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1. 38 GNU MIX Development Kit mdk display mix cell string gt number car arglist newline and we can install them using mix add pre hook smem smem pre hook mix add post hook smem smem post hook Aferwards a sample execution of mix smem would look like this guile mix smem 2000 100 Changing address 2000 Old contents 0 New contents 100 guile gt You can add any number of hooks to a given command They will be executed in the same order as they are registered You can also define global post pre hooks which will be called before after any mixvm command is executed Global hook functions must admit two arguments namely a string naming the invoked command and a string list of its arguments and they are installed using the Scheme functions mix add global pre hook and mix add global post hook A simple example of global hook would be guile gt define pre hook lambda cmd args display cmd display invoked with arguments display args newline guile gt mix add global pre hook pre hook ok guile gt mix pmem 120 125 pmem invoked with arguments 120 125 0120 00 00 00 00 00 0000000000 0121 00 00 00 00 00 0000000000 0122 00 00 00 00 00 0000000000 0123 00 00 00 00 00 0000000000 0124 00 00 00 00 00 0000000000 0125 00 00 00 00 00 0000000000 guile gt Note that if you invoke mixvm commands within a global hook its associated command hooks will b
2. 00 00 0000 rli 00 00 0000 rI2 00 00 0000 rI3 00 00 0000 rI4 00 00 0000 Chapter 6 mixvm the MIX computer simulator 55 rI5 00 00 0000 rI6 00 00 0000 MIX gt As you can see in the above sample the contents is printed as the sign plus the values of the MIX bytes stored in the register and between parenthesis the decimal representation of its module pall prints the contents of all registers plus the comparison flag and overflow toggle Finally sreg Sets the contents of the given register to value expressed as a decimal constant If value exceeds the maximum value storable in the given register VALUE mod MAXIMU VALUE is stored e g MIX gt sreg I1 1000 MIX gt preg I1 rli 15 40 1000 MIX gt sreg I1 1000000 MIX gt preg I1 rli 09 00 0576 MIX gt p lags state command scmp El GITL state command sover F T state command pflags prints the value of the comparison flag and overflow toggle of the virtual pmem smem machine e g MIX gt pflags Overflow F Cmp E MIX gt The values of the overflow toggle are either F false or T true and for the compari son flag E G L equal greater lesser scmp and sover are setters of the comparison flag and overflow toggle values from to state command address value state command pmem prints the contents of memory cells in the address range FROM TO If the upper limit o is omitted only the co
3. tory the requirement section 4 to Preserve its Title section 1 will typically require changing the actual title TERMINATION You may not copy modify sublicense or distribute the Document except as expressly provided for under this License Any other attempt to copy modify sublicense or distribute the Document is void and will automatically terminate your rights under this License However parties who have received copies or rights from you under this License will not have their licenses terminated so long as such parties remain in full compliance FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new revised versions of the GNU Free Documentation License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns See http www gnu org copyleft Each version of the License is given a distinguishing version number If the Document specifies that a particular numbered version of this License or any later version applies to it you have the option of following the terms and conditions either of that specified version or of any later version that has been published not as a draft by the Free Software Foundation If the Document does not specify a version number of this License you may choose any version ever published not as a draft by the Free Software Foundation 92 GNU MIX Development Kit mdk ADDEND
4. ENT 14 LDAN Mr 12 ENTX nasum pec dRbflllle rcu 14 EI RK GENEE 12 E 20 EDIN oros tra ass 12 A A T EAT 62 LDR CO COn o ees 12 External programs csse 63 LDXN 223 t n eR dae ubt ew pe 12 load Re Ehre GREER ER end 49 E68 suopte PEEL EPI C PIN UE 61 H A nadie ge tic ERE eure de 48 M HET iesus cusa tais ea ed Pair pter RAN 18 96 miz add cond break o 68 mix add global post hook 68 mix add global pre hook 68 mizr add post hook eee sasse 68 Mix add pre hook EE 68 E Ll ivi cir a A E 70 EK anita da Ro Eben 70 MI ria EAT ETARE 71 MIX Eer EE 70 nix last resu lt i cz me e me EE RETE 67 o el A E EE E T TES 7O E Vii ve EET RU AA A 70 MIA PM cris ia e bees d 67 Ee eri o cage id 67 DEE DAME caia ecd yee werd 4 70 MIX prog PATO iii ee rr 70 DEE eg EEN 70 EE ria E 70 mix set col ii dr bee a 70 e AA EE 70 o de eebe X 34 REC Aue weds 70 e A Eed PE EPE EPE eee 70 MIX SOVER ae ies aa 68 Dnix Src lit 4 evI e EE ape eee uk aee 71 nix src lin no cvv e eorr ea Ee 71 WEE path ebe panei i bs 71 MIXTO E d 67 MUR Up CUMS a is 70 El break iii ad adas 69 mim Cond breakt 0 e eee eee 69 MUR VM OMPtY resarcir EELER s 69 nix vm err or 2 5sse ekan ek has iia 69 nix vm halted das rame c wks SE FS 69 nix vm loaded oen er na 69 mix vm running nerexes ese dee e gate es 69 nix vm Status isiese ekbnbnenzearRRku dy Rari 69 nixvm emnd siu exa nre ER RR ehe WS 66 nixvu
5. START EQU 2000 ORIG START NOP HLT END START which would give rise to the same compiled code Symbolic constants or symbols for short can also be implicitly defined placing them in the LABEL field of a MIXAL instruction in this case the assembler assigns to the symbol the value of the location counter before compiling the line Hence a third way of writing our trivial program is ORIG 2000 START NOP HLT END START The CON directive allows you to directly specify the contents of the memory address pointed by the location counter For instance when the assembler encounters the following code snippet ORIG 1150 CON 1823473 it will assign to the memory cell number 1150 the contents 00 06 61 11 49 which corre sponds to the decimal value 1823473 Finally the ALF directive let s you specify the memory contents as a set of five optionally quoted characters which are translated by the assembler to their byte values conforming in that way the binary word that is to be stored in the corresponding memory cell This directive comes in handy when you need to store printable messages in a memory address as in the following example OUT MSG MSG is not yet defined here future reference MSG ALF THIS MSG gets defined here ALF IS A ALF MESSA ALF GE D In the original MIXAL definition the ALF argument is not quoted You can write the operand as the ADDRESS field without quotes but in this case you must foll
6. Statusiie e e de ed Swe Ban eee mus 69 LIRE 18 Lu EE EEN 14 TOK EE 50 Next oues is 62 NEEN te eh eg ere det Ces Ze 18 Nee ege tga stants ee se uns et ee S tn Ke GNU MIX Development Kit mdk PP A dace Mee baat eager a 54 pddir lere neies c aedi ene ui pe aed pies 56 SL E EE 56 pilagsu sssb5 eteer seges ciu id 55 A eee are nee aS EN eens 52 EE 55 j RARO PE deientieegeseweseieae yes 49 PEEP m 54 EIERE geg pa os pa rte 57 PSEC Mir it li 49 petat iones 54 PSYM EE 51 ptime eee e xad ennn ker EGG d Pii 56 Q Quit olet dg e ew pepbrfiraekeqenr phepbehra 50 TUD hos ere RD en EUER Ae Se 49 Ree allah bt Abate were acda tack a lad at aewee 62 S cC PEPPER 56 AA ditt e rd 63 Save On exlt ewige Ru Ar IPS uides 63 le 50 Ge 51 Cj ED MP M 51 EP PTT 51 SDpE sj y erseneestel sq deleti Rare bid 51 SCUE soe EEEE oT A O dac che RR a etd 55 cista M 56 EE 56 NJ ENEE Lini SAX EE EE 1T Eege EE 17 SLOP ici land is adios REP PEE 56 SMM seis dis tunes te e DC Aen 55 CEET 55 PDA a Ai 50 GIE I7 GIE Tr EEEE emetad Ahineeagie ecthenats 17 EE 54 E Moira aa papa 53 Rug MEE 13 yb prm 13 Ee e KEE 56 TASA d 13 SUDdCO 2 EE eege dE Se eI Id EE 51 hus dem 13 SEELEN 18 SUB ei uev eee ta deu Rs 14 SynbOlS i 22 28 cra bar 62 Instructions and commands T Toolbar s ie rata Di ep Pes 97
7. Version Only one passage of Front Cover Text and one of Back Cover Text may be added by or through arrangements made by any one entity If the Document already includes a cover text for the same cover previously added by you or by arrangement made by the same entity you are acting on behalf of you may not add another but you may replace the old one on explicit permission from the previous publisher that added the old one The author s and publisher s of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version COMBINING DOCUMENTS You may combine the Document with other documents released under this License under the terms defined in section 4 above for modified versions provided that you include in the combination all of the Invariant Sections of all of the original documents unmodified and list them all as Invariant Sections of your combined work in its license notice and that you preserve all their Warranty Disclaimers The combined work need only contain one copy of this License and multiple identical Invariant Sections may be replaced with a single copy If there are multiple Invariant Sections with the same name but different contents make the title of each such section unique by adding at the end of it in parentheses the name of the original author or publisher of that section if known or else a unique number Make the same adjustmen
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11. 1T GNU MIX Development Kit mdk The terms of this License will continue to apply to the part which is the covered work but the special requirements of the GNU Affero General Public License section 13 concerning interaction through a network will apply to the combination as such Revised Versions of this License The Free Software Foundation may publish revised and or new versions of the GNU General Public License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns Each version is given a distinguishing version number If the Program specifies that a certain numbered version of the GNU General Public License or any later version applies to it you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation If the Program does not specify a version number of the GNU General Public License you may choose any version ever published by the Free Software Foundation If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used that proxy s public statement of acceptance of a version permanently authorizes you to choose that version for the Program Later license versions may give you additional or different permissions However no additional obligations are imposed on any author or copyright holder as a
12. 2 1 File commands page 48 The command used for compiling can be specified using the menu entry Settings gt External programs or using the mixvm command sasm Exit File Exits the application Run Debug Runs the currently loaded MIX program up to the next breakpoint It is equivalent to the mixvm s run command see Section 6 2 2 Debug commands page 50 Next Debug Executes the next MIX instruction It is equivalent to the mixvm s next command see Section 6 2 2 Debug commands page 50 Clear breakpoints Debug Clears all currently set breakpoints It is equivalent to the mixvm s cabp command Symbols Debug Opens a dialog showing the list of symbols defined in the currently loaded MIX program The font used to display this list can be customised using the meny entry Settings gt Change font gt Symbol list Toolbar s View Toggles the toolbar s in the gmixvm window s when notebook pages are detached each one has its own toolbar Detached windows Virtual machine View Detached windows Source View Detached windows Devices View These toggles let you detach or re attach the corresponding notebook page Change font Settings Lets you change the font used in the various gmixv widgets i e commad prompt command log Virtual machine Source Devices and Symbol list There is also an entry A11 to change all fonts at once Device output Settings Opens a dialog that lets you specify which
13. 3 3 1 Non interactive mode page 29 for sample usage t User Option time User Option This option must be used in conjuction with r and tells mixvm to print virtual time statistics for the program s execution 48 GNU MIX Development Kit mdk When run without the r flag mixvm enters its interactive mode showing you a prompt like this one MIX gt and waiting for your commands see Section 6 2 Commands page 48 If the optional FILE argument is given the file FILE mix will be loaded into the virtual machine memory before entering the interactive mode The first time mixvm is invoked a directory named mdk is created in your home directory It contains the mixvm configuration file the command history file and by default the block devices files see Section 6 3 Devices page 57 Before showing you the command prompt mixvm looks in the mdk directory for a file named mixguile scm if it exists it is read and evaluated by the embedded Guile interpreter see Section 3 4 3 Defining new functions page 35 You can use the q command line option to skip this file loading q User Option noinit User Option Do not load the Guile initialisation file mdk mixguile scm at startup 6 2 Interactive commands You can enter the interactive mode of the MIX virtual machine by simply invoking mixvm without arguments You will then be greeted by a shell prompt MIX gt which indicates that a new virtual
14. INDEX are zero they can be omitted Finally MOD defaults to 0 5 meaning the whole word 2 1 2 2 Loading operators The following instructions are used to load memory contents into a register LDA Put in rA the contents of cell no M OPCODE 8 MOD fspec rA V LDX Put in rX the contents of cell no M OPCODE 15 MOD fspec rX V LDi Put in rli the contents of cell no M OPCODE 8 i MOD fspec rli lt V LDAN Put in rA the contents of cell no M with opposite sign OPCODE 16 MOD fspec rA V LDXN Put in rX the contents of cell no M with opposite sign OPCODE 23 MOD fspec rX V LDiN Put in rli the contents of cell no M with opposite sign OPCODE 16 i MOD fspec rIi lt V In all the above load instructions the MOD field selects the bytes of the memory cell with address M which are loaded into the requisite register indicated by the OPCODE For instance the word 00 13 01 27 11 represents the instruction LD3 13 1 3 3 Ew A MOD 27 3 8 3 INDEX 1 ADDRESS 00 13 OPCODE 11 Let us suppose that prior to this instruction execution the state of the MIX computer is the following rI1 00 01 rI3 24 12 12 01 02 03 04 05 Chapter 2 MIX and MIXAL tutorial 13 As in this case M 13 rI1 12 we have V M 3 3 01 02 03 04 05 3 3 00 00 00 00 03 note that the s
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16. block size Note that the virtual machine automatically converts between the MIX and ASCII char acter encodings so that you can manipulate char device files with any ASCII editor In addition the reader is not case sensitive i e it automatically converts lowercase letters to their uppercase counterparts since the MIX character set does not include the former The typewriter device no 19 lets you use the standard input and output in your MIXAL programs For instance here is a simple echo program simple echo program TERM EQU 19 the typewriter device BUF EQU 500 input buffer ORIG 1000 START IN BUF TERM read a block 70 chars OUT BUF TERM write the read chars HLT END START Input lines longer than 70 characters 14 words are trimmed On the other hand if you type less than a block of characters whitespace MIX character zero is used as padding Chapter 7 gmixvm the GTK virtual machine 59 7 gmixvm the GTK virtual machine This chapter describes the graphical MIX virtual machine emulator shipped with MDK In addition to having all the command oriented functionalities of the other virtual machines mixvm and mixguile gmixvm offers you a graphical interface displaying the status of the virtual machine the source code of the the downloaded programs and the contents of the MIX devices 7 1 Invoking gmixvm If you have built MDK with GTK support see Chapter 1 Installing MDK page 5 a graphical front end for
17. format shall be used to show the contents of MIX binary block devices The available formats are decimal e g 1234 and MIX word e g 00 00 00 19 18 Devices dir Settings Opens a dialog that lets you choose where the MIX device files will be stored mdk is the default location You can also specify the devices directory using the mixvm command sddir see Section 6 2 4 Configuration commands page 56 Chapter 7 gmixvm the GTK virtual machine 63 External programs Settings This menu command opens a dialog that lets you specify the commands used for editing and compiling MIXAL source files The commands are specified as template strings where the control substring s will be substituted by the actual file name Thus if you want to edit programs using vi running in an xterm you must enter the command template xterm e vi 4s in the corresponding dialog entry These settings can also be changed using the mixvm commands sedit and sasm see Section 6 2 4 Configuration commands page 56 Save Settings Saves the current settings Save on exit Settings Mark this checkbox if you want gmixvm to save its settings every time you quit the program About Help Shows information about gmixvm s version and copyright On the other hand the status bar displays the name of the last loaded MIX file In addition when the mouse pointer is over a MIXAL source file line that contains symbols a list of these symbols
18. mix pmem mix loc 3002 14 09 27 01 13 0237350989 MIX gt You can also load and evaluate a file using the scmf command like this Chapter 3 Getting started 41 MIX scmf path to file file scm Therefore you have at your disposal all the mixguile goodies described above new functions new command definitions hooks inside mixvm and gmixvm In other words these programs are extensible using Scheme See Section 3 4 Using mixguile page 33 for examples of how to do it Chapter 4 Emacs tools 43 4 Emacs tools Everyone writing code knows how important a good editor is Most systems already come with Emacs and excellent programmer s editor MDK adds support to Emacs for both writing and debugging MIX programs A major mode for MIXAL source files eases edition of your code while integration with Emacs debugging interface GUD lets you use mixvm without leaving your favourite text editor This chapter shows how to use the Elisp modules included in MDK assuming that you have followed the installation instructions in See Section 1 4 Emacs support page 6 4 1 MIXAL mode The module mixal mode el provides a new mode mixal mode for editing MIXAL source files When everything is installed correctly Emacs will select it as the major mode for editing files with extension mixal You can also activate mixal mode in any buffer issuing the Emacs command M x mixal mode 4 1 1 Basics The mode for editing mixal source
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20. protecting users freedom to change the software T he systematic 76 GNU MIX Development Kit mdk pattern of such abuse occurs in the area of products for individuals to use which is pre cisely where it is most unacceptable Therefore we have designed this version of the GPL to prohibit the practice for those products If such problems arise substantially in other domains we stand ready to extend this provision to those domains in future versions of the GPL as needed to protect the freedom of users Finally every program is threatened constantly by software patents States should not allow patents to restrict development and use of software on general purpose computers but in those that do we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary To prevent this the GPL assures that patents cannot be used to render the program non free The precise terms and conditions for copying distribution and modification follow TERMS AND CONDITIONS 0 Definitions This License refers to version 3 of the GNU General Public License Copyright also means copyright like laws that apply to other kinds of works such as semiconductor masks The Program refers to any copyrightable work licensed under this License Each licensee is addressed as you Licensees and recipients may be individuals or organizations To modify a work means to copy from or ad
