be stored into Remember in particular that an array name and a function name are not lvalues ERROR 43 needa to follow a check bracketing The compiler expected to find a colon as part of an e1 e2 e3 conditional statement and it hasn t done so Remember in particular that e2 cannot be an assignment expression unless it is bracketed and that conditional expressions group right to left if they are nested HiSoft ZX C User Manual Page 61 ERROR 44 needa pointer In order to use indirection on an expression it must be a pointer to something The indirection may be an explicit operator but it could also be implicit In a gt operator or an array element reference e1
35. 2 2 However their type must be declared before they are used otherwise they will be implicitly declared as function returning int So an extern declaration must be made at the start of the program This declaration is made in the library header file for the standard library functions This declaration does not cause the function to be loaded from the library only actual use of the function does that The register specifier is accepted but ignored since the compiler has no registers available for variables 8 2 Type specifiers The specifiers long and short are accepted but ignored A long Int and a short int are thesame as an int i e 16 bits 8 3 Declarators 8 4 Meaning of declarators 8 5 Structure and union declarations Fields often called bitfields are not implemented It is necessary to use bitwise operators and shifts to access particular bits in a byte The names of structure tags and members share the same name space as ordinary variables so a structure cannot have the same name as an integer for example 8 6 Initialization Initializers are provided for static and external variables but not for automatic variables The initialization of automatic scalar variables should just be replaced by anassignment statement The initialization of automatic aggregates i e stack based local arrays and structures is not permitted in C but HiSoft C provides move in the function library and this can be used to initialize a local
36. 78 a has the value 0x12345678 void long_set a n d char a unsigned n d Initialize a 32 bit number n provides 16 bits to initialize and d tells where to place them in the number For example after long_set a 0x1234 1 a has the value 0x00123400 and lonq_set a 0x5678 3 gives a the value 0x78000000 void long_copy c a char a c Copy one 32 bit value to another place Equivalent to c a Pseudo Random Number Generator This generator is adapted from Learning to Program in C by Thomas Plum It generates 16 bit numbers with a period of 2432 So it generates a sequence ofnumbers which repeats itself after every 2 32 calls Note that the same numbers will occur again and again in the sequence No guarantees are given about the distribution of the random numbers so don t be disappointed Int rand Returns a 16 bit pseudo random number void srand n Seeds the generator Used at the start of a program to begin at a different place inthe sequence each time This makes the programs behavior change in differentruns if the same seed n is used then the sequence will be exactly the same as the previous time this can be useful in some statistics programs Spectrum Graphics and Sound Functions These functions are not part of the standard C Library but have been provided to allowthe user to take full advantage of the machine possibly for games writing void plot on x y int on xX y HiSoft ZX C User Manual P
37. ATA 30m 20 Tin WIE BF DB FE iF 30 WEE WIE 1060 DATA TF DB FE jpn 38 F2 Fl CD AF 0D 63 1070 DATA 70 62 Page 72 HiSoft ZX C User Manual
38. C input output functions The functions provided in the standard library are modeled after those provided on Unix systems Input and output in C is done serially via files These files cover not only what is normally thought of as files on tape disc etc but also input from the keyboard and output to the display Input and output on the Spectrum is organized in a similar way via streams The notable exception on the Spectrum is cassette tape which has no stream However the HiSoft C compiler provides access to the cassette in the same way as access to other devices This goes some way towards making input and output appear to be device independent as far as the C programmer is concerned There are three standard files in a C program These arc the standard input stdin the standard output stdout and the standard error output stderr These are assigned to the keyboard stream the upper display screen and the upper display screen again respectively Some translations are done on the characters Input and output to other devices is done to files using file pointers The file pointers used for input and output in C are used to represent stream numbers on the Spectrum They have type pointer to file so that they are compatible with file pointers on other systems but actually their value as a bit pattern is just the Spectrum stream number Characters are input from the keyboard using the standard function getchar and output to the display using
39. ERT mode by pressing EDIT and then return to the compiler by typing c and pressing ENTER Now compile the program by typing include and pressing ENTER The first thing we see is that the compilation stops at the line containing the call to fopen with error 32 bad type combination Seasoned C programmers will immediately notice that the declaration of fp in line 120 is wrong it should be a pointer so we have to put an asterisk immediately in front of fp To do this re enter the editor by hitting ENTER and entering the editor in the usual way Now edit line 120 by typing E120 ENTER The line appears on the screen along with its line number and below this is the line number again followed by a flashing cursor We want to step along the line and insert a before p so repeatedly press CAPS SHIFT B or a E until the cursor is directly below the f of fp Now press i and watch the cursor change to a flashing to indicate INSERT sub mode Now type the asterisk and press ENTER The cursor stays where it is but changes back to a flashing L again Press ENTER again and the altered line is entered as it is displayed on the screen The cursor returns to the main editor and the machine awaits another command Go back to the compiler C and ENTER and try compiling the program again It progresses quite smoothly but suddenly stops with error 0 missing right after displaying count It does this because the while immediately above th
40. INTEGRATED COMPILER EDITOR Suitable for all ZX Spectrums including 48K 128K and Plus 3 models HiSoft High Quality Software HiSoft C Fast Interactive Compiler for the Sinclair ZX Spectrum System Requirements Any ZX Spectrum Computer including the Spectrum 3 Copyright HiSoft 1984 1990 Printing History lst Edition November 1984 Reprinted frequently 2nd Edition February 1988 Reprinted July 1990 Set using an Apple Macintosh with Microsoft Word amp Aldus PageMaker All Rights Reserved Worldwide No part of this publication may be reproduced or Transmitted in any form or by any means including photocopying and recording without the written permission of the copyright holder Such written permission must also be obtained before any part of this nature publication is stored in a retrieval system of any It is an infringement of the copyright pertaining to HiSoft C and its associated documentation to copy by any means whatsoever any part of HiSoft C for any reason other than for the purposes of making a security back up copy of the object code as detailed within this manual Table of Contents Welcome 1 Plus 3 Version 1 Chapter 1 Introduction 3 Getting Started Read this First 3 Cassette Version 3 Disk Version 4 Loading and Running the Compiler on the Plus 3 4 General 4 The Spectrum Keyboard 5 Files on the Spectrum 6 Screen Colours 7 Making a Backup 7 Making a Backup on the Plus
41. Spectrum screen printf nFile received n the end b These examples are small pieces of C programming designed to impart the flavour of the language Once you have studied them and know how they work the whole world is open to you Remember that there is just about nothing that you can t do in C Page 12 HiSoft ZX C User Manual Bibliography The C Programming Language Brian Kernighan amp Dennis Ritchie Prentice Hall 1978 ISBN 0 13 110163 3 Contains the essential C Reference Manual and is a useful tutorial text Learning to Program In C Thomas Plum Prentice Hall 1983 ISBN 0 13 527847 3 A good tutorial book which starts from first principles The Complete Spectrum ROM Disassembly lan Logan amp Frank O Hara Melborne House 1983 ISBN 0 86161 1160 Indispensable if you want to call the Spectrum ROM routines Master Your ZX Microdrive Andrew Pennell Sunshine Books 1983 ISBN 0 946408 19 X A useful equivalent to Logan amp O Hara for the Interface 1 ROM C ata Glance Adam Denning Chapman amp Hall ISBN 1 85058 035 9 An excellent beginner s tutorial book at a reasonable price 8 95 HiSoft ZX C User Manual Page 13 Page 14 HiSoft ZX C User Manual Chapter 2 The Editor Introduction to the Editor The editor supplied with HiSoft C is a simple line based editor designed to be easy to use and to give the ability to edit programs quickly and efficiently The editor allows you to work on a progra
42. a do or a while or a for This continue isn t inside one ERROR 12 not In switch case and default introduce the action for particular values in a switch statement They can t be used outside a switch HiSoft ZX C User Manual Page 57 ERROR 13 LIMIT too many case statements There is a limit of 50 case statements active at once A case is active from when it occurs until the end of the switch enclosing it Several switch statements in succession provide a way round this limit e g ERROR 14 multiple default statements Each switch statement can only have one default statement inside it ERROR 15 goto needs a label Every goto statement must have a corresponding labeled statement somewhere in the same function body ERROR 16 multiple use of Identifier An identifier that is used to label a statement or as the label in a goto statement cannot be used as a variable name either global or local to the same function as the label as well The converse is also true ERROR 17 direct execution not possible when translating When you are translating a program for stand alone execution it is not possible to use direct ERROR 18 LIMIT name table full The compiler has a table which holds the name of every active variable macro and label in the program This table is now full Global variables and macros i e define names take space from their declaration to the end of the program but local names only take space whilst t
43. a function which will compare two items in the list For example the standard function strcmp can be used if the items are strings The function should take two pointer arguments so a call looks like cmp_func x y and the function should return an integer 1 if x lt y 0 if x y 1 if x gt y A common structure for the list is a two dimensional array num_items long and size bytes wide char list num_items size The function is described in detail in Kernighan amp Ritchie String Handling Functions Remember that strings in C are arrays of characters which end at the first zero byte The array may well have more physical store after the end char strcat base add Char base add Inserts a copy of the string add at the end of string base This is a physical copying and it is your responsibility to make sure that there are enough bytes at the end of base to take the copy of add otherwise whatever is next will be overwritten The function returns a pointer to the start of the base string as its result Int strcmp s t char s t Compares two strings byte for byte and returns 0 if the two are identical it returns a value gt 0 if s gt t and a value lt 0 if s lt t A string is greater if the first character that differs is later in ASCII code sequence char strcpy dest source char dest source Makes a physical copy of the source string in the dest string HiSoft ZX C User Manual Pa
44. able subject when writing programs In this chapter of the manual we discuss errors in general then provide a detailed list of the error messages that can be produced by the compiler and what they mean Finally we discuss same common errors in C programs and their consequences Introduction When you ask the compiler to compile your program it will scan through your program recognizing the various constructs that you have used and generating appropriate code for them Whilst doing this it may find an error in your program If the compiler does find an error it will display an error message like this ERROR nn error message text There are three parts to the error message First the word ERROR just lets you know that this is an error message Secondly the error number nn tells what the compilerthinks is wrong and let s you find more information about the error in the nextsection of this manual Thirdly is the error message text which is a brief indication of the cause of the error In many cases it will be all that you need to work out what is wrong and how to correct it After displaying the error message the compiler will wait for you to press any key and will then return to its sign on message unless you choose to do an automatic edit of the line see the Editor chapter The error message texts take up a significant portion of the computer memory approx 2 kilobytes and there is a facility to reclaim this The control line error w