21. registers without an indirection to the memory cells in a real CPU this would mean that they are faster that the previously discussed instructions whose operands are fetched from memory So if you want to store in rA the value 2000 00 00 00 31 16 you can use the binary instruction 31 16 00 03 48 or symbolically Chapter 2 MIX and MIXAL tutorial 15 ENNA 2000 Used in conjuction with the store operations STA STX etc these instructions also allow you to set memory cells contents to concrete values Note that in these address transfer operators the MOD field is not a subfield specificator but serves to define together with OPCODE the concrete operation to be performed 2 1 2 6 Comparison operators So far we have learned how to move values around between the MIX registers and its memory cells and also how to perform arithmetic operations using these values But in order to write non trivial programs other functionalities are needed One of the most common is the ability to compare two values which combined with jumps will allow the execution of conditional statements The following instructions compare the value of a register with V and set the CM indicator to the result of the comparison i e to E G or L equal greater or lesser respectively CMPA Compare rA with V OPCODE 56 MOD fspec CMPX Compare rX with V OPCODE 63 MOD fspec CMPi Compare r
22. result of your choosing to follow a later version Disclaimer of Warranty THERE IS NO WARRANTY FOR THE PROGRAM TO THE EXTENT PER MITTED BY APPLICABLE LAW EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND OR OTHER PARTIES PROVIDE THE PROGRAM AS IS WITHOUT WARRANTY OF ANY KIND EITHER EX PRESSED OR IMPLIED INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU SHOULD THE PROGRAM PROVE DEFEC TIVE YOU ASSUME THE COST OF ALL NECESSARY SERVICING REPAIR OR CORRECTION Limitation of Liability IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER OR ANY OTHER PARTY WHO MODIFIES AND OR CONVEYS THE PROGRAM AS PERMITTED ABOVE BE LIABLE TO YOU FOR DAMAGES INCLUDING ANY GENERAL SPECIAL IN CIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUS TAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAM AGES Interpretation of Sections 15 and 16 If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms reviewing courts shall appl
23. see Section 1 2 Requirements page 5 the configure script with automatically disable this feature with guile yes no User Option without guile User Option Enables disables the Guile support for nixvm and gmixvm and the build of nixguile If the required libraries are missing see Section 1 2 Requirements page 5 the configure script with automatically disable this feature with readline yes no User Option without readline User Option Enables disables the GNU Readline support for mixvm If the required libraries are missing see Section 1 2 Requirements page 5 the configure script with automati cally disable this feature For additional boilerplate configure options see the INSTALL file or run configure help 1 6 Supported platforms GNU MDK has been tested in the following platforms e Debian GNU Linux 2 2 2 3 3 0 3 1 3 2 4 0 5 0 6 0 sid e Redhat GNU Linux 8 0 Ronald Cole 7 0 Agustin Navarro 6 2 Roberto Ferrero e Mandrake 8 0 Agustin Navarro e FreeBSD 4 2 4 3 4 4 4 5 Ying Chieh Liao 5 2 e Solaris 2 8 gcc 2 95 3 Stephen Ramsay e MS Windows 98 SE Cygwin 1 1 8 2 Christoph von Nathusius e Mac OS X 10 1 2 Johan Swanljung Mac OS X 10 4 x 10 5 Darwin Port by Aleix Conchillo Caveats Christoph has only tested mixvm and mixasm on this platform using gcc 2 95 3 2 GLIB 1 2 10 and GNUreadline 4 1 2 He has reported missing history functionalities on a first try If y
24. the currently visible notebook page or the menu entries under View gt Detached windows On the other hand the main window s lower half presents you a mixvm command prompt and a logging area where results of the issued commands are presented These widgets implement a mixvm console which offers almost the same functionality as its CLI counterpart 60 GNU MIX Development Kit mdk When gmixvm is run it creates a directory named mdk in your home directory if it does not already exist The mdk directory contains the program settings the device files used by your MIX programs see Section 6 3 Devices page 57 and a command history file The following sections describe the above mentioned components of gmixvm 7 2 MIXVM console In the lower half of the gmixvm main window you will find a command text entry and above it an echo area These widgets offer you the same functionality as its CLI counterpart mixvm see Chapter 6 mixvm page 47 You can issue almost all mixmv commands at the gmixvm s command prompt in order to manipulate the MIX virtual machine Please refer to See Chapter 6 mixvm page 47 for a description of these commands and to See Chapter 3 Getting started page 27 for a tutorial on using the MIX virtual machine The command prompt offers command line completion for partially typed commands using the TAB key e g if you type lo TAB the command is automatically completed to load If multiple completion
25. this License for any work from that copyright holder and you cure the violation prior to 30 days after your receipt of the notice Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License If your rights have 82 10 11 GNU MIX Development Kit mdk been terminated and not permanently reinstated you do not qualify to receive new licenses for the same material under section 10 Acceptance Not Required for Having Copies You are not required to accept this License in order to receive or run a copy of the Program Ancillary propagation of a covered work occurring solely as a consequence of using peer to peer transmission to receive a copy likewise does not require acceptance However nothing other than this License grants you permission to propagate or modify any covered work These actions infringe copyright if you do not accept this License Therefore by modifying or propagating a covered work you indicate your acceptance of this License to do so Automatic Licensing of Downstream Recipients Each time you convey a covered work the recipient automatically receives a license from the original licensors to run modify and propagate that work subject to this License You are not responsible for enforcing compliance by third parties with this License An entity transaction is a transaction transferring control of an organization or
26. with the command M x mixvm and you will have a mixvm prompt inside a newly created GUD buffer GUD will reflect the current line in the corresponding source file buffer 2 mixvm el has been kindly contributed by Philip E King mixvm el is based on a study of gdb perldb and pdb as found in gud el and rubydb3x el distributed with the source code to the Ruby language Chapter 5 mixasm the MIXAL assembler 45 5 mixasm the MIXAL assembler MIX programs as executed by mixvm are composed of binary instructions loaded into the virtual machine memory as MIX words Although you could write your MIX programs directly as a series of words in binary format you have at your disposal a more friendly assembly language MIXAL see Section 2 2 MIXAL page 19 which is compiled into binary form by mixasm the MIXAL assembler included in MDK In this chapter you will find a complete description of mixasm options 5 1 Invoking mixasm In its simplest form mixasm is invoked with a single argument which is the name of the MIXAL file to be compiled e g mixasm hello will compile either hello or hello mixal producing a binary file named hello mix if no errors are found In addition mixasm can be invoked with the following command line options note that following GNU s conventions we provide a long option name for each available single letter switch mixasm vhul0 o OUTPUT FILE version help usagel ndebug output OUT
27. work material governed by the terms of that license document provided that the further restriction does not survive such relicensing or conveying If you add terms to a covered work in accord with this section you must place in the relevant source files a statement of the additional terms that apply to those files or a notice indicating where to find the applicable terms Additional terms permissive or non permissive may be stated in the form of a sep arately written license or stated as exceptions the above requirements apply either way 8 Termination You may not propagate or modify a covered work except as expressly provided un der this License Any attempt otherwise to propagate or modify it is void and will automatically terminate your rights under this License including any patent licenses granted under the third paragraph of section 11 However if you cease all violation of this License then your license from a particular copyright holder is reinstated a provisionally unless and until the copyright holder explicitly and finally terminates your license and b permanently if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation Moreover your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means this is the first time you have received notice of violation of
28. 00 MIX gt will load hello mix into the virtual machine s memory and set the program counter to the address of the first instruction You can obtain the contents of the program counter using the command pc MIX gt pc Current address 3000 MIX gt After loading it you are ready to run the program using as you surely have guessed the run command MIX gt run Running MIXAL HELLO WORLD done Elapsed time 11 Total program time 11 Total uptime 11 MIX gt Note that now the timing statistics are richer You obtain the elapsed execution time i e the time spent executing instructions since the last breakpoint the total execution time for the program up to now which in our case coincides with the elapsed time since there were no breakpoints and the total uptime for the virtual machine you can load and run more than one program in the same session After running the program the program counter will point to the address after the one containing the HLT instruction In our case asking the value of the program counter after executing the program will give us MIX gt pc Current address 3002 MIX 5 Printing of timing statistics can be disabled using the command timing see Section 6 2 4 Configuration commands page 56 Chapter 3 Getting started 31 You can check the contents of a memory cell giving its address as an argument of the command pmen like this MIX gt pmem 3001 3001 00 00 00 02 05
29. 00 00 00 00 00 0000000000 guile gt You get the idea you have at your disposal all the mixvm and gmixvm commands by means of mix functions But in case you are wondering this is only the beginning You also have at your disposal a whole Scheme interpreter and you can for instance define new functions combining the mix and all other Scheme primitives In the next sections you ll find examples of how to take advantage of the Guile interpreter 3 4 2 Additional MIX Scheme functions The mix function counterparts of the mixvm commands don t return any value and are eval uated only for their side effects possibly including informational messages to the standard output and or error stream When writting your own Scheme functions to manipulate the MIX virtual machine within mixguile see Section 3 4 3 Defining new functions page 35 you ll probably need Scheme functions returning the value of the registers memory cells and so on Don t worry mixguile also offers you such functions For instance to access the numerical value of a register you can use mix reg guile gt mix reg 12 0 guile gt Note that unlike mix preg 12 the expression mix reg 12 in the above example evaluates to a Scheme number and does not produce any side effect guile gt number mix reg I2 St guile gt number mix preg 12 rI2 00 00 0000 ST guile In a similar fashion you can access the memory contents using mix cell
30. 0000000000 0012 00 00 00 00 00 0000000000 MIX gt mix pmem 10 12 0010 00 00 00 00 00 0000000000 0011 00 00 00 00 00 0000000000 0012 00 00 00 00 00 0000000000 MIX gt 68 GNU MIX Development Kit mdk mix sover t f Function The command sover takes as argument either the string T or the string F to set respectively the overflow toggle to true or false Its Scheme counterpart mix sover takes as argument a Scheme boolean value stt true or f For the remaining functions you simply must take into account that when the command arguments are numerical the corresponding Scheme function takes as arguments Scheme number literals On the other hand when the command argument is a string the argument of its associated Scheme function will be a Scheme string By way of example the following invocations are pairwise equivalent MIX gt load samples hello MIX gt mix load samples hello MIX gt next 5 MIX gt mix next 5 8 2 2 Hook functions Hooks are functions evaluated before or after executing a mixvm command or its corre sponding Scheme function wrapper or after an explicit or conditional breakpoint is found during the execution of a MIX program The following functions let you install hooks mix add pre hook command hook Function Adds a function to the list of pre hooks associated with the give command command is a string naming the corresponding mixvm command and hook is a functio
31. 0000000133 MIX gt and convince yourself that address 3001 contains the binary representation of the instruction HLT An address range of the form FROM TO can also be used as the argument of pmen MIX gt pmem 3000 3006 3000 46 58 00 19 37 0786957541 3001 00 00 00 02 05 0000000133 3002 14 09 27 01 13 0237350989 3003 00 08 05 13 13 0002118477 3004 16 00 26 16 19 0268542995 3005 13 04 00 00 00 0219152384 3006 00 00 00 00 00 0000000000 MIX gt In a similar manner you can look at the contents of the MIX registers and flags For instance to ask for the contents of the A register you can type MIX gt preg A rA 00 00 00 00 00 0000000000 MIX gt Use the comand help to obtain a list of all available commands and help COMMAND for help on a specific command e g MIX gt help run run Run loaded or given MIX code file Usage run FILENAME MIX gt For a complete list of commands available at the MIX propmt See Chapter 6 mixvm page 47 In the following subsection you will find a quick tour over commands useful for debugging your programs 3 3 3 Debugging commands The interactive mode of mixvm lets you step by step execution of programs as well as breakpoint setting Use next to step through the program running its instructions one by one To run our two instruction hello mix sample you can do the following MIX gt load hello Program loaded Start address 3000 MIX gt pc C
32. 19 rI4 31 51 2035 rI5 00 00 0000 rI6 00 00 0000 Overflow F Cmp L Note that this is far more flexible that running programs non interactively using mixvm see Section 3 3 1 Non interactive mode page 29 for you can execute any combination of commands you want from a Scheme script not just running and dumping the registers For additional mixguile command line options see Section 8 1 Invoking mixguile page 65 3 5 Using Scheme in mixvm and gmixvm In the previous section see Section 3 4 Using mixguile page 33 we have seen how the Guile shell nixguile offers you the possibility of using Scheme to manipulate a MIx virtual machine and extend the set of commands offered by mixvm and gmixvm This possibility is not limited to the mixguile shell Actually both mixvm and gmixvm incorporate an embedded Guile interpreter and can evaluate Scheme expressions To evaluate a single line expression at the mixvm or gmixvm command prompt simply write it and press return the command parser will recognise it as a Scheme expression because it is parenthesized and will pass it to the Guile interpreter A sample mixvm session using Scheme expressions could be MIX gt load hello Program loaded Start address 3000 MIX gt define a mix loc MIX gt run Running MIXAL HELLO WORLD done Elapsed time 11 Total program time 11 Total uptime 11 MIX gt mix pmem a 3000 46 58 00 19 37 0786957541 MIX gt
33. GNU MDK GNU MIX Development Kit Edition 1 2 8 for GNU MDK Version 1 2 8 January 2014 by Jose Antonio Ortega Ruiz jao gnu org This manual is for GNU MDK version 1 2 8 January 2014 a set of utilities for devel oping programs using Donald Knuth s MIX mythical computer and MIXAL its assembly language Copyright c 2000 2001 2002 2003 2004 2005 2006 2008 2009 2010 2013 2014 Free Software Foundation Inc Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with the Invariant Sections being GNU General Public License with the Front Cover Texts being A GNU Manual and with the Back Cover Texts as in a below A copy of the license is included in the section entitled GNU Free Documentation License a The FSF s Back Cover Text is You have the freedom to copy and modify this GNU manual Buying copies from the FSF supports it in developing GNU and promoting software freedom Short Contents eiert TEE 1 Acknowledgements auod ade ep oed rad os EE RR dea 3 RN GEAR EE EE 5 2 MIX and MIXAL tutorial 23 sia ean eee ia 9 d Getting started iscia cet wedge Due da E Vo e did d 2 A EE 43 5 mixasm the MIXAL assembler 2 aa 5 er ARENS 45 6 mixvm the MIX computer simulator Lun 4T 7 gmixvm the GTK virtual machine 59 8 mixguile the Sc
34. IX computer simulator 49 load file mix file command This command loads a binary file file mix into the virtual machine memory and positions the program counter at the beginning of the loaded program This address is indicated in the MIXAL source file as the operand of the END pseudoinstruction Thus if your sample mixal source file contains the line END 3000 and you compile it with mixasm to produce the binary file sample mix you will load it into the virtual machine as follows MIX gt load sample Program loaded Start address 3000 MIX gt run file mix file command edit When executed without argument this command initiates or resumes execution of instructions from the current program counter address Therefore issuing this com mand after a successful load will run the loaded program until either a HLT instruc tion or a breakpoint is found If you provide a MIX filename as argument the given file will be loaded as with load file and executed If run is invoked again after program execution completion i e after the HLT instruction has been found in a previous run the program counter is repositioned and execution starts again from the beginning as a matter of fact a load command preserving the currently set breakpoints is issued before resuming execution file mixal file command The source file file mixal is edited using the editor defined in the environment variable MDK_EDITOR If this variable
35. O to 3999 i e two bytes are enough to address a memory cell and the following registers rA A register General purpose register holding a word Usually its contents serves as the operand of arithmetic and storing instructions rX X register General purpose register holding a word Often it acts as an exten sion or a replacement of rA rJ J jump register This register stores positive two byte values usually repre senting a jump address 10 GNU MIX Development Kit mdk rli rI2 rI3 r14 rI5 rI6 Index registers These six registers can store a signed two byte value Their contents are used as indexing values for the computation of effective memory addresses In addition the MIX computer contains An overflow toggle a single bit with values on or off In this manual this toggle is denoted ov A comparison indicator having three values EQUAL GREATER or LESS In this manual this indicator is denoted CM and its possible values are abbreviated as E G and L Input output block devices Each device is labelled as un where n runs from 0 to 20 In Knuth s definition u0 through u7 are magnetic tape units u8 through 15 are disks and drums u16 is a card reader u17 is a card writer u18 is a line printer and u19 is a typewriter terminal and u20 a paper tape Our implementation maps these devices to disk files except for u19 which represents the standard output As noted above the MIX computer c
36. PUT FILE list LIST FILE file The meaning of these options is as follows V User Option version User Option Prints version and copyleft information and exits h User Option help User Option u User Option usage User Option Prints a summary of available options and exits 0 User Option ndebug User Option Do not include debugging information in the compiled file saving space but disallow ing breakpoint setting at source level and symbol table inspection under mixvm o output file User Option output output file User Option By default the given source file file mixal is compiled into file mix You can provide a different name for the output file using this option User Option list list_file User Option This option causes mixasm to produce in addion to the mix file an ASCII file containing a summary of the compilation results The file is named after the MIXAL source file changing its extension to m1s if no argument is provided otherwise the listing file is named according to the argument Chapter 6 mixvm the MIX computer simulator 4T 6 mixvm the MIX computer simulator This chapter describes mixvm the MIX computer simulator mixvm is a command line inter face programme which simulates the MIX computer see Section 2 1 The MIX computer page 9 It is able to run MIXAL programs see Section 2 2 MIXAL page 19 previously compiled with the MIX assembler see Chapter 5
37. The source code for a work means the preferred form of the work for making modi fications to it Object code means any non source form of a work Appendix A Copying 77 A Standard Interface means an interface that either is an official standard defined by a recognized standards body or in the case of interfaces specified for a particular programming language one that is widely used among developers working in that language The System Libraries of an executable work include anything other than the work as a whole that a is included in the normal form of packaging a Major Component but which is not part of that Major Component and b serves only to enable use of the work with that Major Component or to implement a Standard Interface for which an implementation is available to the public in source code form A Major Component in this context means a major essential component kernel window system and so on of the specific operating system if any on which the executable work runs or a compiler used to produce the work or an object code interpreter used to run it The Corresponding Source for a work in object code form means all the source code needed to generate install and for an executable work run the object code and to modify the work including scripts to control those activities However it does not include the work s System Libraries or general purpose tools or generally available free
38. UM How to use this License for your documents To use this License in a document you have written include a copy of the License in the document and put the following copyright and license notices just after the title page Copyright C year your name Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with no Invariant Sections no Front Cover Texts and no Back Cover Texts A copy of the license is included in the section entitled GNU Free Documentation License If you have Invariant Sections Front Cover Texts and Back Cover Texts replace the with Texts line with this with the Invariant Sections being list their titles with the Front Cover Texts being list and with the Back Cover Texts being list If you have Invariant Sections without Cover Texts or some other combination of the three merge those two alternatives to suit the situation If your document contains nontrivial examples of program code we recommend releasing these examples in parallel under your choice of free software license such as the GNU General Public License to permit their use in free software Concept Index Concept Index nba P T 28 mall ciales 27 amls EE 45 A ie EE 9 address transfer operators sssssss 14 arithmetic operators essere 13 assembler 22 e
39. X block devices ssssssssssseesss Ie on gnixvm the GTK virtual machine 59 7 1 Invoking gmixvm ele as 59 1 2 MIXVM console dE EE ERE WISEN RENE 60 7 3 MIX virtual machine 60 7 4 MIXAL source view 61 Zb MIX devices View Lie exse meer REENEN ee cer E res 61 7 6 Menu and status bar 61 mixguile the Scheme virtual machine 65 8 1 Invoking mixguile tte Ru ek eere ed 65 8 2 Scheme functions reference esee 66 8 2 1 mixvm command wrapperg eee 66 8 2 2 Hook function 68 8 2 3 Additional VM functions eee 69 9 Reporting Bugs 73 Appendix A Copimng nuana as nan 75 A 1 GNU General Public License e T9 A 2 GNU Free Documentation License 0 0 eee eee eee 86 Concept Index 41 4 deu te gege betont eR nae s 93 Instructions and commands 95 Introduction 1 Introduction In his book series The Art of Computer Programming published by Addison Wesley D Knuth uses an imaginary computer the MIX and its associated machine code and assembly languages to ilustrate the concepts and algorithms as they are presented The MIX s architecture is a simplified version of those found in real CISC CPUs and the MIX assembly language MIXAL provides a set of primitives that will be very familiar to any person with a minimum experience in assembly programming The MIX MIXAL definition is powerful and complete enough to provide a virtual development platform for wr
40. X instruction 0 0 eee eee eee eee eee 9 MIX regiBUGr nie ek eR ERE RED iieri yia 9 MIX word 8 sisas EN rhe ere nee Re LEE n 9 MIX Ad se rere t Kries eg er 9 19 27 45 MM e er adder Gee dete tae 28 45 AAA ti knnt bon EErEE 33 65 mizg il EE 65 MIKU ii is 28 PETRY EE 47 N TEE 31 non interactive ooooooocrrrrrrrrro mo 39 non interactive mode 28 29 O EE 22 Oasis a io 10 Overflow toggle so 2 rra dede 10 94 EE 30 EE 30 post hook 22 sie i449 E e Re ha PE AE 36 A E E E E E E 36 EE 31 problems 2 EES RE T3 E EE 32 Q e UO EE 13 EE 9 TORIO EE 9 O EE 33 Inscr done ua Der NERA eet igi ed 9 Td EE 9 n PP aii a 30 D a apo abe oe 9 S O seated teers euegienies 32 SPPA EE 32 GNU MIX Development Kit mdk Scheme function 35 Scheme script 39 SCM EE 40 O Seed eege 17 shift operatorg esses 17 Source fil ed cance naka encia RESE T Ed perds 21 storing operators isses o 13 SUSSEStIONS mena a bee erige had 13 T tail recursion ciocia cece eee eens 93 Dk CN 18 teuer ee EE EI Zeie 2T V virtual machine 28 W W expresslOnS eet A ed EE ere toes abe 22 A a E A 9 Instructions and commands 95 Instructions and commands A I ADO Edi PEPPER EN ET Rue Dus 63 Niro gu pden ups qui e AE E 16 ripper 13 INCA te Eege Ree ETT Ius PF eI eia 14 IH rr 20 INGI EE 14 INGX 5 2226 hee eesprerird s Ped EE bp s iG 14 C TOG EE a E 16 EE 51
41. ansparent copies include plain ASCII without markup Texinfo input format LaTEX input format SGML or XML using a publicly available DTD and standard conforming simple HTML PostScript or PDF designed for human modification Examples of transparent image formats include PNG XCF and JPG Opaque formats include proprietary formats that can be read and edited only by proprietary word processors SGML or XML for which the DTD and or processing tools are not generally available and the machine generated HTML PostScript or PDF produced by some word processors for output purposes only The Title Page means for a printed book the title page itself plus such following pages as are needed to hold legibly the material this License requires to appear in the title page For works in formats which do not have any title page as such Title Page means the text near the most prominent appearance of the work s title preceding the beginning of the body of the text A section Entitled XYZ means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language Here XYZ stands for a specific section name mentioned below such as Acknowledgements Dedications Endorsements or History To Preserve the Title of such a section when you modify the Document means that it remains a section Entitled XYZ according to this definition
42. apt all or part of the work in a fashion requiring copyright permission other than the making of an exact copy The resulting work is called a modified version of the earlier work or a work based on the earlier work A covered work means either the unmodified Program or a work based on the Pro gram To propagate a work means to do anything with it that without permission would make you directly or secondarily liable for infringement under applicable copyright law except executing it on a computer or modifying a private copy Propagation includes copying distribution with or without modification making available to the public and in some countries other activities as well To convey a work means any kind of propagation that enables other parties to make or receive copies Mere interaction with a user through a computer network with no transfer of a copy is not conveying An interactive user interface displays Appropriate Legal Notices to the extent that it includes a convenient and prominently visible feature that 1 displays an appropriate copyright notice and 2 tells the user that there is no warranty for the work except to the extent that warranties are provided that licensees may convey the work under this License and how to view a copy of this License If the interface presents a list of user commands or options such as a menu a prominent item in the list meets this criterion 1 Source Code
43. ases of MDK The development branch is available as a Git repository located at e git git savannah gnu org mdk git After you have downloaded the source tarball unpack it in a directory of your choice using the command tar xfvz mdk X Y tar gz where X Y stands for the downloaded version the current stable release being version 1 2 8 1 2 Requirements In order to build and install MDK you will need the following libraries installed in your system GLIB 2 16 0 required GNU Flex 2 5 required GTK 2 16 0 optional Libglade 2 6 0 optional GNU Readline optional GNU Libguile 2 0 optional If present readline and history are used to provide command completion and history management to the command line MIX virtual machine mixvm GTK and libglade are needed if you want to build the graphical interface to the MIX virtual machine gmixvm Finally if libguile is found the MDK utilities will be compiled with Guile support and will be extensible using Scheme Please note you need both the libraries and the headers this means both the library package and the dev package if you do not compile your libraries yourself ex installing libgtk2 0 0 and libgtk2 0 0 dev on Debian 1 See MDK s Git page for more information on using the unstable source tree Note however that the rest of this manual is about the stable release 6 GNU MIX Development Kit mdk 1 3 Basic installation MDK us
44. atter of fact you can directly set breakpoints at source code lines using the command sbp LINE NO e g MIX gt sbp 4 Breakpoint set at line 7 MIX gt sbp sets the breakpoint at the first meaningful source code line thus in the above example we have requested a breakpoint at a line which does not correspond to a MIX instruction and the breakpoint is set at the first line containing a real instruction after the given one To unset breakpoints use cbpa ADDRESS and cbp LINE NO or cabp to remove all currently set breakpoints You can also set conditional breakpoints i e tell mixvm to interrupt program execution whenever a register a memory cell the comparison flag or the overflow toggle change using the commands sbp rmco see Section 6 2 2 Debug commands page 50 Chapter 3 Getting started 33 MIXAL lets you define symbolic constants either using the EQU pseudoinstruction or starting an instruction line with a label which assigns to the label the value of the current memory address Each MIXAL program has therefore an associated symbol table which you can inspect using the psym command For our hello world sample you will obtain the following output MIX gt psym START 3000 TERM 19 MSG 3002 MIX gt Other useful commands for debugging are strace which turns on tracing of executed intructions pbt which prints a backtrace of executed instructions and weval which eval uates w expressions on the fly For a complet
45. cs which will teach you the basics of the MIX architecture and how to program a MIX computer using MIXAL 2 1 The MIX computer In this section you will find a description of the MIX computer its components and in struction set 2 1 1 MIX architecture The basic information storage unit in the MIX computer is the byte which stores positive values in the range 0 63 Note that a MIX byte can be then represented as 6 bits instead of the common 8 bits for a regular byte Unless otherwise stated we shall use the word byte to refer to a MIX 6 bit byte A MIX word is defined as a set of 5 bytes plus a sign The bytes within a word are numbered from 1 to 5 being byte number one the most significant one The sign is denoted by index 0 Graphically Sample MIX words are 12 00 11 01 63 and 12 11 34 43 00 You can refer to subfields within a word using a field specification or fspec of the form L R where L denotes the first byte and R the last byte of the subfield When L is zero the subfield includes the word s sign An fspec can also be represented as a single value F given by F 8 L R thus the fspec 1 3 denoting the first three bytes of a word is represented by the integer 11 The MIX computer stores information in registers that can store either a word or two bytes and sign see below and memory cells each one containing a word Specifically the MIX computer has 4000 memory cells with addresses
46. ctions or setting breakpoints Enter interactive mode 3 The device files are stored by default in a directory called mdk which is created in your home directory the first time mixvm is run You can change this default directory using the command devdir when running mixvm in interactive mode see Section 6 2 4 Configuration commands page 56 The mixguile program allows you to execute arbitrary combinations of mixvm commands using Scheme non interactively See Section 3 4 5 Scheme scripts page 39 30 GNU MIX Development Kit mdk 3 3 2 Interactive mode To enter the MIX virtual machine interactive mode simply type mixvm RET at your shell command prompt This command enters the mixvm command shell You will be presented the following command prompt MIX gt The virtual machine is initialised and ready to accept your commands The mixvm command shell uses GNU s readline so that you have at your disposal command completion using TAB and history functionality as well as other line editing shortcuts common to all utilities using this library for a complete description of readline s line editing usage see Section Command Line Editing in Readline Usually the first thing you will want to do is loading a compiled MIX program into memory This is acomplished by the load command which takes as an argument the name of the mix file to be loaded Thus typing MIX gt load hello RET Program loaded Start address 30
47. cution time will be a function of the input size and the answer to our question is commonly given as the asymptotic behaviour as a function of the input size At any rate to compute this asymptotic behaviour we need a measure of how long execution of a single instruction takes in our virtual CPU Therefore each MIX instruction will have an associated execution time given in arbitrary units in a real computer the value of this unit will depend on the hardware configuration When our MIX virtual machine executes programs it will optionally give you the value of their execution time based upon the execution time of each single instruction In the following table the execution times in the above mentioned arbitrary units of the MIX instructions are given NOP 1 ADD 2 SUB 2 MUL 10 DIV 12 NUM 10 CHAR 10 HLT 10 SLx 2 SRx 2 LDx 2 STx 2 JBUS 1 IOC 1 IN 1 QUT 1 JRED 1 Jx 1 INCx 1 DECx 1 ENTx 1 ENNx 1 CMPx 1 MOVE 1 2F Chapter 2 MIX and MIXAL tutorial 19 In the above table F stands for the number of blocks to be moved given by the FSPEC subfield of the instruction SLx and SRx are a short cut for the byte shifting operations LDx denote all the loading operations STx are the storing operations Jx stands for all the jump operations and so on with the rest of abbreviations 2 2 MIXAL In the previous sections we have listed all the available MIX binary instructions As we have shown each instruction is represented by a word w
48. d either when the specified number of instructions have been fetched or a breakpoint is found whatever happens first If run without arguments one instruc tion is executed If next is invoked again after program execution completion i e after the HLT instruction has been found in a previous run the program counter is repositioned and execution starts again from the beginning as a matter of fact a load command preserving the currently set breakpoints is issued before resuming execution sbp line number debug command cbp line no debug command Sets a breakpoint at the specified source file line number If the line specified corre sponds to a command or to a MIXAL pseudoinstruction which does not produce a MIX instruction in the binary file such as ORIG or EQU the breakpoint is set at the first source code line giving rise to a MIX instruction after the specified one Thus for our sample hello mixal file 1 hello mixal say hello world in MIXAL 2 3 label ins operand comment 4 TERM EQU 19 the MIX console device number 5 ORIG 1000 start address 6 START OUT MSG TERM output data at address MSG 7 trying to set a breakpoint at line 5 will produce the following result MIX gt sbp 5 Breakpoint set at line 7 MIX gt since line 7 is the first one compiled into a MIX instruction at address 3000 The command cbp clears a previously set breakpoint at the given source file line spba address debu
49. d for at least three years and valid for as long as you offer spare parts or customer support for that product model to give anyone who possesses the object code either 1 a copy of the Corresponding Source for all the software in the product that is covered by this License on a durable physical medium customarily used for software interchange for a price no more than your reasonable cost of physically performing this con veying of source or 2 access to copy the Corresponding Source from a network server at no charge c Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source This alternative is allowed only occasionally and noncommercially and only if you received the object code with such an offer in accord with subsection 6b d Convey the object code by offering access from a designated place gratis or for a charge and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge You need not require recipients to copy the Corresponding Source along with the object code If the place to copy the object code is a network server the Corresponding Source may be on a different server operated by you or a third party that supports equivalent copying facilities provided you maintain clear directions next to the object code saying where to find the Corresponding Source Regardless of what server hosts the Corresponding Source you
50. d for you 3 4 5 Scheme scripts Another useful way of using mixguile is writing executable scripts that perform a set of commands for you This is done using the mixguile switch s being a Guile shell mixguile accepts all the command options of guile type mixguile h for a list of all available command options For instance if you have a very useful MIX program foo mix which you want to run often you don t have to fire a MIX virtual machine load and run it every time you can write a Scheme script instead usr bin mixguile s E runprimes execute the primes mix program load the file you want to run mix load samples primes execute it mix run print the contents of registers mix pall 3 D You may have noticed that break hooks can be implemented in terms of command hooks associated to mix run and mix next As a matter of fact they are implemented this way take a look at the file install dir share mdk mix vm stat scm if you are curious 40 GNU MIX Development Kit mdk Just save the above script to a file named say runtest make it executable chmod x runtest and well execute it from the Unix shell runtest Program loaded Start address 3000 Running done Elapsed time 190908 Total program time 190908 Total uptime 190908 rA 30 30 30 30 30 0511305630 rX 30 30 32 32 39 0511313959 rJ 47 18 3026 rli 00 00 0000 rI2 55 51 3571 rI3 00 19 00