45. age 53 This function sets the pixel at screen location x y to either the current ink colouror the current paper colour depending on the value of on which is TRUE i e nonzero for ink colour and FALSE i e zero for paper colour Void line on dx dy int on dx dy Draws a line from the current plot position is a point dx pixels to the right or left if dx is negative and dy pixels up or down if dy is negative The current plot positionis the pixel where the last plot or line function stopped The on parameter behaves as it does with the plot function Int Ink colour int colour Changes the current ink colour using the Spectrum colour codes black 0 blue 1 white 7 No action is taken for an invalid colour code The new colour is returned as the value of the function or else ERROR 1 is returned if the colour code was invalid The function only changes the temporary attributes Int paper colour int colour Changes the current paper colour in the same way as ink works void cls This function clears the upper screen of the Spectrum Void beep duration pitch int duration pitch Makes sounds using the loudspeaker in the Spectrum The duration is given in tenths of a second whilst the pitch is given in Hz Hertz so that concert A 440Hz is 440 For example A pitch of 0 causes a period of silence a rest Page 54 HiSoft ZX C User Manual Chapter 5 Errors Errors are an important and all but inevit
46. aracter at the character square x y ROM Floating Point Routines The MATHS lib library contains some routines to call the Spectrum ROM floating point code These routines have the advantage that there is still a reasonable amount of RAM left for your programs This would not be the case if we built the floating point into the compiler We have also provided an example of their use in RPN C See below for details strconvert a pushes the value of the ASCII string a onto the calculator stack For example strconvert 4 2 will push 4 2 onto the stack print 0 pops a value off the stack and displays it in ASCII calculate op takes a character parameter and performs an operation normally on the top two elements of the stack Possible values of op are Page 68 HiSoft ZX C User Manual add subtract multiply divide pop and print the last value like print x to the power y S sin C cos T tan s arc sin arc cos arc tan In e exp integer part like INT in BASIC square root Sign like SGN in BASIC abs modulus duplicate top of stack exchange top two values delete top value display top of stack leaving on the stack U ACT Lt E TMANVOXQA09QA7FT7T7 FO gt I FI log log ten x 10 x crt cube root sqd x squared x toz y the root of x reciprocal 1 x pi pi hsn sin h hcs cos h htn tanh has arc sin h hac arc cos h hst arc tan h Most of the above are supported
47. ask you in particular to take the trouble to write to or phone us with a clear description of any problems as soon as you can so that we can find and fix as many as possible before the next version We will be offering our normal upgrade service as we produce new versions In the meantime we wish you all the best and hope that you find as much pleasure and new knowledge in using the compiler as we have found in developing it Plus 3 Version The Plus 3 version of HiSoft C is supplied on disk For details on the additions and changes relevant to the Plus 3 please see Appendix A HiSoft ZX C User Manual Page 1 Page 2 HiSoft ZX C User Manual Chapter 1 Introduction This manual describes an implementation of the programming language C on the Sinclair ZX Spectrum 48K 128K and Plus 3 models The manual is divided into a number of chapters which each discuss one major aspect of the compiler This first chapter provides a general introduction Following that is a chapter on the editor and how to create programs The third chapter is a detailed description of the C dialect accepted by the HiSoft C compiler in the fourth is a description of the extensive range of functions supplied with the compiler in the standard library Finally there is a chapter devoted to errors the messages they produce and how to find them The C Programming language is the title of a book by Brian Kernighan and Dennis Ritchie which currently provides the only real
48. assette file from the tape and attemptsto use the same name for the disk file If the file name is not a valid 3DOS filename then the file is saved as TEMP c Page 70 HiSoft ZX C User Manual Appendix B Breaking into Running Programs Here is a program designed to run with the compiler which will give the user the ability to halt and break into a running C program or a compilation listing The program is provided as a short BASIC program To use it simply type in the listing as shown and save it Now RUN the program if the words CHECKSUM ERROR appear then a mistake has been made in typing the DATA statements When the programs successfully RUN type in the line SAVE INTS_C CODE 65021 340 for tape or SAVE M 1 INTS_C CODE 65021 340 for Microdrive Having created the code file you should now alter The BASIC loader called cc At the start of the loader line 1 for tape and line 3 for Microdrive the following statements should be inserted CLEAR 65020 LOAD INTS_C CODE RANDOMIZE USR 65281 for tape or CLEAR 65020 LOAD M n INTS_C CODE RANDOMIZE USR 65281 for Microdrive When the program has been activated by a call to address 65821 pressing CAPS SHIFT and SPACE together will halt any program Then pressing ENTER will resume execution or pressing SPACE will cold start the compiler exactly as though the user had executes a RAND USR 25200 from BASIC Thus both compilation listings and running programs may be
49. bles linkage and arguments from the stack The result of the function is returned in HL and also In BC There is a variation on this mechanism which is used for variadic functions i e those that take a variable number of arguments In this case after pushing all the arguments on the stack the caller pushes the total number of bytes of arguments Including two bytes for the total itself This total appears as the last argument to the called function The called function can use the total to access its other argument and must use it to discard the arguments from the stack before returning Register Usage Neither the compiler nor the compiled code use the alternate register set the IY register or the or R registers These registers are used by the Spectrum I O system and in particular the IY register must always point at ERR_NR The compiler and the compiled code run with interrupts enabled The stack pointer SP is used normally and stack discipline should be observed The IX register is used as a frame pointer as described above The HL register is used to return the value of expressions and particularly function results The BC DE A and F registers are used as general working registers Data Storage There are three kinds of data storage constant static and automatic Storage for constants is allocated inline with the generated code this includes numbers characters and strings HiSoft ZX C User Manual Page 37 Static
50. char toascii c char c Forces the character into the range 0x00 to 0x7F by AND ing it with Ox7F char strncpy dest source number char dest source int number Copies exactly number characters into dest If source contains less than number characters then it is copied in its entirety to the beginning of dest and the remaining characters are filled with nulls 0x00 if source contains number or more characters then the first number are copied to dest and dest is not null terminated i e It s not really a string any more just a character array char strchr string ch char string ch Returns a pointer is the first occurrence of the ch in the string or NULL 0x0C if thecharacter does not occur You can get a pointer to the end of a String by looking forthe NULL character pointer_to_end strchr string 0 You can use this function in any situations where you would use the SET type in Pascal For Instance to loop while hexadecimal digits are input we might write C while strchr 1234567890abcdefABCDEF character getchar do_something_with_character Pascal while input4in O 9 a f A F do begin DoSomethingWithCharacters get Input end Page 44 HiSoft ZX C User Manual Of course C provides a much neater way of solving this particular problem while isxdigit character getchar do_something_with_character char strrchi stringf ch char stri
51. command above Note that the line range and the two strings may have been set up previously by any other command so that it may only be necessary to type F ENTER Cassette and Microdrive Commands These commands use the same simple scheme as the compiler to distinguish between cassette files and Microdrive files If you want to use a Microdrive file called say FRED which is on Microdrive 2 then put the drive number and a colon before the filename when giving commands thus 2 FRED PUT TEXT TO CASSETTE OR MICRODRIVE Command P m n s Text in the line range m to n is put onto cassette or Microdrive using the filename specified by the string s Remember that these arguments may have been set by a previous command The line numbers are not put into the file Before entering this command make sure that your tape recorder is switched on and in RECORD mode GET TEXT FROM CASSETTE OR MICRODRIVE Command G s The cassette or Microdrive is searched for a file with a filename of s when found it is loaded at the end at the current text Line numbers are attached to the lines of the file as they are read in The line numbers go up in steps of 10 They start at 10 If there is no existing text and otherwise the text from tape is put at the end of the already resident text HiSoft ZX C User Manual Page 19 An Example Session using the Editor As a simple example of using the editor provided with the C compiler we ll write a short program and
52. d translate Object_file_name allows for this instructing the compiler to save the program and all the required runtime routines to cassette or MICRODRIVE under the named file This control line must appear at the Start of the program See the section on preprocessor commands for more details Example Stand Alone Program For this example it is assumed that you know how to use the editor and the compiler do not try this example until you have tried those in Chapter 1 and Chapter 2 Supposing you had a Hello World program that looks something like this 10 main 20 30 printf Hello World 40 and have saved it as the file hello c either to cassette or Microdrive using the editor s p command pl 9999 hello c or pl 9999 2 hello c Provided that you know how to compile and run a program with the compiler present a stand alone version can he produced using Microdrive 2 in this example by adding an extra line HiSoft C Compiler 1 3 Copyright c 1984 6 HiSoft translate 2 hello code include 2 hello c main printf Hello world SYMBOL SHIFT 1 When you press SYMBOL SHIFT I the compiler saves the stand alone program to a file on Microdrive 2 called hello code It doesn t matter whether you save to a Microdrive or cassette nor does it matter what the name of the output file is Be careful though any file with the same name as the code file to be produced will be overwritten The process of saving t
53. d can be pressed repeatedly to delete more characters but not beyond the beginning of the text line The text is kept in memory and it is possible to fill up the memory When this happens the compiler will produce a normal error message ERROR 60 LIMIT no more memory To save memory you can put some of the text to cassette or Microdrive or you can use the compilers error feature to sacrifice the error messages and then re enter the editor Once some text has been created there will inevitably be a need to edit some lines Various commands are provided to enable lines to be amended deleted moved and renumbered Most commands are executed immediately but the EDIT E command selects a particular line for further special editing commands INSERT TEXT Command I m n The editor will display line numbers and you can type in text The line numbers start with m and go up in steps of n You enter the required text alter the displayed linenumber using the various control codes if desired and terminating the text line with ENTER When you have typed as many lines as you want press EDIT Caps shift 1 and if you enter a line with a line number that already exists in the text then the existing line will be deleted and replaced with the new line after you have pressed ENTER Ifthe automatic incrementing of the line number produces a line number greater than 32767 then the insert mode will exit automatically Page 16 HiSoft ZX C User Man