51. d in a register with room to only 5 bytes plus sign When this occurs the operation result modulo 1 073 741 823 the maximum value storable in a MIX word is stored in rA and the overflow toggle is set to TRUE 2 1 2 5 Address transfer operators In these instructions M the address of the instruction after indexing is used as a number instead of as the address of a memory cell Consequently M can have any valid word value De it s not limited to the 0 3999 range of a memory address ENTA Enter M in rA OPCODE 48 MOD 2 rA lt M ENTX Enter M in rX OPCODE 55 MOD 2 rx lt M ENTi Enter M in rli OPCODE 48 i MOD 2 r1i lt M ENNA Enter M in rA OPCODE 48 MOD 3 rA lt M ENNX Enter M in rX OPCODE 55 MOD 3 rX lt M ENNi Enter M in rli OPCODE 48 i MOD 3 rli lt M INCA Increase rA by M OPCODE 48 MOD 0 rA lt rA M INCX Increase rX by M OPCODE 55 MOD 0 rX lt rX M INCi Increase rli by MW OPCODE 48 i MOD 0 rIi lt rli M DECA Decrease rA by M OPCODE 48 MOD 1 rA lt rA M DECX Decrease rX by M OPCODE 55 MOD 1 rX lt rX M DECi Decrease rli by M OPCODE 48 i MaOD 0 rli lt rIi M In the above instructions the subfield ADDRESS acts as an immediate indexed operand and allow us to set directly the contents of the MIX
52. d in the mdk directory and the output is also written to files at the same location Note that device tabs will appear as they are used by the MIX program being run and that loading a new MIX program will close all previously open devices The input output for binary block devices tapes and disks is a list of MIX words which can be displayed either in decimal or word format e g 67 or 00 00 00 01 03 The format used by gmixvm can be configured using the Settings gt Device output menu command for each binary device You can change the font used to display the devices content using the Settings gt Change font gt Devices menu command 7 6 Menu and status bars The menu bar gives you access to the following commands Load File Opens a file dialog that lets you specify a binary MIX file to be loaded in the virtual machine s memory It is equivalent to the mixvm s load command see Section 6 2 1 File commands page 48 Edit File Opens a file dialog that lets your specify a MIXAL source file to be edited It is equivalent to the mixvm s edit command see Section 6 2 1 File commands page 48 The program used for editing can be specified using the menu entry Settings gt External programs or using the mixvm command sedit 62 GNU MIX Development Kit mdk Compile File Opens a file dialog that lets your specify a MIXAL source file to be compiled It is equivalent to the mixvm s compile command see Section 6
53. d preserve in the section all the substance and tone of each of the contributor acknowledgements and or dedications given therein Preserve all the Invariant Sections of the Document unaltered in their text and in their titles Section numbers or the equivalent are not considered part of the section titles Delete any section Entitled Endorsements Such a section may not be included in the Modified Version Do not retitle any existing section to be Entitled Endorsements or to conflict in title with any Invariant Section Preserve any Warranty Disclaimers If the Modified Version includes new front matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document you may at your option designate some or all of these sections as invariant To do this add their titles to the list of Invariant Sections in the Modified Version s license notice These titles must be distinct from any other section titles 90 GNU MIX Development Kit mdk You may add a section Entitled Endorsements provided it contains nothing but endorsements of your Modified Version by various parties for example statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard You may add a passage of up to five words as a Front Cover Text and a passage of up to 25 words as a Back Cover Text to the end of the list of Cover Texts in the Modified
54. dad 22 2 2 4 W expressloliS 2 2d pers EROR ad E EE 22 2 2 5 Localsymbols seht esee eere La ER Rs 23 2 2 6 Literal constants ecnerccs tiesin ti Prun rn a E aa 24 3 Getting started naana nannaa ee eee 27 3 1 Writing asourcebnle nneur annerer 27 3 2 Compiling ENN EELER EE EA E 28 3 3 Running the program 28 3 3 1 Non interactive mode 29 3 3 2 Interactive mode 30 GNU MIX Development Kit mdk 3 3 3 Debugging commande 31 3 4 Using mixguile ii iss seit eere Re COE Ve rh Ras 33 3 4 1 The mixguile shell o ooooooocoommmrcmrromc 33 3 4 2 Additional MIX Scheme function 34 3 4 8 Defining new Duncttonsg eese 35 3 4 4 Hook function 36 3 4 4 1 Command books 36 3 4 4 2 Break books 39 3 4 5 Scheme scripta m nnn 39 3 5 Using Scheme in mixvm and gmixvm 0 eee eee eee 40 Emacs A Rape OE ERE TD ROCA 43 41 MIXAL mode eere br ER br reete DR EEN I aree Res 43 AL Tid BASICS EE 43 44 2 Help systems le bach Re eb eR ERR EN 43 4 1 3 Compiling and running cnc 44 42 GUD int gration sebo NEE Ae d 44 mixasm the MIXAL assembler 45 5 1 Invoking mix sm ee ses e EEN REENEN ENEE Edd 45 mixvm the MIX computer simulator AT 6 1 Invoking mizwm en 4T 6 2 Interactive commande 48 6 2 1 File commands crre coss ERENNERT EE E 48 6 2 2 Debug commande 50 6 2 3 State commande 54 6 2 4 Configuration commande 56 6 2 5 Scheme commande 57 6 3 MI
55. device used e g disk4 dev and written its output there The virtual machine can also report the execution time of the program according to the virtual time spent in each of the binary instructions see Section 2 1 2 12 Execution times page 18 Printing of execution time statistics is activated with the t flag running mixvm t r hello RET produces the following output MIXAL HELLO WORLD Execution time 11 Sometimes you will prefer to store the results of your program in MIX registers rather than writing them to a device In such cases mixvm s d flag is your friend it makes mixvm to dump the contents of its registers and flags after executing the loaded program For instance typing the following command at your shell s prompt mixvm d r hello you will obtain the following output MIXAL HELLO WORLD rA 00 00 00 00 00 0000000000 rX 00 00 00 00 00 0000000000 rJ 00 00 0000 rli 00 00 0000 rI2 00 00 0000 rI3 00 00 0000 rI4 00 00 0000 rI5 00 00 0000 rI6 00 00 0000 Overflow F Cmp E which in addition to the program s outputs and execution time gives you the contents of the MIX registers and the values of the overflow toggle and comparison flag admittedly rather uninteresting in our sample As you can see running programs non interactively has many limitations You can not peek the virtual machine s memory contents not to mention stepping through your program s instru
56. dge See Sot de 28 45 assemblys cde ige vpp rre is 19 B binary operatori z ienveesaecede ees ea he eee 22 binary programs ielemmt tert e e bn 28 break hooked osse AEN ERE RE 39 Let Te EE 32 D gsisoesi mbr RI IR EERU EDI THU PE weds 73 lj 9 cl ia es 9 EE 10 eege el MP 22 comparison indicator 0c eee eee eee 10 comparison Ooperatorg 0 ee eee eee 15 coinpIling i comicas ra e EELER SE 28 conversion OpeETatOTS eene 17 E exection Hme eene 18 F FDL GNU Free Documentation License 86 field specification oooooocoooorcrcrcnnroco 9 SE EE 9 G global hook mosca E 38 EMI deet a ere ER Ee 59 GPL GNU General Public License 75 TEA hen eebe Ee 59 else ep 59 93 hook function ve EEN NENNEN EEN 36 I IndexessiiekemkRertzebke tte L 9 input output dewvices 0 cece eee ee eee 10 input output operators 0 eee eee ee eee 16 IESEL a wands 9 instruction EE eme Sere choca eme Serge 11 interactive mode 28 30 IntroductlOn a u epe cre aia 1 enee ge 15 L literal constants 0 cece eee eee ee eee 24 RRE 30 loading operators eese 12 local sacmbols o 23 M MEMO AE SE Mir 9 memory Cells ioco serere pride 9 miscellaneous operators eee ee ee eee 18 Mi anita circa a e E pEi 9 MIX architecture 0ooooocccccoorcccccnncccoo 9 MIX assembly language susnrrrurnrrrun 19 MIX Bytes soit gees bereet ia 9 MIX computer 9 MI
57. dit MIXAL source files with the edit com mand TEMPLATE must contain the control characters 4s to mark the place where the source s file name will be inserted For instance if you type MIX gt sedit emacsclient s MIX gt issuing the mixvm command edit foo mixal will invoke the operating system com mand emacsclient foo mixal pedit prints the current value of the edit command template sasm TEMPLATE config command pasm config command sasm sets the command to be used to compile MIXAL source files with the compile command template must contain the control characters s to mark the place where the source s file name will be inserted For instance if you type MIX gt sasm mixasm 1 s MIX gt issuing the mixvm command compile foo mixal will invoke the operating system command mixasm 1 foo mixal pasm prints the current value of the compile command template sddir DIRNAME config command pddir config command MIX devices see Section 6 3 Devices page 57 are implemented as regular files stored by default inside mdk The sddir command lets you specify an alternative location for storing these device files while pddir prints the current device directory Chapter 6 mixvm the MIX computer simulator 57 Finally you can change the default command prompt MIX gt using the prompt com mand prompt PROMPT config command Changes the command prompt to prompt If you want to include white space s at the end o
58. duce them compiling MIXAL source files using the MIXAL assembler mixasm On the other hand mixguile offers you the possibility of manipulating a MIX virtual machine through a set of Scheme functions so that you can use this programming language to interact with the virtual machine In addition mixvm and gmixvm are also able to interpret Scheme scripts using an embedded Guile interpreter that is you can use Scheme as an extension language to add new functionalities to these programs This manual gives you a tutorial of MIX and MIXAL and a thorough description of the use of the MDK utilities Acknowledgements 3 Acknowledgements Many people have further contributed to MDK by reporting problems suggesting various improvements or submitting actual code Here is a list of these people Help me keep it complete and exempt of errors Philip Ellis King provided MIXAL test programs pinpointing bugs in the first MDK release and useful discussions as well Philip has also contributed with the Emacs port of mixvm and influenced the gmixvm GUI design with insightful comments and prototypes Aleix Conchillo has been following MDK s development for many years indefatigably chasing and fixing bugs and suggesting many improvements He s also the original author of the Fink and Macports ports Pieter E J Pareit is the author of the Emacs MIXAL mode and has also contributed many bug fixes Michael Scholz is the author of the German translation
59. e applies to any manual or other work in any medium that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License Such a notice grants a world wide royalty free license unlimited in duration to use that work under the conditions stated herein The Document below refers to any such manual or work Any member of the public is a licensee and is addressed as you You accept the license if you copy modify or distribute the work in a way requiring permission under copyright law A Modified Version of the Document means any work containing the Document or a portion of it either copied verbatim or with modifications and or translated into another language A Secondary Section is a named appendix or a front matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document s overall subject or to related matters and contains nothing that could fall directly within that overall subject Thus if the Document is in part a textbook of mathematics a Secondary Section may not explain any mathematics The relationship could be a matter of historical connection with the subject or with related matters or of legal commercial philosophical ethical or political position regarding them The Invariant Sections are certain Secondary Sections whose titles are designated as being those of Invariant Sections in th
60. e description of all available MIX commands See Chapter 6 mixvm page 47 3 4 Using mixguile With mixguile you can run a MIX simulator embedded in a Guile shell that is using Scheme functions and programs As with mixvm mixguile can be run both in interactive and non interactive modes The following subsections provide a quick tour on using this MIX emulator 3 4 1 The mixguile shell If you simply type mixguile RET at the command prompt you ll be presented a Guile shell prompt like this guile At this point you have entered a Scheme read eval print loop REPL which offers you all the Guile functionality plus a new set of built in procedures to execute and debug MIX programs Each of the mixvm commands described in the previous sections and in see Chapter 6 mixvm page 47 have a Scheme function counterpart named after it by prepending the prefix mix to its name Thus to load our hello world program you can simply enter guile mix load hello Program loaded Start address 3000 guile and run it using mix run guile gt mix run Running MIXAL HELLO WORLD done Elapsed time 11 Total program time 11 Total uptime 11 guile In the same way you can execute it step by step using the Scheme function mix next or set a breakpoint 34 GNU MIX Development Kit mdk guile mix sbp 4 Breakpoint set at line 5 guile or if you one to peek at a register contents guile gt mix preg Ai rA
61. e instructions check the overflow toggle to decide whether to jump or not JOV Jump if OV is set and turn it off OPCODE 39 MOD 2 JNOV Jump if OV is not set and turn it off OPCODE 39 MOD 3 In the following instructions the jump is conditioned to the contents of the comparison flag 16 JL JE JG JGE JNE JLE GNU MIX Development Kit mdk Jump if CM L OPCODE 39 MOD 4 Jump if CM E OPCODE 39 MOD 5 Jump if CM G OPCODE 39 MOD 6 Jump if CM does not equal L OPCODE 39 MOD 7 Jump if CM does not equal E OPCODE 39 MOD 8 Jump if CM does not equal G OPCODE 39 MOD 9 You can also jump conditioned to the value stored in the MIX registers using the following instructions JAN JAZ JAP JANN JANZ JANP JXN JXZ JXP JXNN JXNZ JXNP JiN JiZ JiP JiNN JiNZ JiNP Jump if the content of rA is respectively negative zero positive non negative non zero or non positive OPCODE 40 MOD 0 1 2 3 4 5 Jump if the content of rX is respectively negative zero positive non negative non zero or non positive OPCODE 47 MOD 0 1 2 3 4 5 Jump if the content of rli is respectively negative zero positive non negative non zero or non positive OPCODE 40 i MOD 0 1 2 3 4 5 2 1 2 8 Input output operators As explained in previous sections see Section 2 1 1 MIX architecture page 9 the MIX computer can interact with a series
62. e notice that says that the Document is released Appendix A Copying 87 under this License If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant The Document may contain zero Invariant Sections If the Document does not identify any Invariant Sections then there are none The Cover Texts are certain short passages of text that are listed as Front Cover Texts or Back Cover Texts in the notice that says that the Document is released under this License A Front Cover Text may be at most 5 words and a Back Cover Text may be at most 25 words A Transparent copy of the Document means a machine readable copy represented in format whose specification is available to the general public that is suitable for revising the document straightforwardly with generic text editors or for images com posed of pixels generic paint programs or for drawings some widely available drawing editor and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters copy made in an otherwise Transparent file format whose markup or absence of markup has been arranged to thwart or discourage subsequent modification by readers is not Transparent An image format is not Transparent if used for any substantial amount of text A copy that is not Transparent is called Opaque Examples of suitable formats for Tr
63. e run Thus if you have installed both the next hooks described earlier and the global hook above executing mix next will yield the following result guile gt mix next 5 next invoked with arguments 5 slog invoked with arguments off MIXAL HELLO WORLD Stopped at line 7 MSG ALF MIXAL slog invoked with arguments on guile gt Chapter 3 Getting started 39 Adventurous readers may see the above global hook as the beginning of a command log utility or a macro recorder that saves your commands for replay 3 4 4 2 Break hooks We have seen in the previous section how to associate hooks to command execution but they are not the whole story You can also associate hook functions to program interruption that is specify functions that should be called every time the execution of a MIX program is stopped due to the presence of a breakpoint either explicit or conditional Break hooks take as arguments the line number and memory address at which the break occurred A simple hook that logs the line and address of the breakpoint could be defined as define break hook lambda line address display Breakpoint encountered at line display line display and address display address newline and installed for explicit and conditional breakpoints using mix add break hook break hook mix add cond break hook break hook after that every time the virtual machine encounters a breakpoint break code shall be evaluate
64. ed by MOD of the memory cell with address M For instance suppose that we have the following contents of MIX registers and memory cells rI2 00 63 31 10 11 00 11 22 where n denotes the contents of the nth memory cell and rI2 the contents of register rI27 Let us consider the binary instruction I 00 32 02 11 10 For this instruction we have ADDRESS 00 32 32 INDEX 02 2 MOD 11 1 3 OPCODE 10 1 The actual memory address the instruction refers to is obtained by adding to ADDRESS the value of the rT register denoted by INDEX 2 In general X will denote the contents of entity X thus by definition V M MOD 12 GNU MIX Development Kit mdk M V Note that when computing V using a word and an fspec we apply a left padding to the bytes selected by MOD to obtain a complete word as the result ADDRESS rI2 32 63 31 M MOD 10 11 00 11 22 1 3 00 00 10 11 00 H In the following subsections we will assign to each MIX instruction a mnemonic or symbolic name For instance the mnemonic of OPCODE 10 is LD2 Thus we can rewrite the above instruction as LD2 32 2 1 3 or for a generic instruction MNEMONIC ADDRESS INDEX MOD Some instructions are identified by both the OPCODE and the MOD fields In these cases the MOD will not appear in the above symbolic representation Also when ADDRESS or
65. ember 2002 Copyright c 2000 2001 2002 Free Software Foundation Inc 51 Franklin St Fifth Floor Boston MA 02110 1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed 0 PREAMBLE The purpose of this License is to make a manual textbook or other functional and useful document free in the sense of freedom to assure everyone the effective freedom to copy and redistribute it with or without modifying it either commercially or non commercially Secondarily this License preserves for the author and publisher a way to get credit for their work while not being considered responsible for modifications made by others This License is a kind of copyleft which means that derivative works of the document must themselves be free in the same sense It complements the GNU General Public License which is a copyleft license designed for free software We have designed this License in order to use it for manuals for free software because free software needs free documentation a free program should come with manuals providing the same freedoms that the software does But this License is not limited to software manuals it can be used for any textual work regardless of subject matter or whether it is published as a printed book We recommend this License principally for works whose purpose is instruction or reference 1 APPLICABILITY AND DEFINITIONS This Licens
66. ements of this License to extend the patent license to downstream recipients Knowingly relying means you have actual knowledge that but for the patent license your conveying the covered work in a country or your recipients use of the covered work in a country would infringe one or more identifiable patents in that country that you have reason to believe are valid If pursuant to or in connection with a single transaction or arrangement you convey or propagate by procuring conveyance of a covered work and grant a patent license to some of the parties receiving the covered work authorizing them to use propagate modify or convey a specific copy of the covered work then the patent license you grant is automatically extended to all recipients of the covered work and works based on it A patent license is discriminatory if it does not include within the scope of its cover age prohibits the exercise of or is conditioned on the non exercise of one or more of the rights that are specifically granted under this License You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software under which you make payment to the third party based on the extent of your activity of conveying the work and under which the third party grants to any of the parties who would receive the covered work from you a discriminatory patent license a in connection with copies of the c
67. eparately received it d If the work has interactive user interfaces each must display Appropriate Legal Notices however if the Program has interactive interfaces that do not display Appropriate Legal Notices your work need not make them do so A compilation of a covered work with other separate and independent works which are not by their nature extensions of the covered work and which are not combined with it such as to form a larger program in or on a volume of a storage or distribution medium is called an aggregate if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation s users beyond what the individual works permit Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate Appendix A Copying 79 6 Conveying Non Source Forms You may convey a covered work in object code form under the terms of sections 4 and 5 provided that you also convey the machine readable Corresponding Source under the terms of this License in one of these ways a Convey the object code in or embodied in a physical product including a phys ical distribution medium accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange b Convey the object code in or embodied in a physical product including a physi cal distribution medium accompanied by a written offer vali
68. erful programming language Scheme to extend the MDK virtual machine emulators see Section 3 5 Using Scheme in mixvm and gmixvm page 40 for samples of how to do it The following subsections describe available functions the MIX Scheme library 8 2 1 mixvm command wrappers For each of the mixvm commands listed in Section 6 2 Commands page 48 there is a corresponding Scheme function named by prefixing the command name with mix e g mix load mix run and so on These command wrappers are implemented using a generic command dispatching function mixvm cmd command argument Function Dispatchs the given command to the MIX virtual appending the provided argument Both command and argument must be strings The net result is as writing command argument at the mixvm or gmixvm command prompt For instance you can invoke the run command at the mixvm prompt in three equivalent ways MIX gt run hello MIX gt mix run hello MIX gt mixvm cmd run hello only the two last forms can be used at the mixguile prompt or inside a Scheme script The mix functions evaluate to a unspecified value If you want to check the result of the last mixvm command invocation use the mix last result function Chapter 8 mixguile the Scheme virtual machine 67 mix last result Function Returns Zt if the last mixvm command invocation was successful f otherwise Using this function we could improve the script for running a program prese
69. ermit When the Document is included in an aggregate this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document If the Cover Text requirement of section 3 is applicable to these copies of the Document then if the Document is less than one half of the entire aggregate the Document s Cover Texts may be placed on covers that bracket the Document within the aggregate or the electronic equivalent of covers if the Document is in electronic form Otherwise they must appear on printed covers that bracket the whole aggregate TRANSLATION Iranslation is considered a kind of modification so you may distribute translations of the Document under the terms of section 4 Replacing Invariant Sections with translations requires special permission from their copyright holders but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections You may include a translation of this License and all the license notices in the Document and any Warranty Disclaimers provided that you also include the original English version of this License and the original versions of those notices and disclaimers In case of a disagreement between the translation and the original version of this License or a notice or disclaimer the original version will prevail If a section in the Document is Entitled Acknowledgements Dedications or His
70. es GNU Autoconf and Automake tools and therefore should be built and installed without hassle using the following commands inside the source directory configure make make install where the last one must be run as root The first command configure will setup the makefiles for your system In particular configure will look for GTK and libglade and if they are present will generate the appropiate makefiles for building the gmixvm graphical user interface Upon completion you should see a message with the configuration results like the following GNU MDK 1 2 8 has been successfully configured Type make to build the following utilities mixasm MIX assembler mixvm MIX virtual machine with readline support with guile support gmixvm mixvm GTK GUI with guile support mixguile the mixvm guile shell where the last lines may be missing if you lack the above mentioned libraries The next command make will actually build the MDK programs in the following loca tions mixutils mixasm mixutils mixvm mixgtk gmixvm mixguile mixguile You can run these programs from within their directories but I recommend you to install them in proper locations using make install from a root shell 1 4 Emacs support MDK includes extensive support for Emacs Upon installation all the elisp code is in stalled in PREFIX share mdk where PREFIX stands for your installation root directory e g usr
71. es the given function using the provided command line arguments For instance you can write the following Scheme script usr bin mixguile e main s Hit execute a given program and print the registers define main lambda args load the file provided as a command line argument mix load cadr args 66 GNU MIX Development Kit mdk execute it mix run print the contents of registers mix pall save it in a file called say foo make it executable and run it as foo hello This invocation will cause the evaluation of the main function with a list of command line parameters as its argument foo hello in the above example Note that command line options to mixguile must be written in their own line after the symbol q User Option Do not load user s initialisation file When mixguile starts up it looks for a file named mixguile scm in the user s MDK configuration directory mdk and loads it if it exists This option tells mixguile to skip this initialisation file loading 8 2 Scheme functions reference As we have previously pointed out mixguile embeds a MIX virtual machine that can be accessed through a set of Scheme functions that is of a Scheme library Conversely mixvm and gmixvm contain a Guile interpreter and are able to use this same Scheme library as well as all the other Guile Scheme primitives and any user defined function Therefore you have at your disposal a pow
72. etween the ADDRESS INDEX and MOD fields if they are present White space is used to separate the label operation code and operand parts of the instruction We have already listed the mnemonics associated will each MIX instructions sample MIXAL instructions representing MIX instructions are HERE LDA 2000 HERE represents the current location counter LDX HERE 2 1 3 this is a comment JMP 1234 2 2 2 MIXAL directives MIXAL instructions can be either one of the MIX machine instructions see Section 2 1 2 MIX instruction set page 11 or one of the following assembly pseudoinstructions ORIG Sets the value of the memory address to which following instructions will be allocated after compilation EQU Used to define a symbol s value e g SYM EQU 2 200 3 CON The value of the given expression is copied directly into the current memory address ALF Takes as operand five characters constituting the five bytes of a word which is copied directly into the current memory address END Marks the end of the program Its operand gives the start address for program execution The operand of ORIG EQU CON and END can be any expression evaluating to a constant MIX word i e either a simple MIXAL expression composed of numbers symbols and bi nary operators see Section 2 2 3 Expressions page 22 or a w expression see Section 2 2 4 W expressions page 22 All MIXAL programs must contain an END directive with a twofold end first it
73. ext 5 MIX LOADED Program successfully loaded 6 MIX EMPTY No program loaded mix vm error Function mix vm break Function mix vm cond break Function mix vm halted Function mix vm running Function mix vm loaded Function mix vm empty Function Predicates asking whether the current virtual machine status is MIX ERROR MIX BREAK etc 70 GNU MIX Development Kit mdk mix reg register Function mix set reg register value Function mix reg evaluates to a number which is the contents of the specified register mix set reg sets the contents of the given register to value The register can be specified either as a string A X etc or as a symbol A X etc For instance guile gt mix reg A 2341 guile gt mix set reg A 2000 ok guile gt define reg a mix reg A guile gt display reg a 2000 guile gt mix cell cell_no Function mix set cell cell_no value Function Evaluate and set the contents of the memory cell number cell no Both cell no and value are Scheme numbers mix loc Function Evaluates to the value of the location counter i e the address of the next instruction to be executed mix over Function mix set over t f Function mix over evaluates to t if the overflow toggle is set and to f otherwise The value of the overflow toggle can be modified using mix set over mix cmp Function mix set cmp L E G Function Evaluate and set the comparison flag Po
74. f prior to the instruction execution we have 1200 20 21 22 23 24 rA 01 02 03 04 05 we will end up with 1200 20 04 05 23 24 rA 01 02 03 04 05 As a second example ST2 1000 0 will set the sign of 10007 to that of rI2 2 1 2 4 Arithmetic operators The following instructions perform arithmetic operations between rA and rX register and memory contents ADD Add and set OV if overflow OPCODE 1 MOD fspec rA lt rA V 14 GNU MIX Development Kit mdk SUB Sub and set OV if overflow OPCODE 2 MOD fspec rA lt rA V MUL Multiply V times rA and store the 10 bytes product in rAX OPCODE 3 MOD fspec rAX lt rA x V DIV rAX is considered a 10 bytes number and it is divided by V OPCODE 4 MOD fspec rA lt rAX V rX lt reminder In all the above instructions rA is one of the operands of the binary arithmetic operation the other being V that is the specified subfield of the memory cell with address M padded with zero bytes on its left side to complete a word In multiplication and division the register X comes into play as a right extension of the register A so that we are able to handle 10 byte numbers whose more significant bytes are those of rA the sign of this 10 byte number is that of rA rX s sign is ignored Addition and substraction of MIX words can give rise to overflows since the result is store
75. f the new prompt bracket prompt using double quotes e g prompt gt gt 6 2 5 Scheme commands If you have compiled MDK with 1ibguile support see Section 1 5 Special configure flags page 7 mixvm will start and initialise an embedded Guile Scheme interpret when it is invoked That means that you have at your disposal at mixvm s command prompt all the Scheme primitives described in Section 3 4 Using mixguile page 33 and Chapter 8 mixguile page 65 as well as any other function or hook that you have defined in the initialisation file mdk mixguile scm To evaluate a Scheme function simply type it at the mixvm command prompt see Section 3 5 Using Scheme in mixvm and gmixvm page 40 for a sample Compared to the mixguile program this has only one limitation the expressions used in mixvm cannot span more than one line You can get over this inconvenience writing your multiline Scheme expressions in a file and loading it using the scmf command scmf FILE NAME scheme command Loads the given Scheme file and evaluates it using the embedded Guile interpreter 6 3 MIX block devices The MIX computer comes equipped with a set of block devices for input output operations see Section 2 1 2 8 Input output operators page 16 mixvm implements these block de vices as disk files with the exception of block device no 19 typewriter terminal which is redirected to standard input output When you request an output operation on a
76. files is inherited from fundamental mode meaning that all your favorite editing operations will still work If you want a short introduction to Emacs type C h t inside Emacs to start the tutorial Mixal mode adds font locking If you do not have font locking globally enabled you can turn it on for mixal mode by placing the following line in your emacs file add hook mixal mode hook turn on font lock You can also customize the colors used to colour your mixal code by changing the requisite faces This is the list of faces used by mixal mode e font lock comment face Face to use for comments e mixal font lock label face Face to use for label names e mixal font lock operation code face Face to use for operation code names e mixal font lock assembly pseudoinstruction face Face to use for assembly pseudo instruction names 4 1 2 Help system When coding your program you will be thinking looking up documentation and editing files Emacs already helps you with editing files but Emacs can do much more In particular looking up documentation is one of its strong points Besides the info system which you are probably already using mixal mode defines commands for getting particular information about a MIX operation code With M x mixal describe operation code or its keyboard shortcut C h o you will get the documentation about a particular MIX operation code Keep in mind that these are not assembly MIXAL pseudoinstructions When the
77. for instance telling it where the program starts and ends or to reposition the location counter see below MIX instructions and assembler directives are written in MIXAL one per source file line according to the following pattern LABEL MNEMONIC OPERAND COMMENT where OPERAND is of the form ADDRESS INDEX M0D Items between square brackets are optional and LABEL is an alphanumeric identifier a symbol which gets the current value of the location counter and can be used in subsequent expressions MNEMONIC isa literal denoting the operation code of the instruction e g LDA STA see see Section 2 1 2 MIX instruction set page 11 or an assembly pseudoinstruction e g ORG EQU ADDRESS is an expression evaluating to the address subfield of the instruction We shall call them collectively MIXAL instructions 20 GNU MIX Development Kit mdk INDEX is an expression evaluating to the index subfield of the instruction which de faults to 0 i e no use of indexing and can only be used when ADDRESS is present MOD is an expression evaluating to the mod subfield of the instruction Its default value when omitted depends on OPCODE COMMENT any number of spaces after the operand mark the beggining of a comment i e any text separated by white space from the operand is ignored by the assembler note that spaces are not allowed within the OPERAND field Note that spaces are not allowed b
78. g change debug command Clears all currently set breakpoints symbol name debug command MIXAL programs can define symbolic constants using either the EQU pseudoinstruc tion or a label at the beginning of a line Thus in the program fragment VAR EQU 2168 ORIG 4000 START LDA VAR the symbol VAR stands for the value 2168 while START is assigned the value 4000 The symbol table can be consulted from the mixvm command line using psym followed by the name of the symbol whose contents you are interested in When run without arguments psym will print all defined symbols and their values The virtual machine can also show you the instructions it is executing using the following commands strace on off debug command strace on enables instruction tracing When tracing is enabled each time the virtual machine executes an instruction due to your issuing a run or next command it is 52 GNU MIX Development Kit mdk printed in its canonical form that is with all expressions evaluated to their numerical values and if the program was compiled with debug information as it was originally typed in the MIXAL source file Instruction tracing is disabled with strace off command A typical tracing session could be like this MIX gt strace on MIX gt next 3000 OUT 3002 0 2 3 START OUT MSG TERM MIXAL HELLO WORLD Elapsed time 1 Total program time 1 Total uptime 1 MIX gt next 3001 HLT 0 0 HLT End of prog
79. g command cbpa address debug command Sets a breakpoint at the given memory address The argument must be a valid MIX memory address i e it must belong into the range 0 3999 Note that no check is performed to verify that the specified address is reachable during program execution Chapter 6 mixvm the MIX computer simulator 51 sbpr cbpr sbpm cbpm sbpo cbpo sbpc cbpc cabp psym No debug information is needed to set a breakpoint by address with sbpa The command cbpa clears a previously set breakpoint at the given memory address AIXIJI Ti debug command AIXIJITi debug command Sets a conditional breakpoint on the specified register change For instance sbpr I1 will cause an interruption during program execution whenever the contents or register I1 changes A previously set breakpoint is cleared using the cbpr command address debug command address debug command Sets a conditional breakpoint on the specified memory cell change The argument must be a valid MIX memory address i e it must belong into the range 0 3999 For instance sbpm 1000 will cause an interruption during program execution whenever the contents or of the memory cell number 1000 changes A previously set breakpoint is cleared using the cbpm command debug command debug command Sets clears a conditional breakpoint on overflow toggle change debug command debug command Sets clears a conditional breakpoint on comparison fla