54. e master disc away somewhere safe YOU ARE ONLY ENTITLED TO MAKE ONE WORKING COPY Prices Royalties Publishing and copying We are often asked by people whether they would have to pay royalties if they were to sell programs compiled by our compilers The answer is a resounding No After all that s what the compiler is for We are very happy for people to sell compiled programs and we wish you every success We want to help you in every way we can and are very happy to talk to you about products that you are writing We may offer to publish the program for you if we feel that it fits in with our range land is of a high enough quality Or we may be able to suggest another publisher Any compiled programs will include our runtime routines and we do require you to acknowledge our copyright of these on any programs that you publish We d also be very grateful if you mentioned that the program was written using our products Page 8 HiSoft ZX C User Manual What we don t like is theft We sell our products at prices that are very low compared with similar products on other machines The only way that we can do this and continue to produce more products in the future is by selling in volume So please don t make copies for other people The ugliest form of this is copying for money piracy We will do everything we can to stop this and would appreciate being told of any pirate copies that you act Finally would like to apologize to the vast ho
55. e2 Note that the HiSoft C compiler does not permit an integer before a gt as discussed in section 14 1 of the C Reference Manual if you want to access a structure at an absolute store address use a cast to write the expression typedef char char_ptr cast char_ptr Ox005c gt fcb_filename 0 a The idea is to help prevent mistakes which can corrupt memory and to make it easier to transfer programs from one type of machine to another ERROR 45 illegal parameter type There are certain types which cannot be used as parameters to functions These types are structures unions and other functions You can pass a pointer to any of these types ERROR 46 RESTRICTION Floating Point not implemented Sorry ERROR 47 cannot use this operator with float arguments This message will not occur as long as the previous one does ERROR 48 bad declaration Check what is allowed in a declaration ERROR 49 storage class not valid in this context in particular there are no register or automatic globals ERROR 50 There is no error 50 ERROR 51 duplicate declaration of structure tag The same identifier has been used twice as a structure tag ERROR 52 use a predeclared structure for parameters Instead of declaring the contents of a structure in the parameter list declare the structure first and give ita name either a tag or by using typedef Then use the name to declare the parameters You will need the
56. eader block getc and putc can then be used to read or write characters and finally fclose tidies up and writes the last block of an output file The memory for a block buffer is also arranged by fopen and fclose Page 6 HiSoft ZX C User Manual When the system is about to write to cassette it changes the border colour to red for about five seconds before doing so The cassette should be started in RECORD when this happens On input a red border is displayed for about a second to indicate that the cassette should be started in PLAY When the program has read a block the cassette should be stopped so that the program can process the contents of the block and then restarted when it requests the next block The compiler is capable of compiling source from a block even if the cassette is left running Screen Colours The HiSoft C compiler uses the Spectrum temporary colour attributes to control the ink and paper colours on screen These colours are set up from the permanent colour attributes when the compiler displays its sign on message If you want to use a differently coloured screen i e not black ink on white paper then simply set up the colours that you want with INK and PAPER commands before loading the C compiler or use the editor B command to get back to BASIC The INK and PAPER commands should not be embedded in a PRINT command Making a Backup Your cassette is supplied with a lifetime guarantee so if you have any problems loading
57. ed which means that use of types float and double will cause the error restriction floats not implemented to be produced and compilation will terminate 1 Introduction HiSoft C is designed to be very close to the language described in the book The C Programming Language by Kernighan and Ritchie That book is the reference work on C and we recommend that all users of HiSoft C should have a copy of it Because it is recommended that all users of HiSoft C should have a copy of it Because it is close to that definition of C HiSoft C is also close to other dialects of C that exist which are also based on it Other possible reference works are listed in the Bibliography In Chapter 1 Most parts of the Kernighan and Ritchie book apply directly to HiSoft C and we do not repeat the full description here This chapter describes the differences between HiSoft C and the language described in the C Reference Manual which is Appendix A of Kernighan and Ritchie That Appendix is a concise definition at the language and this chapter is a concise definition of the differences More explanation of some aspects is given elsewhere in the manual This chapter is given section numbers in just the same way as the C Reference Manual so that the comments here apply to the corresponding section in that book Where the section heading is given with no comments HiSoft C is just as described in the book We start now with the comments on section 1 HiSoft C is implement
58. ed on the Sinclair ZX Spectrum computer and the Amstrad Z80 computers and CP M machines which use the Z80 microprocessor 2 Lexical Conventions 2 1 Comments 2 2 Identifiers Names External identifiers are used only for forward declaration of the type of a function in HiSoft C otherwise identifiers are just as described 2 3 Keywords No differences Note that keywords must be lower case HiSoft ZX C User Manual Page 23 2 4 Constants 2 4 1 Integer constants No differences but note that long is the same as int see 2 6 2 4 2 Explicit long constants As for 2 4 1 2 4 3 Character constants 2 4 4 Floating constants 2 5 Strings 2 6 Hardware characteristics Z80 ASCII char 8 bits 1 byte int 16 2 bytes short 16 2 bytes long 16 2 bytes tool double range Note that short long int are all the same 3 Syntax notation 4 What s in a name There are two differences in the storage classes The first is that register variables are always treated just like automatic variables because there are not enough registers available to allocate any to variables The keyword register is accepted but ignored so there is actually no difference in the language which the HiSoft compiler accepts The second difference is that all local variables must be declared at the head of a function body and may not be declared at the head of nested compound statements This is not a serious restriction in practice and can be defended on the grounds o
59. ent by element or by the built in library function move In particular the test a b where a and b are arrays such tests whether they have the same base address riot the same contents The test a next is almost certainly an error Remember that local variables and arguments of functions are allocated on the stack and are thrown away as soon as the function finishes executing All arguments to functions are passed by value An explicit pointer must be used to pass a variable parameter Check the number and types of arguments supplied to functions as no checking is performed Check that pointers are supplied where required so that the argument can be changed by the function An amp operator may be required Even if a function has no arguments it must have after its name to call it This will normally be caught as a type error but the statement func_with_no_args just causes the address of the function to be evaluated and thrown away To call the function it is necessary to write func_with_no_args Remember that function return types may be changed automatically by the rules of C In particular int maybe truncated to char Remember that the end of file value EOF is 1 and cannot be tested against a char variable int must be used for the result of getchar getc etc HiSoft ZX C User Manual Page 65 Check whether i or i is appropriate In particular note that a normal loop of N times goes from 0 to n 1 and is
60. equired e g that the members have the same offset in the structures have not been met ERROR 22 LIMIT global symbol table full The compiler has a table which holds details of each global variable in the program The only way to save space in this table is to reduce the number of global variables ERROR 23 LIMIT too much global data There is not enough space in memory or everything that has to fit and more space is needed for global variables Reducing the size of the global variables or the size of the generated code by not compiling as much or the size of the in memory source program by include will all help to give more room In addition using the error control line to sacrifice error messages will give more room ERROR 24 duplicate declaration This name has been declared twice in this function as a local variable or a parameter Choose another name for one of the variables ERROR 25 LIMIT local symbol table full The compiler has a table which holds details of each local variable and label in a function This table is full Space can be saved by reducing the number of local variables in the function which caused the problem perhaps by splitting the function into parts which use fewer variables or by using fewer goto labels none by rewriting using loops and conditionals ERROR 26 this variable was not in parameter list Only those variables which were in the parameter list between the of a function defini
61. es not match any of the case expressions then the statement is just bypassed There is no semicolon between a control statement while if for and the statement that it controls Otherwise the empty statement is controlled It is normally wrong for a define line to finish with a semicolon All arguments to scanf must be pointers That is they must be the address of the variable where the result is to stored Page 66 HiSoft ZX C User Manual Appendix A The Plus 3 This Appendix details any additional information that is needed for use on a Spectrum Plus 3 Technical Details of the Files Stored Files are stored as header less ASCII and terminated by CTRL z 26 decimal which is used for detecting EOF This form is used for ease of transfer with word processors and CP M The editor will normally terminate lines with a single LF 10 decimal character however the compiler will ignore CR s so it does not matter if your files contain these characters The files produced by translate are standard 3DOS code files and may be loaded directly from BASIC After producing or running a translated program you will normally be returned to BASIC with an OK prompt New Library Routines We have supplied some extra library routines that are Spectrum specific These arecontained in graphs lib and maths lib Both these libraries should be compiled using the include facility and should normally be placed just before the include stdio lib
62. expansion is not available error This command effects a once only removal of compiler error messages releasing thespace taken up by these messages to the compiler This would normally only be used if a program were particularly larger Subsequent error detection will result in only the error number being reported rather than the full text list This command is followed by either a or a sign and switches the compiler listing on or off as appropriate These commands may of course be nested so that the common practice of having a list at the start of a header or library file and a list atthe end of it has the desired effect direct This command is also followed by a mandatory or symbol and is used to turn direct execution mode on or off The direct execution mode is almost certainly unique to the HiSoft C compiler and allows programs and functions to be tested as they are written Once a direct command has been issued functions can be invoked variables can be assigned to loops can be run and any other statement can be executed By typing a function name followed by any parameters and a semi colon the function will be executed Normally this will only be useful when the function prints its result direct printf Yu in hex is n 3000 3000 direct will print out the decimal and hex equivalents of 3000 onto the screen direct is used to leave direct execution mode Page 34 HiSoft ZX C User Manual Remember tha
63. ey are declared This notion is also employed when operators such as Indirection and amp address are applied So for example if Int polar 2 typedef complex 2 complex Z int ptr_Cartesian 2 then polar r and ptr_Cartesian are all of equivalent types This is different tosome other languages where they need to have the same named type to be equivalent or to be declared at the same place Structural type equivalence is more flexible but can lead to obscure bugs if misused and it is generally good practice to give a name tocomplicated types by using typedef Low Level Interface This section gives some details of the code produced by the compiler with particularreference to the store layout and use of the machine It is intended to help you interface other programs to C programs and in particular to help you make use of the in line statement Source Format C source is basically just a string of ASCII characters divided into lines by NEWLINE characters 10 often known as LINE FEED There are no CARRIAGE RETURN characters 13 although these will be accepted in a source file by the compiler so other editors and even other computers can be used as tools with which to produce HiSoft C programs Page 36 HiSoft ZX C User Manual File Format Files are provided at the character level i e fopen getc putc fclose On cassette files are stored as a sequence of data blocks which follows a header block The header b
64. f ease of understanding of programs but it also helps keep the compiler small All the fundamental types are provided but as noted above short is the same as int as is long 5 Objects and lvalues 6 Conversions 6 1 Character and integers Sign extension is not performed when converting characters to integers so characters appear as integers in the range 0 255 6 2 Float and double Floating point numbers are not yet available so this section has no relevance Page 24 HiSoft ZX C User Manual 6 3 Floating and integral 6 4 Pointers and integers 6 5 Unsigned 6 6 Arithmetic conversions 7 Expressions The compiler generally computes expressions from the inside out and from left to right but as stated in the reference manual this should not be relied upon as it may change between releases of the compiler Integer overflows are ignored as are attempts to divide by zero Floating point error handling when implemented will depend on that provided by the machine 7 1 Primary expressions Function arguments are evaluated in left to right order and are pushed on the stack as they are evaluated As the reference manual says this order should not be relied upon See the notes for section 7 7 2 Unary operators The syntax of the type conversion operator is different to that described In the reference manual in order to simplify the compiler and make the programs more readable The operator has a name CAST and must be given
65. ge 41 unsigned strlen s char s Returns the length of a string That is the number of characters before the terminating zero char strncat base add number char base add int number Behaves like strcat except that it copies at most number characters The resulting string is null terminated int strncmp S t n char s t int n Behaves like strcmp except that it checks at most the first n characters of the strings It stops earlier if the strings are shorter char strpbrk sl s2 char s1 s2 Returns a pointer to the first occurrence in string sl of any character from s2 or NULL If no character from s2 exist in sl For example strpbrk the quick brown fox jumps over the lazy dog wolf r Will return a pointer to the place marked with int strspn s1 s2 char s1 s2 Returns the length of the initial segment of string s1 which consists entirely of characters from string s2 Int strespn s1 s2 char s1 s2 Returns the length of the initial segment or string s1 which consists entirely of characters not from string s2 Character Test and Manipulate Functions Int Isalnum c char c Returns TRUE i e 1 if the character is an alphanumeric i e a letter or a digit and returns FALSE i e 0 if it is not Page 42 HiSoft ZX C User Manual Int Isalpha c char C Returns TRUE if the character is a letter and FALSE if it is not This function is built in Int Isascii c char c Re
66. gh the named library file looking for previously invoked functions When one is found it is compiled into the current program This means that if one were using the standard library to provide certain functions for a program it would not be necessary to separate all the functions used into a separate file and include that as normal However as the compiler only includes those functions which have been invoked but not defined care must be taken to ensure that any library functions which make use of of other library functions are present in the library file before the subsidiary ones In other words if a program uses a function f and this function calls a further function g in which both f andg are inthe library then the definition of f must occur before that of g The standard library supplied with HiSoft C is constructed in this way so no problems should occur in its use translate filename This preprocessor command tells the compiler that the object code it produces by compiling your program is going to be used as stand alone code so it must save the product of the compilation to tape or Microdrive under the filename given This command would normally only be given once a program has been fully tested as there is little point in having a non working stand alone program HiSoft ZX C User Manual Page 35 In normal operation the compiler stays in memory along with the object code which it is producing In most application
67. he object file unavoidable destroys the compiler in memory The best it can do which it does is to immediately run the translated program this immediately and rapidly illustrates the next two problems HiSoft ZX C User Manual Page 31 Firstly you can t see the output It actually takes place and the message is displayed n the screen but it is cleared from the screen almost immediately thereafter Secondly the Spectrum does a full power on reset The reason for this is that after a program has run it isn t likely to have much to return to in the way of a BASIC program It seems cleanest to do a complete reset You can get around this if you know exactly what you are doing as we shall see The translated program performs all the output that you ask for if it is near the end of your program it will be cleared off the screen very quickly The solution is simply to make the program wait for a while after the output has been displayed A few ways of doing this are shown below 5 sit forever in an infinite loop 10 main 20 30 printf Hello World 35 for S 40 5 wait for a not very long while in a timed loop 10 main 20 25 unsigned i 30 printf Hello World 35 for i l i 1 use nested loops for longer times 40 5 wait until the user says he s finished looking 10 main 20 30 printf Hello World 33 printf nPress a key when you have finished 36 rawin
68. heir function is being compiled So reducing the number of global names will save space and so will breaking up large functions into two or more smaller ones which don t have as many variables each ERROR 19 LIMIT too many types The compiler has a table which holds All the types used in the program and this table is now full These are all types e g int ptr and not just named types Reducing the number of types is the only way to save space perhaps by using the typecast operator to break up more complex pointer chains and so on ERROR 20 duplicate declaration type mismatch This usually means that the name has been declared twice Choose another name for one of the variables It may be an intentional double declaration such as using a function before it is defined in which case the type rules have been broken For example a function used before it is defined is implicitly declared to return an Int and the subsequent definition must confirm this Page 58 HiSoft ZX C User Manual ERROR 21 duplicate declaration storage class mismatch This usually just means that the variable name has been declared twice Choose another name for one of the variables Remember that in C a name can be declared twice sometimes e g when a function is used before it is defined or when the same name is used for members of two different structures and in that case the second part of the message is important It means that in this case the conditions r
69. ile pointer fp If the file is being written to thisensures that the last block of data is written If the file is being read there is noaction on the device In both cases the control and buffer storage becomes available to open another file An example of the use of this function fan be found in the editor example session at the end of Chapter 2 This function is built in int getc fp FILE fp The basic character level input function It reads the next character using the file pointer fp It returns EOF 1 if the end of the file has been reached Note that itreturns an integer not a character If the result is assigned to a character variable EOF will never be seen because the top byte is thrown away leaving 255 instead of 1 This function is built in int ungetc c fp Int c FILE fp This function puts the character c back onto the file fp so that it is the next character to be read with getc or getchar There are a couple of points to note about the use of ungetc you can only put one character back at a time on each file and scanf uses ungetc so you cannot use ungetc after scanf without an intervening call to getc This function is built in HiSoft ZX C User Manual Page 47 Int putc c fp intc FILE fp The basic character level output function Sends the character c using the file pointer fp It returns the character as its result also This function is built in Int getchar Get a character from the
70. iles are Just a stream of bytes which can be read one at a time using getc or written one at a time using putc There are three standard files which all C programs have these are the standard input stdin the standard output stdout and the error output stderr stdin isusually the keyboard and the output files are the screen A program can also open other files on cassette Microdrive etc as available All the files can only be accessed one character at a time serial access See the introductory chapter of this manual for details of the I O system Character level Input Output Functions FILE fopen name mode char name mode Opens a file for character level Input output The string name is the name of the file to be opened and the string mode tells whether the file is to be read or written The file will be opened the reading if the string is r and it will be opened for writing if the String is w It is not possible to append to an existing file and if you open an existing Microdrive file for writing it will first be erased Be Careful mode is a string and not a character fopen returns a file pointer for use with the other functions to tell them which file to write to or read from The file pointer will be MIL i e 0 if there is any error An example of the use of this function can be found in the editor example section at the end of Chapter 2 This function is built in Int fclose fp FILE fp Close the file indicated by the f
71. ill cause the compiler to discard the error messages and put the memory to general use so that you can write larger programs After the compiler has done this an errormessage looks like this ERROR nn The only way to get the error messages back is to reload the compiler You can alwayslook up the error numbers in this chapter of course Some error messages result from a mistake in the sequence of characters that youhave typed e g a missing semi colon These are often called syntax errors Another kind of error results from an inappropriate use of the language and these are called semantic errors e g trying to assign a value to an array identifier The compiler makes no distinction between these two kinds of errors A third kind of error message occurs when your program is too large for the compiler to handle These are compiler limits and are identified by the word LIMIT at the start of the error message text They have been chosen so that the great majority of programs will compile without reaching the limit if you do encounter a limit then try to break up the part of the program concerned More detailed suggestions are given for each individual limit HiSoft ZX C User Manual Page 55 A fourth kind of error message occurs if you write a program which includes a legal C construct that is not implemented by this compiler This it called a restriction an dis indicated by the word restriction at the start of the error message text Details of
72. in Change mode the cursor changes toa F FIND the next occurrence of the find string previously defined using the F command below This sub command will automatically end the edit on the current line keeping the changes if it does not find another occurrence of the find string in the current line If an occurrence of the find string is d string in the current line If an occurrence of the find string is detected in a subsequent line within the previously specified line range then the Edit mode will be entered for the line in which the string is found Note that the text cursor is always positioned at the start of the found string S SUBSTITUTE the previously defined substitute string for the find string where the Cursor is and then search for the next occurrence of the find string This together with the F sub command above is used to step through the text file optionally replacing occurrences of the find string with the substitute string FIND STRING Command F m n f s Text in the line range m to n is searched for an occurrence of the string f the find string If such an occurrence is found then the relevant text line is displayed and the Edit mode is entered see above You may then use commands within the Edit mode to search for Subsequent occurrences of the string f within the defined line range or to substitute the string 5 the substitute string for the current occurrence of f and then search for the next occurrence off see the E