80. he following command at your shell prompt mixasm hello RET If the source file contains no errors this will produce a binary file called hello mix which can be loaded and run by the MIX virtual machine Unless the mixasm option 0 is provided the assembler will include debug information in the executable file for a complete description of all the compilation options see Chapter 5 mixasm page 45 Now your are ready to run your first MIX program as described in the following section 3 3 Running the program MIX is a mythical computer so it is no use ordering it from your favorite hardware provider MDK provides three software simulators of the computer though They are e mixvm a command line oriented simulator e gmixvm a GTK based graphical interface to mixvm and e mixguile a Guile shell with a built in MIX simulator All three simulators accept the same set of user commands but offer a different user interface as noted above In this section we shall describe some of these commands and show you how to use them from mixvm s command line You can use them as well at gmixvm s command prompt see Chapter 7 gmixvm page 59 or using the built in Scheme primitives of mixguile see Section 3 4 Using mixguile page 33 Using the MIX simulators you can run your MIXAL programs after compiling them with mixasm into binary mix files mixvm can be used either in interactive or non interactive mode In the second case mixvm wi
81. heme virtual machine 65 9 Reporting EE 73 A COPE iria A redeas v SUR A E 75 Concept deL AT 93 Instructions and commande 95 Table of Contents Introduction ardido sede na d A OR 1 Acknowledgements sss 3 1 Installing MDE 4 aexutioA Reb ka e RATER RUE RO ulta 9 1 1 Download the source tarball eee eee 5 1 2 Requirements sss i cue Rel rod td aia Inia ade 5 1 3 Basic installation 0 00 c ccc eee eee ees 6 1 4 macs support EE 6 1 5 Special configure ag 7 1 6 Supported platforms 0 cece eee eee eee d 2 MIX and MIXAL tutorial 9 2 1 The MIX computer 9 2 1 1 MIX archtecture re 9 2 1 2 MIX instruction get 11 2 1 2 1 Instruction structure 11 2 1 2 2 Loading operators esses eee 12 2 1 2 8 Storing operatorg sees 13 2 1 2 4 Arithmetic operators 0c cece eee 13 2 1 2 5 Address transfer operatorg 0 00 e eee ee eee 14 2 1 2 6 Comparison operators 00 eens 15 2 1 2 7 Jump operators 0 eee eee eens 15 2 1 2 8 Input output operators 0 eee eee ee 16 2 1 2 9 Conversion operatorg 0 0 c cece eee eee eens 17 2 1 2 10 Shift operators 0 e eee eee eee ee 17 2 1 2 11 Miscellaneous operators ssseeeeeeeeeeeee 18 2 1 2 12 Execution mes 18 EE 19 2 2 1 Basic program structure 19 2 2 2 MIXAL directives ne 20 2 2 9 JEXpEreB8IOn 2 2 e kie a ety Ee Rd ER deg
82. hich is fetched from memory and executed by the MIX virtual CPU As is the case with real computers the MIX knows how to decode instructions in binary format the so called machine language but a hu man programmer would have a tough time if she were to write her programs in machine language Fortunately the MIX computer can be programmed using an assembly language MIXAL which provides a symbolic way of writing the binary instructions understood by the imaginary MIX computer If you have used assembler languages before you will find MIXAL a very familiar language MIXAL source files are translated to machine language by a MIX assembler which produces a binary file the actual MIX program which can be directly loaded into the MIX memory and subsequently executed In this section we describe MIXAL the MIX assembly language The implementation of the MIX assembler program and MIX computer simulator provided by MDK are described later on see Chapter 3 Getting started page 27 2 2 1 Basic program structure The MIX assembler reads MIXAL files line by line producing when required a binary instruction which is associated to a predefined memory address To keep track of the current address the assembler maintains an internal location counter which is incremented each time an instruction is compiled In addition to MIX instructions you can include in MIXAL file assembly directives or pseudoinstructions addressed at the assembler itself
83. ho rization keys or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made If you convey an object code work under this section in or with or specifically for use in a User Product and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term regardless of how the transaction is characterized the Corresponding Source conveyed under this section must be accompanied by the Installation Information But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product for example the work has been installed in ROM The requirement to provide Installation Information does not include a requirement to continue to provide support service warranty or updates for a work that has been modified or installed by the recipient or for the User Product in which it has been modified or installed Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the ne
84. ich sets a breakpoint at a specified line number before executing it guile gt define my load and run with bp lambda file line mix load file mix sbp line mix run guile gt my load and run with bp samples primes 10 Program loaded Start address 3000 Breakpoint set at line 10 Running Stopped breakpoint at line 10 address 3001 Elapsed time 1 Total program time 1 Total uptime 45 guile As a third example the following function loads a program runs it and prints the contents of the memory between the program s start and end addresses guile gt define my run lambda file 36 GNU MIX Development Kit mdk mix load file let start mix loc mix run mix pmem start mix loc guile my run hello Program loaded Start address 3000 Running MIXAL HELLO WORLD done Elapsed time 11 Total program time 11 Total uptime 11 3000 46 58 00 19 37 0786957541 3001 00 00 00 02 05 0000000133 3002 14 09 27 01 13 0237350989 guile gt As you can see the possibilities are virtually unlimited Of course you don t need to type a function definition each time you start mixguile You can write it in a file and load it using Scheme s load function For instance you can create a file named say functions scm with your definitions or any Scheme expression and load it at the mixguile prompt guile gt load functions scm Alternatively you can make mixguile to load it for y
85. ight as follows e Start with an accumulated result w equal to 0 e Take the first expression of the comma separated list and evaluate it For instance if the w expression is 1 2 2 4 2000 S2 we evaluate first S1 2 let s suppose that 1 equals 265230 then S1 2 265232 00 01 00 48 16 e Evaluate the expression within parenthesis reducing it to an f spec of the form L R In our previous example the expression between parenthesis already has the desired form 2 4 e Substitute the bytes of the accumulated result w designated by the f spec using those of the previous expression value In our sample w 00 00 00 00 00 and we must substitute bytes 2 3 and 4 of wi using values from 265232 We need 3 bytes and we take the least significant ones 00 48 and 16 and insert them in positions 2 3 and 4 of w obtaining w 00 00 48 16 00 e Repeat this operation with the remaining terms acting on the new value of w In our example if say S2 1 1 we must substitute the first byte of wi using one byte the least significant from 2000 that is 16 since 2000 00 00 00 31 16 and therefore we obtain w 16 00 48 16 00 summing up we have obtained 265232 1 4 2000 1 1 16 00 48 16 00 268633088 As a second example in the w expression 1 1 2 66 4 5 we first take two bytes from 1 00 and 01 and store them as bytes 1 and 2 of the resul
86. is not set the following ones are tried out in order X_EDITOR EDITOR and VISUAL If invoked without argument the source file for the currently loaded MIX file is edited The command used to edit source files can also be configured using the sedit command see Section 6 2 4 Configuration commands page 56 compile file mixal file command The source file file mixal is compiled with debug information enabled using mixasm If invoked without argument the source file for the currently loaded MIX fie is recompiled The compilation command can be set using the sasm command see Section 6 2 4 Configuration commands page 56 pprog file command psrc file command Print the path of the currently loaded MIX program and its source file MIX gt load samples primes Program loaded Start address 3000 MIX gt pprog samples primes mix MIX gt psrc home jao projects mdk gnu samples primes mixal MIx gt 50 GNU MIX Development Kit mdk Finally you can use the quit command to exit mixvm quit file command Exit mixvm saving the current configuration parameters in mdk mixvm config 6 2 2 Debug commands Sequential execution of loaded programs can be interrupted using the following debug com mands next ins number debug command This command causes the virtual machine to fetch and execute up to ins number instructions beginning from the current program counter position Execution is in terrupte
87. isplay and address display address newline mix add break hook break hook Break hook functions are entirely implemented in Scheme using regular post hooks for the next and run commands If you are curious you can check the Scheme source code at prefix share mdk mixguile vm stat scm where prefix stands for your root install directory usualy usr or usr local See Section 3 4 4 Hook functions page 36 for further examples on using hook functions 8 2 3 Additional VM functions When writing non trivial Scheme extensions using the MIX Scheme library you will prob ably need to evaluate the contents of the virtual machine components registers memory cells and so on For instance you may need to store the contents of the A register in a variable The Scheme functions described so far are of no help you can print the contents of A using mix preg A but you cannot define a variable containing the contents of A To address this kind of problems the MIX Scheme library provides the following additional functions mixvm status Function mix vm status Function Return the current status of the virtual machine as a number mixvm status or as a symbol mix vm status Posible return values are mixvm status mix vm status 0 MIX ERROR Loading or execution error 1 MIX BREAK Breakpoint encountered 2 MIX COND BREAK Conditional breakpoint 3 MIX HALTED Execution terminated 4 MIX RUNNING Execution stopped after n
88. iting quite complex programs and close enough to real computers to be worth using when learning programming techniques At any rate if you want to learn or improve your programming skills a MIX development environment would come in handy The MDK package aims at providing such virtual development environment on a GNU box Thus MDK offers you a set of utilities to simulate the MIX computer and to write compile run and debug MIXAL programs As of version 1 2 8 MDK includes the following programs mixasm MIXAL assembler Assembler which translates MIXAL source files into pro grams that can be run and debugged by mixvm mixguile or gmixvm mixvm MIX virtual machine Emulation of the MIX computer with a CLI gmixvm A GTK GUI for the MIX virtual machine Provides all of mixvm functionality accessible through a graphical interface mixguile A Guile shell with an embedded MIX virtual machine and built in commands to manipulate it using Scheme mixal mode el An Emacs major mode for MIXAL source files editing providing syntax high lighting documentation lookup and invocation of mixvm within Emacs mixvm el This elisp program allows running mixvm inside an Emacs GUD buffer provid ing concurrent edition and debugging of MIXAL programs mixvm and gmixvm implement a simulator of the MIX computer giving you a virtual machine for executing and debugging MIX programs These binary programs could be written by hand but it is easier to pro
89. ium provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice keep intact all notices stating that this License and any non permissive terms added in accord with section 7 apply to the code keep intact all notices of the absence of any warranty and give all recipients a copy of this License along with the Program You may charge any price or no price for each copy that you convey and you may offer support or warranty protection for a fee Conveying Modified Source Versions You may convey a work based on the Program or the modifications to produce it from the Program in the form of source code under the terms of section 4 provided that you also meet all of these conditions a The work must carry prominent notices stating that you modified it and giving a relevant date b The work must carry prominent notices stating that it is released under this Li cense and any conditions added under section 7 This requirement modifies the requirement in section 4 to keep intact all notices c You must license the entire work as a whole under this License to anyone who comes into possession of a copy This License will therefore apply along with any applicable section 7 additional terms to the whole of the work and all its parts regardless of how they are packaged This License gives no permission to license the work in any other way but it does not invalidate such permission if you have s
90. j 50 J CDpa issnesenesterta icd ia daa 50 DEE 16 EE erer ere Deis 51 DEE 16 el 51 DEE 16 ele EE 51 JAN Zaid ieu Use Agen ten bise 16 CDDE irener Pec uber t rabeen ques beet ie briques 51 VAP m 16 Change OM turco t E deed 62 JARZ ssnkese ka ia RERE DOR Y ERA 16 CHA EEN Fe D IEN TT Clear breaknoints eee e eee eee ee 62 leed ege ps 16 CMPA pe CI 15 Jii penes esa s dere EE 16 E RER 15 IGE iia ira d ne bata ERA NIRE RES 16 GMPX circio dnb ad Pura a draca bala susie RH Eara 15 DK BCEE 16 COMPA US perpren in toh nare sceueoe Grays GENEA 49 GERS 16 Compile ses 62 DE BEE 16 A ne sabi bok bawe be ERES 20 JINA 0 oras 16 O ETa iota 16 Np M 16 D Jluilbeseribegseeehezeerseegerao e uiuis 16 DECA ooo ccc cece b eee ccbeeeeeceeee 14 VE ere e ee 16 DECH 14 JMP S eec eem os 15 101216 Ee ae e AE 14 INE cata esae 16 Detached windows Lor 62 JNOV idee ie Bau AE rene ae dere E PPP VES 15 Device output 0 0 cee e eene 62 Br M M 15 Devices di cece ccc ee eee cc ceeees 62 JRED EE 16 EE 14 KEE 15 JANE e rrr 16 JANN auis sprint rri mais a hei d dress Ds 16 E JAN Davis ira sl manii an Poe a dai dd 16 A e b a bete Pa prac pete pes 49 JN 16 Jo EN NR TERRIER PEREAT PERROS 61 A A uud blade eee ARS ieee 16 rip METTE 20 JKZ sse 16 ENNA Nee egene ee don idos RRE RNE pi Aa 14 l ER 14 L ENNX AA dbz ed e eR DEDERE E 14 E EREECHEN 14 jJ 12
91. li with V OPCODE 56 i MOD fspec As explained above these instructions modify the value of the MIX comparison indicator but maybe you are asking yourself how do you use this value enter jump operators in the next subsection 2 1 2 7 Jump operators The MIX computer has an internal register called the location counter which stores the address of the next instruction to be fetched and executed by the virtual CPU You cannot directly modify the contents of this internal register with a load instruction after fetching the current instruction from memory it is automatically increased in one unit by the MIX However there is a set of instructions which we call jump instructions which can alter the contents of the location counter provided some condition is met When this occurs the value of the next instruction address that would have been fetched in the absence of the jump is stored in rJ except for JSJ and the location counter is set to the value of M so that the next instruction is fetched from this new address Later on you can return to the point when the jump occurred reading the address stored in rJ The MIX computer provides the following jump instructions With these instructions you force a jump to the specified address Use JSJ if you do not care about the return address JMP Unconditional jump OPCODE 39 MOD 0 JSJ Unconditional jump but rJ is not modified OPCODE 39 MOD 1 Thes
92. ll load your program into memory execute it producing any output due to MIXAL OUT instructions present in the program and exit when it encounters a HLT instruction In interactive mode you will enter a shell prompt which allows you issuing commands to the running virtual machine This commands will permit you to load run and debug programs as well as to inspect the MIX computer state register contents memory cells contents and so on 2 In Knuth s definition the operand always starts at a fixed column number and the use of quotation is therefore unnecessary As mixasm releases this requirement marking the beginning and end of the ALF operand disambiguates the parser s recognition of this operand when it includes blanks Note that double quotes are not part of the MIX character set and therefore no escape characters are needed within ALF s operands Chapter 3 Getting started 29 3 3 1 Non interactive mode To make mixvm work in non interactive mode use the r flag Thus to run our hello mix program simply type mixvm r hello RET at your command prompt and you will get the following output MIXAL HELLO WORLD Since our hello world program uses MIX s device number 19 as its output device see Section 3 1 Writing a source file page 27 the output is redirected to the shell s standard output Had you used any other MIX output devices disks drums line printer etc mixvm would have created a file named after the
93. local You can copy the elisp files to a directory that is in your load path or you can add the above directory to it Assuming that the installing prefix is usr local you can do it by adding to your emacs file the following line setq load path cons usr local share mdk load path MIXAL programs can be written using Emacs and the elisp program share mdk mixal mode el contributed by Pieter E J Pareit It provides font locking interactive help compiling assistance and invocation of the MIX virtual machine via a new major mode called mixal mode To start mixal mode automatically whenever you edit a MIXAL source file add the following lines to your emacs file autoload mixal mode mixal mode t Chapter 1 Installing MDK T add to list auto mode alist mixal mixal mode In addition mixvm can be run within an Emacs GUD buffer using the elisp program share mdk mixvm el contributed by Philip E King mixvm el provides an interface be tween MDK s mixvm and Emacs via GUD Place this file in your load path optionally adding the following line to your emacs file autoload mixvm mixvm mixvm gud interaction t 1 5 Special configure flags You can fine tune the configuration process using the following switches with configure enable gui yes no User Option disable gui User Option Enables disables the build of the MIX virtual machine GUI gmixvm If the required libraries are missing
94. machine has been initialised and is ready to execute your commands As we have already mentioned this command prompt offers you command line editing facilities which are described in the Readline user s manual chances are that you are already familiar with these command line editing capabilities as they are present in many GNU utilities e g the bash shell In a nutshell readline provides command completion using the TAB key and command history using the cursor keys A history file containing the last commands typed in previous sessions is stored in the MDK configuration directory mdk As a beginner your best friend will be the help command which shows you a summary of all available MIX commands and their usage its syntax is as follows help command nixvm command Prints a short description of the given command and its usage If command is omitted help prints the short description for all available commands 6 2 1 File commands You have at your disposal a series of commands that let you load and execute MIX exe cutable files as well as manipulate MIXAL source files 1 The default command prompt MIX gt can be changed using the prompt command see Section 6 2 4 Configuration commands page 56 2 The readline functionality will be available if you have compiled MDK with readline support i e if GNU readline is installed in your system This is ofte the case in GNU Linux and BSD systems Chapter 6 mixvm the M