73. in this manual HiSoft C Language Reference Manual which describes in detail the differences between this implementation and the definition There is one main omission floating point arithmetic There is an area of difference linkage of modules There are some minor differences for technical reasons And there is a significant extension direct execution Direct execution or statements has been provided in this implementation It takes advantage of the immediate compilation to let the user type in c and execute it Straight away Just like BASIC Getting Started Read this First Cassette Version To start running the HiSoft C compiler load the cassette into your recorder with the label COMPILER facing upwards and type in normal Spectrum fashion HiSoft ZX C User Manual Page 3 LOAD ENTER Press PLAY on the cassette recorder After the compiler has loaded it will ask you Whether you want to make a copy on Microdrive Type r for the moment Disk Version Firstly make a copy of the disk we supplied you with and then put it away in a safe place never use the original disk for programming keep it as a master so that you will always be able to make a new copy if anything goes wrong Now put your copy of HiSoft C in drive A and type load HISOFT C enter Loading and Running the Compiler on the Plus 3 Reset your Spectrum 3 and enter 3 BASIC Then type LOAD DISK and the compiler will be loaded and executed We do no
74. initions from define lines which are currently being expanded This buffer is now full Try to simplify the macro definitions Note that a circular macro definition can cause this error ERROR 5 can only define identifiers as macros Check what is allowed on a define line In Kernighan amp Ritchie ERROR 6 RESTRICTION macros may not have parameters The compiler can only handle macros which don t have parameters i e those which are a straight token replacement Alternatively you may be trying to use bracketed replacement text and have left out the necessary space define FIFTH_ELEMENNT array 4 is not C define SIXTH_ELEMENT array 5 is C the parenthesis is useful sometimes ERROR 7 cannot open file The compiler cannot find an include file ERROR 8 RESTRICTION cannot nest Includes The compiler permits one level of include for the main program and a further level for header files and functions and libraries These files cannot have a further level included in them ERROR 9 missing while At the end of a do statement there must be the word while do statement while expression The compiler is looking for that while and hasn t found it ERROR 10 notin loop or switch A break statement is used to exit from a switch statement or from a loop such as adoora while or a for This break isn t inside one ERROR 11 notin loop A continue statement is used to go back to the top of a loop such as
75. intf Followed by ENTER n n sw getchar 0 if sw are me open file for read only fp fopenis w open file for write only while c getchar n Null statement to clear input buffer if fpe 0 fopen returns 0 if error printf nFile error n while fp 0 printf nPress n0 For Unix nl For CP M n printf nend of file marker then press ENTER n n HiSoft ZX C User Manual Page 11 c getchar 0 if c determine end of file marker al ial else ueof UNIXEOF while cegetchar n Null statement to clear input buffer if sw sandfile fp ueot send file down line else readfile ip weet read file from line fclose fp close file sendfile fp ecfu the definition of sendfile int fp eofu i int c printf nSending n while c getc fp E0F read a character at a time until EOF Pute c 4 print character to RS 232 puts eofu 4 finish with and of file marker princf nFile sent n the end readfile fp eofu the definition of readfile int p eofu int c printf nReading n while cegetc 4 eofu read a character at a time until end if c 0 of file marker is received IF character is not zero then send to file Putcic fp ig c n convert line feeds to carriage returns c r Putchar c echo on
76. is line is the terminating condition of a do while loop and unlike simple while loops there must be a semi colon after the while condition So we must edit this line Use the E command to edit the line as before but rather than stepping along the line press X The cursor jumps straight to the end of the line and automatically enters INSERT sub mode This is indicated by the cursor turning into a flashing We can now insert characters at the end of the line so type In a semi colon and press ENTER twice to get back to the main editor Compile the program again This time It stops at line 350 with error 0 missing Why Well this is a very obscure bug that frequently catches programmers out especially if they are used to other languages like Pascal It stems from the define statement on line 30 define allows macros to be used in C programs In this context a macro is any amount or text from the first separator after the identifier up to the next end of line marker Whenever the identifier is used in the program It is substituted for the entire macro text This means that whenever we use EOF it is replaced by the rest of the line 1 This is where the problem lies the semi colon after the 1 is confusing the compiler It shouldn t be there So we ll have to edit it out HiSoft ZX C User Manual Page 21 We re going to demonstrate a technique which is not at first sight the most obvious way to do the editing but it is the quickest
77. l ERROR 58 There is no error 58 ERROR 59 There is no error 59 ERROR 60 LIMIT no more memory The compiler uses the free space between the top of Itself and the end of free memory RAMTOP to keep many things The editors text is kept here and the compiled machine code of your program and the text of the error messages and workspace for the compiler This space is now all full You can make some room in Several ways use the error control line to discard the error messages save your program to tape microdrive etc and use Include file compile the entire program and run it rather than using direct simplify your program HiSoft ZX C User Manual page 63 ERROR 61 RESTRICTION use assignment or move to Initialize automatics The compiler does not support initialization of automatic local variables You should simply use an assignment statement instead Please note that you can initialize static local variables and these should normally be used in preference to automatics except where the function is recursive or re entrant To initialize large objects like arrays you can also act up a static array with the required data and then use the built in move function to copy the data into the automatic variable Note that you cannot initialize automatic arrays or structures within C and this is not a RESTRICTION ERROR 62 Cannot initialize this disallowed storage class You cannot initialize names of types structure
78. lock is a normal Spectrum header The data blocks are each 514 bytes long comprised of a character count in the first two bytes and up to 512 characters in the remainder of the block The top bit of the character count is set to indicate the last block in the file Normal Spectrum CODE files are used on Microdrive except that a start address andlength of 0 are used This means that most of the extended cataloging programs available for the ZX Spectrum Microdrives will return a file length of zero The compiler and compiled programs can open any type of Microdrive file for reading This is done automatically Function Linkage and the Stack The Z80 processor stack SP is used for function linkage and local variables The caller evaluates each argument in left to right order and pushes them on thestack in turn before calling a function so the last argument is on the top of thestack There must exactly as many arguments as the function expects The caller then enters the function with a CALL instruction to the start of the function The called function then takes over and it first pushes the IX register on the stack and loads IX with the current value of the stack pointer SP Space is then allocated for any automatic local variables by decrementing SP The function now executes using IX to access the arguments and its locals Finally it recovers the previous value of IX for the caller salvages the return link and discards the local varia
79. m without using cassette or Microdrive except when you want to save the program This means that you can type in a program using the editor then compile it and test its returning to the editor to correct it and add more features until your whole program is finished The editor keeps the text of your program in memory and allows you to add more or change what is there or delete some The compiler can then read and compile the text by Include The editor can also put the text onto cassette or Microdrive by p and reed it back by g The compiler is also able to read these files directly from tape or MICRODRIVE by Include filename In order to start using the editor when you are already using the compiler you should press cap shift and 1 simultaneously followed by the ENTER key or edit on the Spectrum and 128K machines You will see a vertical block when you press the EDIT key and the message edit when you press the ENTER key followed by the editor prompt gt There is a special way of entering the editor after an error message has been printed which makes it easier to correct mistakes After the compiler has printed the error message it stops and waits for you to press a key If you press the EDIT key then the editor will perform an E command edit line on the last line compiled You can make a correction immediately and carry on You will go back to the compiler if you press any other key after an error message In respo
80. many other arguments there were The standard library functions min and max make use of this faculty and the source code in the library HEADER file stdio h provides anexample of how to write such a function 10 2 External data definitions 11 Scope rules In HiSoft C an entire program is compiled at once so that there is no linkage of precompiled routines A source library facility is provided instead and this is described in section 12 2 11 1 Lexical scope Identifiers associated with ordinary variables and those associated with structure and union members and tags are not disjoint 11 2 Scope of externals 12 Compiler control lines 12 1 Token replacement Macro definition is limited to simple token replacement and no arguments are permitted undef control lines are not implemented See the Preprocessor section or details of allowed commands 12 2 File inclusion Files may be included the named file is searched for on the current device so thetwo forms are identical The or lt gt brackets may be omitted So the following control lines are all equivalent include filename include lt filename gt include filename In addition a library search facility is provided A control line include filename HiSoft ZX C User Manual Page 29 causes the named file is to read and searched The file should consist of a sequence of external function definitions Each function will be compiled only if it has already been called in
81. ms because scanf tries to match against a u character fails and gives up early which leaves junk in the remainder of the input variables Int fscanf fp control arg1 arg2 FILE fp char control This function behaves just like scanf except that its input is obtained from the file attached to fp rather than stdin Int sscanf s control arg1 arg2 char s char control This function behaves just like scanf except that it uses the string pointed to by s as its source of input Raw Level I O Functions Int rawin Inputs a character directly from the keyboard with no conversion of character codes There is no cursor and nothing is echoed to the display This function is intended for special applications such as games It waits for bit 5 of the FLAGS system variable tobe set then reads LAST_K and resets the flag This function is built in HiSoft ZX C User Manual Page 51 Intkeyhit Tells whether a key has been pressed an the keyboards returning TRUE 1 if so and FALSE 0 if not The function does not read the key and if it returns TRUE then youmust read the keyboard using rowin perhaps to get the key and reset the keyboard before you try to use keyhit again if you do not it will continue to return TRUE everytime The function uses the ROM KEY_SCAN routine This function is built in Port I O Int inp port_number Returns the 8 bit input value from the I O port specified by the 16 bit port_number
82. n value is NULL 0 void fputs s fp char s FILE fp Outputs the string s to the file pointer fp char gets s char get s Reads string s from the standard input the keyboard It is similar to fgets except that It has no maximum character count and also the newline character is overwritten by the terminating 0 Page 48 HiSoft ZX C User Manual void puts s char s Outputs the string s to the standard output the display with a newline at the end of the string void printf control arg1 arg2 char control This is the most important output function as it is used for almost all kinds of printing text numbers characters strings etc printf converts formats and prints its arguments on the standard output stdout under control of the string control It behaves as described in Kernighan amp Ritchie The control string is printed files it stands except that all conversion specifications in it are used to print the other arguments A conversion specification starts with a character then follow some optional modifiers and finally the conversion character All the conversion specifications are supported except the floating point ones signed decimal number unsigned octal number unsigned hexadecimal number unsigned decimal number e g store address a single character a string terminated bya O character naOcoCKOa The character specification modifiers are also all supported left justify field
83. nest majority of our customers for belaboring this point Nuff said would now like to make our own acknowledgment to Leor Zolman at BD Software This compiler was originally written entirely in BDS C and a good C it is It has been rewritten in assembler to achieve the size but there are still a few C functions left in there The runtime support for those functions is copyright of Leor Zolman The functions themselves are copyright of HiSoft Example Programs To demonstrate a few of the more basic techniques of C programming to the beginner we have produced a few short example programs here which may be typed In compiled and executed or simply examined for reference You may find stunt of the functions and techniques used may come in handy In more complex applications The Sieve of Eratosthenes This program uses the famous algorithm known as the Sieve of Eratosthenes to calculate all the prime numbers up to 3190 If you wrote a similar program In Spectrum BASIC you would be pleased at the dramatic speed Increase offered by C The listing of the Sieve program is on the next page SIEVE BENCHMARK from June 84 BYTE compute primes using Sieve of Erastosthenes define NTIMES 10 number of times to run sieve define SIZE 8190 size of number array define FALSE 0 define TRUE 1 char flag SIZE 1 main int i j k count prime printf d iterations NTIMES for i l i lt NTIMES i I
84. ng ch Behaves like strchr except that it returns the last occurrence of ch in string ratherthan the first Storage Allocation and Freeing Heap Management These functions are explained in detail In Kernighan amp Ritchie Note that there is a small control region allocated in stdio h for use by these functions it is the head of the free store chain char calloc n size unsigned n size Allocate apace for n items of size bytes each It returns a pointer to the start of the apace or else it returns NULL if there is no space For example p calloc 100 sizeof int allocates 200 bytes enough for an array of 100 Integers There are actually some more bytes hidden before the block which are used by free when the block is finishedwith These hidden bytes must not be changed The function corresponds to new in Pascal and zeros the store for you char malloc n unsigned n Allocate n bytes of memory It returns a pointer like but it does not zero the store void free block char block Return a block of store to the free store chain for re allocation later by calloc You must return a copy of the pointer supplied by calloc when the storage was obtained and the hidden bytes must be intact The function corresponds to dispose In Pascal char sbrk n unsigned c This is another function associated with storage allocation and the reasons for its existence are a little obscure What it does is to allocate n bytes of
85. nse to the prompt you may enter a command line of the following format C N1 N2 1 S2 followed by ENTER for example to replace fred by tom in lines 1 50 of the file you would type FI 50 fred tom ENTER C Is the command to be executed N1 Is a number in the range 1 32767 inclusive N2 Is a number in the range 1 32767 inclusive S1 is a string of characters with a maximum length of 20 S2 is a string of characters with a maximum length of 20 Very few of the editor commands need or expect all five pans of a command line and in some cases most would be inappropriate anyway To return to the C compiler you should type C followed by ENTER You can also exit to BASIC by typing B followed by ENTER The editor uses line numbers in many of the commands These line numbers are only used by the editor and are not stored in files on cassette or Microdrive nor are they used by the compiler Lines are given numbers automatically by the editor when it reads them from tape or when you type them in with the command It is therefore best to regard these line numbers as notional provided only for your benefit when using the editor HiSoft ZX C User Manual Page 15 The comma is used to separate the various arguments although this can be changed see the S command and spaces are ignored except within the strings None of the arguments are mandatory although some of the commands e g the Delete command will not proceed without N1 and
86. o prevent some errors by insisting on the types being correct Page 64 HiSoft ZX C User Manual Passing the wrong number of arguments to a function when it is called This may cause a crash by using the value of an argument that wasn t there or by unbalancing the slack when the function returns C doesn t check the number of arguments Calling a pointer to function variable e g int ptr_to_func which has a bad value or hasn t been initialized This is just a random jump Calling a function which hasn t been defined in direct mode Of course the bad values in these cases may not be obvious they might be caused by any of the errors listed below Now for a general list of likely problems Capital letters are different to lower case letters in identifiers Check that all comments are terminated Check that all string constants are terminated Check that all variables are initialized particularly that a pointer points where it is supposed to before using it to store through i e don t write ptr x before writing ptr y Check carefully that is used for equality tests and only for assignment Remember that all arrays start from Index 0 An array declared as a N has just N elements going from index 0 to index N 1 An array name evaluates to a pointer to the array and in particular does not cause a copy of the array to be passed to a function There are no complete array or structure assignments It must be done elem
87. ognizes that the result of an operator is constant when all its operands are But it does not rearrange expressions so that while it will partially evaluate 2 i at compile time leaving 3 i to be calculated at run time it will not evaluate any of i 1 2 but will calculate i 1 2 at run time The compiler accepts as a case constant or as an array hound or as an inline any expression which it recognizes as a constant expression 16 Portability considerations Function arguments are evaluated left to right Character constants can only be a single character The characters in a string are allocated in order of increasing memory address as are the elements of an array You are urged not to rely on unspecified features except where absolutely necessary Details of many implementation considerations are given to increase understanding and for those uses where it is essential But that is not an invitation to rely on them For example it is stated above that function arguments are evaluated left to right they may not be in the next version of the compiler 17 Anachronisms The compiler does not support these Anachronisms The Compiler Preprocessor This section gives details of the preprocessor part of the HiSoft C compiler A preprocessor command is one which is preceded by a sign The preprocessor interface is not as clearly defined as the language itself as different systems have different requirements The commands cur
88. or less than two arguments are specified then no action will be taken this is to help prevent careless mistakes a single line may be deleted by typing dm m enter A single line can also be deleted by typing just its line number followed by ENTER MOVE LINE Command Mm n This causes the text at line m to he entered at line n deleting any text that already exist there Note that line m is left alone So this command allows you to move a lineof text to another position within the textile If line number m does not exist then no action is taken RENUMBER TEXT Command N lt m n gt Use of the N command causes the entire text file to be renumbered with a first linenumber of m and in line number steps of n Both m and n must be present and if the renumbering would cause any line number to exceed 32767 then the original numbering is retained EDIT LINE Command En Edit the line with line number n If n does not exist then no action is taken otherwise the line is displayed on the screen with the line number and the line number is displayed again underneath the line The cursor appears after this line number and the special editing commands can then be used to edit the line gt CAPS SHIFT 8 not symbol shift E step along to the next character on the line You cannot step beyond the end of the line lt CAPS SHIFT 5 not symbol SHIFT Q step back to the previous character on the line You cannot step backwards beyond the
89. ow type g stdio h ENTER The border will turn red to warn you that the compiler is going to use the tape Press PLAY on the tape recorder now You will see the border flashing as the compiler reads in the function library header Press STOP when the cursor reappears and the border Stops flashing because there is another file on this side of the cassette Now save the header by typing pl 9999 stdio h ENTER to save to cassette have a blank One ready or pl 9999 1stdio n ENTER to save to Microdrive 1 HiSoft ZX C User Manual Page 7 Wait until the cursor reappears again Now we will repeat this process to save the library itself but first we need to clear the editors buffer so that there is room Type dl 9999 ENTER Now read the cassette file g stdio lib ENTER Press PLAY and wait for the library to be loaded Now save it by typing pl 9999 stdio lib ENTER to cassette or pl 9999 1 stdio lib ENTER to Microdrive and wait for the cursor again That s it Keep the original tape that we supply since you will need it for any upgrades Making a Backup on the Plus 3 Before using HiSoft C please make a backup don t use your master disc if you destroy your master disc we will have to charge you for re recording It First format a disk using FORMAT A and then copy the files using COPY A X B with the master disc in the drive and you will be prompted to swap discs when necessary Now you can put th
90. perator in an expression about what types of operands it can take and somewhere in this expression those rules have been broken The compiler displays the error message as soon as it can but it has to evaluate the operands before it knows their types and can check them Details of the combinations which are allowed are In section 7 Expressions in the C Reference Manual This message refers to a binary or ternary operator e g or ERROR 33 bad operand type Similar to the previous error but this refers to the operand or a unary operator such as amp etc ERROR 34 need an _ ivalue Some operators can only take arguments which are ivalue e g The rules about when an operator needs an ivalue and what an ivalue is are given in the C Reference Manual but roughly speaking an ivalue is a memory address which can be stored into Remember in particular that an array name and a function name are not lvalues ERROR 35 not a defined member of a structure Only structure or union member names can appear on the right of a gt or a operator ERROR 36 expecting a primary here The compiler is looking for a primary such as a variable name in an expression This is another error that can be confusing because it is really a negative statement The compiler believes it is in a function body so expressions are allowed and has decided that the current input is not a declaration or a specific statement e g while or if so i
91. physical memory for use by calloc It is not normally called from anywhere else HiSoft ZX C User Manual Page 45 Why is this extra function necessary when calloc could do it directly Well it allows you to decide which area of memory should be used to provide the space for the heap On Unix and many other larger systems sbrk calls the operating system which makes memory available by moving things around or by taking it from another user etc etc On the Spectrum it is up to you to decide an a safe area of memory to be used There are several possible places to get the memory and we have included an sbrk function which uses the safest of these You can rewrite it if you want to use one of the other places The main possible places are 1 A static variable created just for this purpose This is the safe option we have chosen it does restrict the amount of memory available for your program but only if you actually call calloc 2 Above RAM TOP Move RAM TOP down with a CLEAR nnnnn before starting the C compiler and this will provide a safe area of memory 3 Below 25200 If you are not going to use two files You will have to work out where the safe area is The cassette uses an area from 24512 to just below 25200 Miscellaneous Functions void swap p q length char p q unsigned length 1 This function swaps the contents of two areas of store each length bytes long and pointed to by p and q It is used by qsort in