95. marks the end of the assembler job and in the second place its mandatory operand indicates the start address for the compiled program that is the address at which the virtual MIX machine must begin fetching instructions after loading the program It is also very common although not mandatory to include at least an ORIG directive to mark the initial value of the assembler s location counter remember that it stores the address associated with each compiled MIX instruction Thus a minimal MIXAL program would be 5 In fact Knuth s definition of MIXAL restricts the column number at which each of these instruction parts must start The MIXAL assembler included in MDK mixasm does not impose such restriction Chapter 2 MIX and MIXAL tutorial 21 ORIG 2000 set the initial compilation adress NOP this instruction will be loaded at adress 2000 HLT and this one at address 2001 END 2000 end of program start at address 2000 this line is not parsed by the assembler The assembler will generate two binary instructions NOP 00 00 00 00 00 and HLT 00 00 02 05 which will be loaded at addresses 2000 and 2001 Execution of the program will begin at address 2000 Every MIXAL program should also include a HLT instruction which will mark the end of program execution but not of program compilation The EQU directive allows the definition of symbolic names for specific values For instance we could rewrite the above program as follows
96. mbly language MIXAL as described in Knuth s TAOCP is assumed for a compact reminder see Chapter 2 MIX and MIXAL tutorial page 9 3 1 Writing a source file MIXAL programs can be written as ASCII files with your editor of choice Here you have the mandatory hello world as written in the MIXAL assembly language 1 hello mixal say hello world in MIXAL 2 3 label ins operand comment 4 TERM EQU 19 the MIX console device number 5 ORIG 1000 start address 6 START OUT MSG TERM output data at address MSG 7 HLT halt execution 8 MSG ALF MIXAL 9 ALF HELL 10 ALF 0 WOR 11 ALF Mp 4 12 END START end of the program 13 MIXAL source files should have the extension mixal when used with the MDK utilities As you can see in the above sample each line in a MIXAL file can be divided into four fields separated by an arbitrary amount of whitespace characters blanks and or tabs While in Knuth s definition of MIXAL each field must start at a fixed pre defined column number the MDK assembler loosens this requirement and lets you format the file as you see fit The only restrictions retained are for comment lines like 1 4 which must begin with an asterisk placed at column 1 and for the label field see below which if present must also start at column 1 The four fields in each non comment line are an optional label which either refers to the current memory address as START and MSG in lines 7 a
97. mixasm page 45 The simulator allows inspection of the MIX computer components registers memory cells comparison flag and overflow toggle step by step execution of MIX programmes and breakpoint setting to aid you in debugging your code For a tutorial description of mixvm usage See Section 3 3 Running the program page 28 6 1 Invoking mixvm mixvm can be invoked with the following command line options note that following GNU s conventions we provide a long option name for each available single letter switch mixvm vhurdtq version help usagel run dump time noinit FILE mixll The meaning of these options is as follows V User Option version User Option Prints version and copyleft information and exits h User Option help User Option u User Option usage User Option Prints a summary of available options and exits r User Option run User Option Loads the specified FILE and executes it After the program execution mixvm exits FILE must be the name of a binary mix program compiled with mixasm If your program does not produce any output use the d flag see below to peek at the virtual machine s state after execution d User Option dump User Option This option must be used in conjuction with r and tells mixvm to print the value of the virtual machine s registers comparison flag and overflow toggle after executing the program named FILE See See Section
98. n which takes a single argument a string list of the commands arguments The following scheme code defines a simple hook and associates it with the run command define run hook lambda args display argument list display args newline mix add pre hook run run hook Pre hooks are executed in the order they are added before invoking the corresponding command or its associated Scheme wrapper function mix add post hook command hook Function Adds a function to the list of pre hooks associated with the give command The arguments have the same meaning as in mix add pre hook mix add global pre hook hook Function mix add global post hook hook Function Global pre post hooks are executed before after any mixvm command or function wrapper invocation In this case hook takes two arguments a string with the name of the command being invoked and a string list with its arguments mix add break hook hook Function mix add cond break hook Function Add a hook funtion to be executed when an explicit resp conditional breakpoint is encountered during program execution hook is a function taking two arguments the Chapter 8 mixguile the Scheme virtual machine 69 source line number where the hook has occurred and the current program counter value The following code shows a simple definition and installation of a break hook define break hook lambda line address display Breakpoint at line display line d
99. n your report please include the version number which you can find by running mixasm version Also include in your message the output that the program produced and the output you expected Appendix A Copying 75 Appendix A Copying GNU MDK is distributed under the GNU General Public License GPL and this manual under the GNU Free Documentation License GFDL A 1 GNU General Public License Version 3 29 June 2007 Copyright 2007 Free Software Foundation Inc http fstf org Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed Preamble The GNU General Public License is a free copyleft license for software and other kinds of works The licenses for most software and other practical works are designed to take away your freedom to share and change the works By contrast the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program to make sure it remains free software for all its users We the Free Software Foundation use the GNU General Public License for most of our software it applies also to any other work released this way by its authors You can apply it to your programs too When we speak of free software we are referring to freedom not price Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software and charge for them if you wish
100. nd 9 or a defined symbol TERM if present the label must always start at the first column in its line for the first whitespace in the line maks the beginning of the second field an operation mnemonic which can represent either a MIX instruction OUT and HLT in lines 7 and 8 above or an assembly pseudoinstruction e g the ORIG pseudoinstruction in line 6 an optional operand for the pseudo instruction and an optional free text comment 1 Tf an ORIG directive is not used the program will be loaded by the virtual machine at address 0 ORIG allows allocating the executable code where you see fit 28 GNU MIX Development Kit mdk Lines 9 12 of the hello mixal file above also show the second and last difference between Knuth s MIXAL definition and ours the operand of the ALF pseudoinstruction a word of five characters must be quoted using The workings of this sample program should be straightforward if you are familiar with MIXAL See TAOCP vol 1 for a thorough definition or Chapter 2 MIX and MIXAL tutorial page 9 for a tutorial 3 2 Compiling Three simulators of the MIX computer called mixvm gmixvm and mixguile are included in the MDK tools They are able to run binary files containing MIX instructions written in their binary representation You can translate MIXAL source files into this binary form using mixasm the MIXAL assembler So in order to compile the hello mixal file you can type t
101. ne HLT END ST the contents of rA is set to 69 and not to 2001 An specially tricky case occurs when using local symbols in conjunction with ORIG pseudoinstructions To wit ORIG 1999 ST NOP 3H CON 10 ENT1 LDA 3B rI1 is 2001 rA is 10 So far so good 3H ORIG 3B 1000 at this point 3H equals 2003 and the location counter equals 3000 ENT2 LDX 3B rI2 contains 3000 rX contains 2003 HLT END ST 2 2 6 Literal constants MIXAL allows the introduction of literal constants which are automatically stored in mem ory addresses after the end of the program by the assembler Literal constants are denoted as wexp where wexp is a w expression see Section 2 2 4 W expressions page 22 For instance the code L EQU 5 LDA 20 L 7 The author wants to thank Philip E King for pointing these two special cases of local symbol usage to him Chapter 2 MIX and MIXAL tutorial 25 causes the assembler to add after the program s end an instruction with contents 15 20 L and to assemble the above code as the instruction LDA a where a stands for the address in which the value 15 is stored In other words the compiled code is equivalent to the following L EQU 5 LDA a a CON 20 L END start Chapter 3 Getting started 27 3 Getting started In this chapter you will find a sample code compile run debug session using the MDK util ities Familiarity with the MIX mythical computer and its asse
102. nted in the previous section by adding error checking 4 usr bin mixguile e main s E Execute a given program and print the registers define main lambda args load the file provided as a command line argument mix load cadr args execute it if mix load succeeded if mix last result mix run print the contents of registers if the above commands succeded if mix last result mix pall Please refer to Section 6 2 Commands page 48 for a list of available commands Given the description of a mixvm it is straightforward to use its Scheme counterpart and there fore we shall not give a complete description of these functions here Instead we will only mention those wrappers that exhibit a treatment of their differing from that of their command counterpart mix preg register Function mix sreg register value Function The argument register of these functions can be either a string or a symbol repre senting the desired register For instance the following invocations are equivalent mix preg I1 mix preg I1 mix pmem from to Function The command pmem takes a single argument which can be either a cell number or a range of the form FROM TO This function takes one argument to ask for a single memory cell contents or two parameters to ask for a range For instance the following commands are equivalent MIX gt pmem 10 12 0010 00 00 00 00 00 0000000000 0011 00 00 00 00 00
103. ntents of the memory cell with address FROM is printed as in MIX gt pmem 3000 3000 46 58 00 19 37 0786957541 MIX gt The memory contents is displayed both as the set of five MIX bytes plus sign com posing the stored MIX word and between parenthesis the decimal representation of the module of the stored value smem sets the content of the memory cell with address address to value expressed as a decimal constant 56 GNU MIX Development Kit mdk 6 2 4 Configuration commands This section describes commands that allow you to configure the virtual machine behaviour This configuration is stored in the MDK directory mdk As you can see in their description some commands print as a side effect informa tional messages to the standard output e g load prints a message telling you the loaded program s start address these messages can be enabled disabled using slog slog onl off config command Turns on off the logging of informational messages Note that error messages are always displayed as well as state messages required using commands prefixed with p preg pmem and the like stime onloff config command ptime config command The stime command un sets the printing of timing statistics and ptime prints their current value MIX gt ptime Elapsed time 10 Total program time 11 Total uptime 11 MIX gt sedit TEMPLATE config command pedit config command sedit sets the command to be used to e
104. ny other output device a file named according to the following table will be created and the specified MIX words will be written to the file in binary form for binary devices or in ASCII for char devices Files corresponding to input block devices should be created and filled beforehand to be used by the MIX virtual machine for input output devices this creation can be accomplished by a MIXAL program writing to the device the required data or if you prefer with your favourite editor The device files are stored by default in the directory mdk this location can be changed using the mixvm command devdir see Section 6 2 4 Configuration commands page 56 Device No filename type and block size Tape 0 7 tape 0 7 dev bin i o 100 words Disks 8 15 disk 0 7 dev bin i o 100 words Card reader 16 cardrd dev char in 16 words Card writer 17 cardwr dev char out 16 words 58 GNU MIX Development Kit mdk Line printer 18 printer dev char out 24 words Terminal 19 stdin stdout char i o 14 words Paper tape 20 paper dev char in 14 words Devices of type char are stored as ASCII files using one line per block For instance since the card reader has blocks of size 16 that is 80 characters it will be emulated by an ASCII file consisting of lines with length 80 If the reader finds a line with less than the required number of characters it pads the memory with zeroes MIX character space to complete the
105. of MDK s user interface Sergey Poznyakoff provided patches to mixlib mix scanner improving MIXAL com pliance Francesc Xavier Noria kindly and thoroughly reviewed the MDK documentation pro viding insightful advice Eric S Raymond contributed the documentation file MIX DOC and the samples elevator mixal and mistery mixal from his MIXAL package Nelson H F Beebe has tested MDK in a lot of Unix platforms suggesting portability enhancements to the source code Ryan Schmidt Agustin Navarro Ying Chieh Liao Adrian Bunk Baruch Even and Ronald Cole ported MDK to different platforms and created and or maintain packages for it Jason Uhlenkott Andrew Hood Radu Butnaru Ruslan Batdalov WeiZheng Sascha Wilde Michael Vernov and Xiaofeng Zhao reported bugs and suggested fixes to them Eli Bendersky Milan Bella and Jens Seidel reported bugs on the documentation Christoph von Nathusius Stephen Ramsay and Johan Swanljung tested MDK on dif ferent platforms and helped fixing the configuration process in them Richard Stallman suggested various improvements to the documentation and has always kept an eye on each MDK release MDK was inspired by Darius Bacon s MIXAL program Chapter 1 Installing MDK 5 1 Installing MDK 1 1 Download the source tarball GNU MDK is distributed as a source tarball available for download in the following URLs e ftp ftp gnu org pub gnu mdk e GNU mirrors The above sites contain the latest stable rele
106. of block devices To that end you have at your disposal the following instructions IN OUT IOC JRED Transfer a block of words from the specified unit to memory starting at address M OPCODE 36 MOD I O unit Transfer a block of words from memory starting at address M to the specified unit OPCODE 37 MOD I O unit Perfom a control operation given by M on the specified unit OPCODE 35 MOD I O unit Jump to M if the specified unit is ready OPCODE 38 MOD I O unit Chapter 2 MIX and MIXAL tutorial 17 JBUS Jump to M if the specified unit is busy OPCODE 34 MOD I O unit In all the above instructions the MOD subfile must be in the range 0 20 since it denotes the operation s target device The IOC instruction only makes sense for tape devices MOD 0 7 or 20 it shifts the read write pointer by the number of words given by M if it equals zero the tape is rewound 2 1 2 9 Conversion operators The following instructions convert between numerical values and their character represen tations NUM Convert rAX assumed to contain a character representation of a number to its numerical value and store it in rA OPCODE 5 MOD 0 CHAR Convert the number stored in rA to a character representation and store it in rAX OPCODE 5 MOD 1 Digits are represented in MIX by the range of values 30 39 digits 0 9 Thus if the contents of rA and rX are for ins
107. ommunicates with the external world by a set of input output devices which can be connected to it The computer interchanges informa tion using blocks of words whose length depends on the device at hand see Section 6 3 Devices page 57 These words are interpreted by the device either as binary information for devices 0 16 or as representing printable characters devices 17 20 In the last case each MIX byte is mapped onto a character according to the following table 00 01 A 02 B 03 C 00 D 05 E 06 F 07 G 08 H 09 I 10 11 J 12 K 13 L 14 M 15 N 16 O 17 P 18 Q 19 R 20 21 22 S 23 T 24 U 25 V 26 W 27 X 28 Y 29 Z 30 0 31 1 32 2 33 3 34 4 35 5 36 6 37 7 38 8 39 9 40 41 42 43 44 45 46 47 48 49 50 lt 51 gt 52 Q 53 54 55 The value 0 represents a whitespace The characters and correspond to symbols not representable as ASCII characters uppercase delta sigma and gamma respectively and byte values 56 63 have no associated character Finally the MIX computer features a virtual CPU which controls the above components and which is able to execute a rich set of instructions constituting its machine language similar to those commonly found in real CPUs including arithmetic logical storing com parison and jump instructions Being a typical von Neumann computer the MIX CPU fetchs binary instructions from memory sequentially unless a jump instruction is found and stores the address of
108. or the program counter using mix loc guile mix cell 3000 786957541 guile mix loc 3002 guile Other functions returning the contents of the virtual machine components are mix cmp and mix over which eval to the value of the comparison flag and the overflow toggle respectively For a complete list of these additional functions See Chapter 8 mixguile page 65 In the next section we ll see a sample of using these functions to extend mixguile s functionality Chapter 3 Getting started 35 3 4 3 Defining new functions Scheme is a powerful language and you can use it inside mixguile to easily extend the MIX interpreter s capabilities For example you can easily define a function that loads a file prints its name executes it and finally shows the registers contents all in one shot guile gt define my load and run RET lambda file RET mix load file RET display File loaded RET mix pprog RET mix run RET mix preg RET guile gt and use it to run your programs guile gt my load and run hello Program loaded Start address 3000 File loaded hello mix Running MIXAL HELLO WORLD done Elapsed time 11 Total program time 11 Total uptime 33 rA 00 00 00 00 00 0000000000 rX 00 00 00 00 00 0000000000 rJ 00 00 0000 rli 00 00 0000 rI2 00 00 0000 rI3 00 00 0000 rI4 00 00 0000 rI5 00 00 0000 rI6 00 00 0000 guile gt Or maybe you want a function wh
109. otient of the ten byte number A 00 00 00 00 00 that is A right padded with 5 null bytes or what amounts to the same multiplied by 64 to the fifth power divided by B Sample expressions are 18 8 3 30 14 324 1 3 11 4 11 43 1 64 01 00 00 00 00 00 00 00 00 01 00 01 00 00 OO 00 Note that all MIXAL expressions evaluate to a MIX word by definition All symbols appearing within an expression must be previously defined Future references are only allowed when appearing standalone or modified by an unary operator in the ADDRESS part of a MIXAL instruction e g OK stand alone future reference STA S1 1 5 ERROR future reference in expression LDX 2 81 EN LD1 2000 2 2 4 W expressions Besides expressions as described above see Section 2 2 3 Expressions page 22 the MIXAL assembler is able to handle the so called w expressions as the operands of the directives ORIG EQU CON and END see Section 2 2 2 MIXAL directives page 20 The general form of a w expression is the following Chapter 2 MIX and MIXAL tutorial 23 WEXP EXP CEXP WEXP where EXP stands for an expression and square brackets denote optional items Thus a w expression is made by an expression followed by an optional expression between parenthesis followed by any number of similar constructs separated by commas Sample w expressions are 2000 235 3 1 3 S2 3000 S1 82 3 5 23 W expressions are evaluated from left to r