92. putchar c These correspond to getc 0 and putc c 0 respectively Before using putc or getc you must make sure that you have a file pointer You can use 0 as a file pointer for the display and keyboard as mentioned above You can also use streams 1 for the keyboard lower screen 2 for the upper screen and 3 for the printer For cassette and Microdrive you must call fopen as described below to get the file pointer The file pointer for cassette will be a special one 16 For Microdrive it will be the highest unopened stream number i e normally 15 and if that is already open then 14 In addition you can open streams in some other way from BASIC or by a machine code routine and then just pass the stream number to getc or putc Do not try this with cassette or Microdrive because the I O system will get very confused All input and output on cassette at Microdrive both referred to as tape is done by programs at character level using the functions getc fp and putc c fp The characters are collected into blocks by the C runtime functions before being put on the tape in a file The input and output done by the compiler is done in the same way as by user programs so you can create or read C source files Before reading from or writing to tape it is necessary to call the standard library routine fopen filename mode On output this constructs a header block and writes it to tape whilst on input it searches the tape for a matching h
93. rently supported in the ZX Spectrum implementation of HiSoft C are as follows HiSoft ZX C User Manual Page 33 define lt identifier gt lt macro gt This command allows for limited macro expansion and is the means by whichconstants are defined in C programs The test following the define command is normally a name which we would choose to use in place of a number or expression such as EOF rather than 1 This is the lt identifier gt part of the command The lt macro gt pact is the text with which the identifier is to be replaced whenever it is used in the main program For example if we had the following preprocessor commands at the head of a program define EOF 1 define maximum 1000 then whenever we used EOF or maximum in the program they would be replaced by 1 and 1000 respectively Remember that the whole of the text following the lt identifier gt is used in the replacement so the very common error of putting a semi colon after the lt macro gt part should be taken particular notice of K we had typed define EOF 1 then every occurrence of EOF would be replaced by 1 which is not normally what isrequired Kernighan and Ritchie allow define macros with arguments so if aprogram is transferred from another compiler any macros with arguments should be rewritten as functions This implementation does not support define macro arguments and the undef preprocessor command to make the compiler forget an earlier define macro
94. ribute them on low priced library cassettes so that they can be made widely available Some of these library functions may also be distributed in stdio lib with the compiler An up to date copy of the library will be sent to everybody whose functions are included in the library If you wish to contribute to the library please send a cassette containing the C source of your functions and the documentation for them because we don t have enough time to type it all in Ideally send a printed copy as well Put your name into the documentation and as a comment in the source You can put your address as well if you are happy to get comments from other users Arithmetic functions Int max n auto Returns the value of the greatest of its integer arguments The function takes any number of arguments it is variadic HiSoft ZX C User Manual Page39 Int min n auto Returns the value of the smallest of its integer arguments The function takes any number of arguments it is variadic NB min and max are in stdio h because they are variadic Int abs n Returns the absolute value of its argument Int sign n Returns 1 if the argument is less than zero 0 If the argument is zero and 1 if the argument is greater than zero An Illustration of How to Grub Around in the Store peek and poke are provided to show how to access absolute locations in store from Cprograms It is often possible to write specific functions for a particular p
95. rogram which are more efficient and easier to use A useful technique is to define a C structure which represents the layout of the piece of store being used and then assign the address of the store area to a pointer to the structure These routines do this for the simple case of a single byte Typedef char _char_ptr char peek address Returns the value of the byte of store at location address Void poke address value Puts the low eight bits of value into store at location address Note that the function has no result which is denoted by the void type Format conversion routine ASCII to binary Integer Int atol s char s Scans the string s and returns the binary value of the ASCII number in it The function first scans over any white space space tab or NEWLINE characters and thenconverts the number The conversion stops when it finds the first non digit character The value 0 is returned if no number is found The number may have a or a sign in front of it Page 40 HiSoft ZX C User Manual Sorting function a Shell sort void qsort list num_items size cmp_func char list int num_items size int cmp_func Sorts a list of items into ascending order using a Shell sort The Function is called qsort because the Unix original used Hoare s quicksort The items are all the same size size bytes long There are num_items of them They appear one after the otherstarting the list cmp_func is a pointer to
96. s etc as opposed to variables of these types ERROR 63 Cannot Initialize this disallowed type It is not permitted to initialize variables which are unions functions etc ERROR 64 too much Initialization data There are more constants m the initializer list than are needed to initialize the variable ERROR 65 bad Initializer need a Initializers for structures and for arrays must be enclosed in curly braces even if they are only a single constant Common Mistakes In C Programs C is intended to be a systems programming Language and is designed first and foremost to provide power to the user without runtime overheads Because of this there are numerous ways to make mistakes in C programs and these can have startling effects particularly if you are used to the protection of languages like Pascal Debugging C is more like debugging assembler save your source text before running a compiled program This section lists some likely causes of programs that don t work concentrating on those that won t show up immediately as error messages when the program is compiled First the disasters crashes and what to look for Using an array index with a bad subscript and so storing into an arbitrary location Note that C does not have subscript checking Assigning a bad value to a pointer and then using it to store a value or Incrementing a pointer past the region it should point to Very similar to the array errors HiSoft C tries t
97. s this will be quite acceptable but there are instances when it would preferable if the program could run by itself without the need to load the compiler and compile the program before using it If for example one were producing a product intended for commercial sale It would not be very useful unless it had the ability to run by itself translate gives it this power and the resultant file is a machine code program which can be loaded and run by the normal use of load filename code and RANDOMIZE USR 25200 instruction Other Preprocessor Commands Although Kernighan and Ritchie mentions a few other preprocessor commands such as line and undef they are not supported in this compiler in most cases this is because they are not needed in the environment which the compiler produces Explanatory Notes These notes are provided to explain and motivate particular aspects of the C programming language or of the HiSoft C compiler Type Checking Variables in C programs are each of a particular type which may be one of the predefined types or a user defined type declared with a typedef declaration or ananonymous type e g int f 1 The C compiler checks that the variables used in an expression are of compatible types in order to help detect programming errors In C this checking is by a method known as structural equivalence This means that two variables have the same type if their declarations have the same structure no matter where th
98. standard Input stdin This function does buffered input from the keyboard Incoming characters are collected into a line bullet until ENTER is pressed Hit delete key can be used to edit the characters as they are typed A flashing cursor is displayed and characters are echoed on the display as they are typed This function is built in Int putchar c int c Put a character to the standard output stdout The character is displayed on the screen The function returns the character as its result also This function is built in Complex level I O Functions void exit n This function is a mixture of I O function and system function It closes all files which the program has open and then exits from the program by calling exit see below The parameter n is passed out as the result of the program and it is used to indicate whether or not the program was successful A return value of 0 means success other values indicate an error by causing the corresponding Spectrum error report to be displayed char fgets s n fp char s int n FILE fp Head string s from file pointer fp The reading will stop when a NEWLINE character is read or when n 1 characters have been read whichever occurs first So n is the size of s The string will be terminated by a a character which is added after the newline character The return value is normally s but if the end of file has already been reached when fgets is called then the retur
99. storage is used for global external variables and for all static variables This storage is allocated starting at the top of memory at RAM TOP and working downwards The stack is below the static storage and is moved down when necessary to keep it so Static storage is accessed directly by addresses in the compiled instructions Automatic storage is used for automatic local variables arguments and function linkage and temporary working store It is allocated on the stack and accessed usingSP and IX Storage for individual variables is allocated in the same way regardless of whetherautomatic or static storage is used First is storage for the basic types then for derived types char 1 byte int 2 bytes least significant byte at lower address unsigned 2 bytes least significant byte at lower address pointer 2 bytes least significant byte at lower address Contains address of pointed to object array n s bytes where n is the array bound and s is the size or each element The first element a 0 is at the lowest address A multi dimensional array such as a m n is treated as an array with bound m of arrays with bound n of the elements So in the case ofa character array element ali j is at address ati n j structure s bytes where s is the sum of the sizes of all the members of the structure The first member of the structure to be declared is at the lowest address as described in Kernighan amp Ritchie union s bytes where s is
100. t an attempt to invoke a non existent function results in a jump to a random location which almost certainly means that the machine will crash and the compiler will have to be reloaded include This command is probably most usefully seen as a command to initiate compilation although its more precise effect is to include a specified file in the compilation of another It has three major forms as below include This compiles the program held as source text in the integral editors memory space This program may itself contain further include directives but they will not be ofthis type include filename or include filename or include lt filename gt This command causes the named file to be included in the current compilation which may mean that the named file alone is compiled if it is issued as a stand alone command If the command forms part of another file then the named file will be included in the compilation of the calling file A file included in the compilation of another may not itself contain further include directives All three forms given above are equivalent include filename This variation of the command allows for library file inclusion In many respects italso gives the user a conditional compilation capability as it only compiles those functions in the named file which have been used somewhere in the main files The command would normally be the last instruction in a file and its effect is to scan throu
101. t must be an expression It has further decided that the current input is not an operator and so it must be a primary One particularly obscure case which can cause this message sometimes is an unclosed comment if you think through it when it happens you can probably understand why Page 60 HiSoft ZX C User Manual ERROR 37 undefined variable The name of an undefined variable has been used in an expression Define it as a global or at the top of the function ERROR 38 need a type name The sizeof and the cast operators will only work on the name of a type either one of the basic types e g unsigned int or one declared using typedef They won t accept an anonymous type such as int DIJ and the sizeof operator won t accept a variable name because you can write the program with named types more clearly and help keep the compiler small ERROR 39 need a constant expression The compiler will accept and evaluate any constant expression here but it has just encountered something which isn t constant ERROR 40 can only call functions A left parenthesis after a variable name looks like an attempt to call that variable as a function and to do that the variable must be declared as a function returning something Maybe there is a missing or some such between the variable and the parenthesis or a missing indirection in front of the variable ERROR 41 does not follow a properly The compiler has found a colon
102. t recommend running the compiler using Loader from the menu since if you attempt to exit to BASIC for any reason you are returned to the Loader rather than BASIC The 3 version uses standard 3DOS filenames the use of drive letters is optional Thus for example p1 9999 test c will save the current program as test c on the current drive normally A but you can use say g m myprog c To load a file from drive M The same names are used by both the compiler for include and translate and also by the library in the fopen routine Note that you cannot use cassette directly from the compiler but see below for how to convent tape source programs to disc General After loading in the above way the compiler will be executed automatically and will produce its sign on message HiSoft C Compiler v1r3 copyright c 1984 HiSoft Alter the sign on message you will see a flashing cursor and you can now type a C program Try a short one using SYMBOL SHIFT F for and SYMBOL SHIFT G for main printf Hello world Now type SYMBOL SHIFT for End Of File and the compiler will ask your Type y to run program Page 4 HiSoft ZX C User Manual Type y and you will set the program run and prompt you again You can rerun the program any number of times by typing y but this time Just press ENTER and it will then go back to its sign on message hello world Type y to run program HiSoft C compiler v1 3 Copyright c 1984 HiSoft
103. the tape or if the cassette is damaged just get in touch with us and we will exchange it for an identical working copy Compare this with the guarantee that you get with your copy of Kernighan amp Ritchie or with your Spectrum There are two sorts of copy which you might wish to make and we give details here You may want to copy the function library so that you can change the functions or add new ones and if you have Microdrives then you may well want a working copy on Microdrive The compiler will automatically ask you whether you want to make a working copy on Microdrive when you first load it from tape Make sure that you have a formatted cartridge in Microdrive 1 and answer y to its question The compiler will save itself onto Microdrive and then start up You will see its sign on message When you want is reload the compiler from Microdrive you can do so by typing LOAD m 1 cc or LOAD m 2 cc etc The function library is supplied as a normal C source text file and you can use the compiler itself to make a copy The function library comes in two parts the header and the library proper We start by making a copy of the header Press EDIT CAPS SHIFT and I and then ENTER You will now see the message edit and the editor prompt gt We are going to read the library into the editors buffer and write it out again so at this stage turn the cassette over so that the label which says Library is uppermost and rewind the cassette N
104. tion can appear again in the declarations before the start of the function body ERROR 27 undefined variable s At the end of compiling a program the compiler checks that all the variables used in the program have been properly defined and it lists any which have not These are usually functions and if they are all library functions they can now be conditionally included by using a library search This error does not restart the compiler You can carry on and type more input to the compiler afterwards such as include ERROR 28 bad function return type There are some restrictions in C on the types which a function may return as its value The details are given in section 8 4 The Meaning of Declarators of the C Reference Manual in Kernighan amp Ritchie HiSoft ZX C User Manual Page 59 ERROR 29 no arrays of functions But it is possible to have arrays of pointers to functions Perhaps that is what is needed ERROR 30 LIMIT expression too complicated too many arguments The intention is that this limit won t be reached in normal use if it is break up the expression by an intermediate assignment or rearrange it with fewer parentheses ERROR 31 LIMIT expression too complicated too many operators The intention is that this limit won t be reached in normal use if it is break up the expression by an intermediate assignment or rearrange it with fewer parentheses ERROR 32 bad type combination There are rules for each o
105. to keep the compiler as small as possible means that to people looking at the whole program the message may seem strange For example if you write f a b then the compiler will say missing after the a The explanation is lengthy but straightforward the compiler knows it is compiling a function argument list and starts compiling the first argument expression a It then reads the next token b and decides that the first argument has now finished because two variables cannot be adjacent in an expression they must have a or some other operator between them Now if there are more arguments in the list then there ought to be a comma next and clearly there isn t so the compiler decides that it must have reached the end of the argument HsL At the end of the argument list there must be a but instead there is ab The compiler generates the missing message ERROR 1 RESTRICTION floats not implemented Sorry ERROR 2 bad character constant The compiler didn t find the closing Check the syntax in the Language Reference chapter and in Kernighan amp Ritchie ERROR 3 nota preprocessor command This line looks like a preprocessor command it starts with a but it isn t one that the compiler recognizes Check in the Language Reference chapter Page 66 HiSoft ZX C User Manual ERROR 4 LIMIT macro buffer full The intention is that this limit won t be reached in normal use The compiler has a buffer where it remembers the def
106. to use default values to check thatthese values are correct The command also displays the start and end address of the text file in decimal Thisis useful if you wish to save the tent from within BASIC or if you want to see how much memory you have left after the text file SET DELIMITER Command S d This command allows you to change the delimiter which is taken as separating the arguments in the command line On entry to the editor the comma is taken as the delimiter this may be changed by the use of the S command to the first character ofthe specified string d Remember that once you have defined a new delimiter it must be used even within the S command until another one is specified Use V to discover the current delimiter Note that the delimiter may not be a space RETURN TO THE C COMPILER Command C When you have finished editing the text and want to compile it Just type C and press ENTER RETURN TO BASIC Command B You can return to BASIC by typing B and ENTER This can be useful if you want to open or close a stream to the serial channel for example or load or save some data To re enter the C compiler afterwards type RANDOMIZE USR 25200 ENTER If you don t want to came back but want instead to use BASIC you will have to reset the Spectrum or see the low level Interface HiSoft ZX C User Manual Page 17 DELETE LINES Command D m n All lines from m to n inclusive are deleted from the text file If m gt n
107. turns TRUE if the character is ASCII i e less than 0x80 Int Iscntrl c char c Returns TRUE if the character is a control character Int Isdigit c char c Returns TRUE if the character is a digit This function is built in Int islower c char C Returns TRUE if the character is a lower case letter a z This function is built in Int Isprint c char c Returns TRUE if the character is a printing one Int ispunct c char c Returns TRUE if the character is punctuation i e printable and not a letter or a digit Int isspace c char c Returns TRUE if the character is whitespace That is if it is the space character the NEWLINE character or the tab character This function is built in int isupper c char c Returns TRUE if the character is an upper case letter A Z This function is built in char tolower c char c If the character is an upper case letter then it returns its lower case equivalent and otherwise it returns the character unchanged This function is built in HiSoft ZX C User Manual Page 43 char toupper c char c If the character is a lower case letter then it returns its upper case equivalent otherwise it returns the character unchanged This function is built in Int Isgraph c char c returns TRUE if c is a graphic printing character greater that space and less than 0x7f Intisxdigit c char c Returns TRUE if the character is a hexadecimal digit 0 9 a f A F
108. ual LIST TEXT ON THE DISPLAY Command I m n This lists the current text to the display from line number m to Line number ninclusive The default value for m is always 1 and the default value for n is always 32767 i e default values are not taken from previously entered arguments To list the entire textile simply use L without any arguments After listing a number of lines the list will pause and you can press EDIT to stop the listing early or press any other key to continue the listing The number of screen lines listed on the display at once may be controlled by the K command below LIST LENGTH CONTROL Command K n K sets the number of screen lines to be listed to the display before the display is paused as described in L above For example use K5 if you wish a subsequent list to produce five screen lines at a time The editor starts off with a K value often The K value cannot be greater than 255 WRITE TEXT TO PRINTER Command W m n The W command causes the section of text between lines m and n inclusive to belisted on the printer If both m and n are defaulted then the whole text file will be printed You may hit the break key CAPS shift and Space to abort the printing and return to the editor VIEW DEFAULTS Command V The V command displays the current delimiter and the current values of the twodefault line numbers and the default strings N1 N2 S1 and S2 This is useful beforeentering any command in which you are going
109. white space in the equivalent position in the input stream Any amount is from zero to an indefinite maximum Ordinary characters not which must match the next input character Conversion specifications consisting of the character an optional assignment Suppression character an optional number specifying a maximum field width and a conversion character A conversion specification determines how the next input field is interpreted Normally the result is placed in the variable pointed to by the corresponding argument This means that the argument usually starts with an operator if assignment suppression is selected by the character then the input field is simply skipped and no assignment is made An input field is defined as a string of non white space characters it extends either to the next white space character or until the field width if specified is exhausted Hence ENTER the TAB character or SPACE can be used to separate input fields to scanf Note however that unlike the scanf described in Kernighan amp Ritchie white space in the Input field will only be accepted when it matches a white space character in the control string This is so that a control stung say alpha will not match an input string with embedded space say alpha This was an oversight which made the original scanf act rather unintelligently in certain circumstances but later versions of Unix C follow the same form as we have here The conversion
110. written as for i O i lt n i do_something Remember that incrementing a pointer causes its binary value to be increased by the size of the object That it points to so that ii points to the next object in an array In particular remember that pointers to int increase by two bytes at a time Remember also that any value added to a pointer will be multiplied by the size of the object first Arithmetic overflow is not an error and is not tested for This can be useful sometimes but means that you must include explicit checks if you need them A string is a pointer to an array of char i e an address You cannot use Pascal like tests of equality on strings In particular beware of typing x when you mean X The first is the address of a two byte array the second is the ASCII value of a character A string has a zero byte on the end Remember that when calculating array lengths and remember to put one there if your program makes strings The precedence of operators can be surprising at times Check the relational operations lt etc and remember that shift operators are of lower precedence than addition so that hi lt lt 8 lo doesn t mean what it seems to The order of evaluation of an expression is not specified and must never be relied on An else belongs to the immediately preceding if Execution flows through case statements into the next one A break is needed is exit from the switch statement if a switch variable do

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