110. ou When mixguile starts it looks for a file named mixguile scm in your MDK configuration directory mdk and if it exists loads it before entering the REPL Therefore you can copy your definitions in that file or load the functions scm file in nixguile scm 3 4 4 Hook functions Hooks are functions called before or after a given event occurs In mixguile you can define command and break hooks which are associated respectively with command execution and program interruption events The following sections give you a tutorial on using hook functions within mixguile 3 4 4 1 Command hooks In the previous section we have seen how to extend mixguile s functionality through the use of user defined functions Frequently you ll write new functions that improve in some way the workings of a built in mixvm command following this pattern a Prepare the command execution b Execute the desired command c Perform post execution operations We call the functions executed in step a pre hooks and those of step post hooks of the given command mixguile lets you specify pre and post hooks for any mixvm command using the mix add pre hook and mix add post hook functions which take as arguments a symbol naming the command and a function to be executed before resp after the command In other words mixguile will execute for you steps a and c above whenever you eval b The hook functions must take a single argument which is a string li
111. ou find problems with history readline functionality please try a newer manually installed readline version 8 GNU MIX Development Kit mdk e AMD Athlon GNU Linux version 2 4 2 2smp Red Hat 7 1 Seawolf N H F Beebe e Apple PowerPC G3 GNU Linux 2 2 18 4hpmac Red Hat Linux PPC 2000 Q4 N H F Beebe e DEC Alpha GNU Linux 2 2 19 6 2 1 Red Hat 6 2 N H F Beebe e Compaq DEC Alpha OSF 1 4 0F ONLY after adding rsync s snprintf implementa tion N H F Beebe e IBM PowerPC AIX 4 2 N H F Beebe e Intel Pentium III GNU Linux 2 4 9 31smp Red Hat 7 2 Enigma N H F Beebe e SGI Origin 200 IRIX 6 5 N H F Beebe e Sun SPARC GNU Linux 2 2 19 6 2 1 Red Hat 6 2 N H F Beebe e Sun SPARC Solaris 2 8 N H F Beebe MDK will probably work on any GNU Linux or BSD platform If you try it in a platform not listed above please send a mail to the author Chapter 2 MIX and MIXAL tutorial 9 2 MIX and MIXAL tutorial In the book series The Art of Computer Programming by D Knuth a virtual computer the MIX is used by the author together with the set of binary instructions that the virtual CPU accepts to illustrate the algorithms and skills that every serious programmer should master Like any other real computer there is a symbolic assembler language that can be used to program the MIX the MIX assembly language or MIXAL for short In the following subsections you will find a tutorial on these topi
112. overed work conveyed by you or copies made from those copies or b primarily for and in connection with specific products or compilations that contain the covered work unless you entered into that arrangement or that patent license was granted prior to 28 March 2007 Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law No Surrender of Others Freedom If conditions are imposed on you whether by court order agreement or otherwise that contradict the conditions of this License they do not excuse you from the conditions of this License If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations then as a consequence you may not convey it at all For example if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program Use with the GNU Affero General Public License Notwithstanding any other provision of this License you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work and to convey the resulting work 84 14 15 16
113. ow the alignment rules of the original MIXAL definition namely the ADDRESS must start at column 17 22 GNU MIX Development Kit mdk The above snippet also shows the use of a future reference that is the usage of a symbol MSG in the example prior of its actual definition The MIXAL assembler is able to handle future references subject to some limitations which are described in the following section see Section 2 2 3 Expressions page 22 Any line starting with an asterisk is treated as a comment and ignored by the assembler This is a comment this line is ignored This line is an error must be in column 1 As noted in the previous section comments can also be located after the OPERAND field of an instruction separated from it by white space as in LABEL LDA 100 This is also a comment 2 2 3 Expressions The ADDRESS INDEX and MOD fields of a MIXAL instruction can be expressions formed by numbers identifiers and binary operators and can also be used as unary operators Operator precedence is from left to right there is no other operator precedence rule and parentheses cannot be used for grouping A stand alone asterisk denotes the current memory location thus for instance 4 2 evaluates to 6 4 plus 2 times the current memory location White space is not allowed within expressions The special binary operator has the same meaning as in fspecs i e A B 8 A B while A B stands for the qu
114. pecified subfield is left padded with null bytes to complete a word Hence the MIX state after the instruction execution will be rI1 00 01 rI3 00 03 12 01 02 03 04 05 To further illustrate loading operators the following table shows the contents of rX after different LDX instructions LDX 12 0 0 rX 00 00 00 00 00 LDX 12 0 1 rX 00 00 00 00 0t LDX 12 3 5 rX 00 00 03 04 05 LDX 12 3 4 rX 00 00 00 03 04 LDX 12 0 5 rX 01 02 03 04 05 2 1 2 3 Storing operators The following instructions are the inverse of the load operations they are used to store a subfield of a register into a memory location Here MOD represents the subfield of the memory cell that is to be overwritten with bytes from a register These bytes are taken beginning by the rightmost side of the register STA Store rA OPCODE 24 MOD fspec V rA STX Store rX OPCODE 31 MOD fspec V rX STi Store rli OPCODE 24 i MOD fspec V rli STJ Store rJ OPCODE 32 MOD fspec V rJ STZ Store zero OPCODE 33 MOD fspec V 0 By way of example consider the instruction STA 1200 2 3 It causes the MIX to fetch bytes no 4 and 5 of register A and copy them to bytes 2 and 3 of memory cell no 1200 remember that for these instructions MOD specifies a subfield of the memory address The other bytes of the memory cell retain their values Thus i
115. point is around a MIXAL pseu doinstruction in your source file Emacs will recognize it and will suggest the right MIX operation code 1 mixal mode has been developed and documented by Pieter E J Pareit 44 GNU MIX Development Kit mdk 4 1 3 Compiling and running After you have written your MIXAL program you ll probably want to test it This can be done with the MIX virtual machine First you will need to compile your code into MIX byte code This can be done within Emacs with the command M x compile C c c In case of compilation errors you can jump to the offending source code line with M x next error Once the program compiles without errors you can debug or run it To invoke the debugger use M x mixal debug C c d Emacs will open a GUD buffer where you can use the debugging commands described in See Chapter 6 mixvm page 47 If you just want to execute the program you can do so with M x mixal run C c r This will invoke mixvm execute the program and show its output in a separate buffer 4 2 GUD integration If you are an Emacs user and write your MIXAL programs using this editor you will find the elisp program mixvm el quite useful mixvm el allows running the MIX virtual machine mixvm see Chapter 6 mixvm page 47 inside an Emacs GUD buffer while visiting the MIXAL source file in another buffer After installing mixvm el see Section 1 4 Emacs support page 6 you can initiate an MDK GUD session inside Emacs
116. ram reached at address 3002 Elapsed time 10 Total program time 11 Total uptime 11 MIX gt strace off MIX gt The executed instruction as it was translated is shown between square brackets after the memory address and following it you can see the actual MIXAL code that was compiled into the executed instruction The tracing behaviour is stored as a configuration parameter in mdk pline LINE NUMBER debug command Prints the requested source line or the current one if line number is omitted MIX gt load samples hello Program loaded Start address 3000 MIX gt pline Line 5 START OUT MSG TERM MIX gt pline 6 Line 6 HLT MIX gt pbt INS NUMBER debug command This command prints backtrace of executed instructions Its optional argument ins number is the number of instructions to print If it is omitted or equals zero all executed instructions are printed For instance if you compile and load the following program bt mixal ORIG O BEG JMP 1 JMP 1 FOO JMP BAR BAR HLT END BEG you could get the following traces MIX gt load bt Program loaded Start address 0 MIX gt next MIX gt pbt Chapter 6 mixvm the MIX computer simulator 53 HO BEG in bt mixal 2 MIX gt next MIX gt pbt HO 1 in bt mixal 3 1 BEG in bt mixal 2 MIX gt run Running done MIX gt pbt 3 HO BAR in bt mixal 5 1 FOO in bt mixal 4 2 1 in bt mixal 3 MIX gt pbt 0 BAR in bt mixal 5 1 FDO in bt mi
117. rd WORD must be expressed as a sign followed by five space delimited two digit decimal values representing the five bytes composing the word The reverse operation showing the word representation of a decimal value can be accomplished with weval For instance MIX gt w2d 01 00 00 02 02 16777346 MIX gt weval 16777346 01 00 00 02 02 0016777346 MIX gt 6 2 3 State commands Inspection and modification of the virtual machine state memory registers overflow toggle and comparison flag contents is accomplished using the following commands pstat state command This commands prints the current virtual machine state which can be one of the following No program loaded Program successfully loaded Execution stopped next executed Execution stopped breakpoint encountered Execution stopped conditional breakpoint encountered Program successfully terminated pc state command Prints the current value of the program counter which stores the address of the next instruction to be executed in a non halted program sreg A X J 1 1 6 value state command preg A X J 1 1 6 state command pall state command preg prints the contents of a given MIX register For instance preg A will print the contents of the A register When invoked without arguments all registers shall be printed MIX gt preg rA 00 00 00 00 35 0000000035 rX 00 00 00 15 40 0000001000 rJ
118. remain obligated to ensure that it is available for as long as needed to satisfy these requirements e Convey the object code using peer to peer transmission provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d A separable portion of the object code whose source code is excluded from the Cor responding Source as a System Library need not be included in conveying the object code work A User Product is either 1 a consumer product which means any tangible per sonal property which is normally used for personal family or household purposes or 2 anything designed or sold for incorporation into a dwelling In determining whether a product is a consumer product doubtful cases shall be resolved in favor of coverage For a particular product received by a particular user normally used refers to a typical or common use of that class of product regardless of the status of the par ticular user or of the way in which the particular user actually uses or expects or is expected to use the product A product is a consumer product regardless of whether SU GNU MIX Development Kit mdk the product has substantial commercial industrial or non consumer uses unless such uses represent the only significant mode of use of the product Installation Information for a User Product means any methods procedures aut
119. riate copyright notice for your modifications adjacent to the other copyright notices Include immediately after the copyright notices a license notice giving the public permission to use the Modified Version under the terms of this License in the form shown in the Addendum below Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document s license notice Include an unaltered copy of this License Preserve the section Entitled History Preserve its Title and add to it an item stating at least the title year new authors and publisher of the Modified Version as given on the Title Page If there is no section Entitled History in the Docu ment create one stating the title year authors and publisher of the Document as given on its Title Page then add an item describing the Modified Version as stated in the previous sentence Preserve the network location if any given in the Document for public access to a Transparent copy of the Document and likewise the network locations given in the Document for previous versions it was based on These may be placed in the History section You may omit a network location for a work that was published at least four years before the Document itself or if the original publisher of the version it refers to gives permission For any section Entitled Acknowledgements or Dedications Preserve the Title of the section an
120. rks provided that you comply with the terms of this License in conveying all material for which you do not control copyright Those thus making or running the covered works for you must do so exclusively on your behalf under your direction and control on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you Conveying under any other circumstances is permitted solely under the conditions stated below Sublicensing is not allowed section 10 makes it unnecessary 3 Protecting Users Legal Rights From Anti Circumvention Law 78 GNU MIX Development Kit mdk No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996 or similar laws prohibiting or restricting circumvention of such measures When you convey a covered work you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work and you disclaim any intention to limit operation or modification of the work as a means of enforcing against the work s users your or third parties legal rights to forbid circumvention of technological measures Conveying Verbatim Copies You may convey verbatim copies of the Program s source code as you receive it in any med
121. s are available they will be shown in the echo area Thus typing p TAB will produce the following output on the echo area Completions pc psym preg pflags pall pmem which lists all the available commands starting with p In addition the command prompt maintains a history of typed commands which can be recovered using the arrow up and down keys As mentioned above a file containing previous sessions commands is stored in the configuration directory mdk and reloaded every time you start gmixvm You can change the font used to display the issued commands and the mes sages in the echo area using the Settings gt Change font gt Command prompt and Settings gt Change font gt Command log menu commands 7 3 MIX virtual machine The first notebook s page displays the current status of the virtual machine There you can find the registers contents the value of the comparison and overflow flags the loca tion pointer a list with all MIX memory cells and their contents and the time statistics including total uptime elapsed time since the last run command and total execution time for the currently loaded MIX program If you click any register entry you will be prompted for a new register s contents In the same manner click on any address of the memory cells list to be prompted for the new contents of the clicked cell If you click the address column s title a dialog asking you for a memory address will appear if you introd
122. ssible values are the scheme symbols L lesser E equal and G greater mix up time Function Evaluates to the current virtual machine uptime mix lap time Function Evaluates to the current virtual machine lapsed time i e the time elapsed since the last run or next command mix prog time Function Evaluates to the total time spent executing the currently loaded program mix prog name Function Evaluates to a string containing the basename without any leading path of the currently loaded MIX program mix prog path Function Evaluates to a string containing the full path to the currently loaded MIX program Chapter 8 mixguile the Scheme virtual machine 71 mix src path Function Evaluates to a string containing the full path to the source file of the currently loaded MIX program mix src line lineno Function mix src line no Function mix src line no evaluates to the current source file number during the execution of a program mix src line evaluates to a string containing the source file line number lineno when invoked without argument it evaluates to mix src line mix src line no mix ddir Function Evaluates to a string containing the full path of the current device directory Chapter 9 Reporting Bugs T3 9 Reporting Bugs If you have any questions comments or suggestions please send electronic mail to the author If you find a bug in MDK please send electronic mail to the MDK bug list I
123. st of Chapter 3 Getting started 37 the command s arguments As an example let us define the following hooks for the next command define next pre hook lambda arglist mix slog f define next post hook lambda arglist display Stopped at line display mix src line no display display mix src line newline mix slog t In these functions we are using the function mix slog to turn off the informational messages produced by the virtual machine since we are providing our own ones in the post hook function To install these hooks we would write mix add pre hook nert next pre hook mix add post hook next next post hook Assuming we have put the above expressions in mixguile s initialisation file we would obtain the following results when evaluating mix next guile gt mix next MIXAL HELLO WORLD Stopped at line 6 HLT guile As a second more elaborated example let s define hooks which print the address and contents of a cell being modified using smem The hook functions could be something like this define smem pre hook lambda arglist if eq length arglist 2 begin display Changing address display car arglist newline display Old contents display mix cell string number car arglist newline error Wrong arguments arglist define smem post hook lambda arglist if eq length arglist 2 begin display New contents
124. t obtaining 00 01 00 00 00 and afterwards take two bytes from 66 01 and 02 and store them as bytes 4 and 5 of the result obtaining 00 01 00 01 02 262210 The process is repeated for each new comma separated example For instance 1 1 1 2 2 2 3 3 3 4 4 4 01 02 03 04 00 As stated before w expressions can only appear as the operands of MIXAL directives taking a constant value ORIG EQU CON and END Future references are not allowed within w expressions i e all symbols appearing in a w expression must be defined before it is used 2 2 5 Local symbols Besides user defined symbols MIXAL programmers can use the so called local symbols which are symbols of the form 1 9 HBF A local symbol nB refers to the address of the last previous occurrence of nH as a label while nF refers to the next nH occurrence Unlike 24 GNU MIX Development Kit mdk user defined symbols nH can appear multiple times in the LABEL part of different MIXAL instructions The following code shows an instance of local symbols usage line 1 1H LDA 100 line 2 1B refers to address of line 1 3F refers to address of line 4 STA 3F 2 1B 2 line 3 redefinition of 1H 1H STZ line 4 1B refers to address of line 3 3H JMP 1B Note that a B local symbol never refers to a definition in its own line that is in the following program ORIG 1999 ST NOP 3H EQU 69 3H ENTA 3B Local symbol 3B refers to 3H in previous li
125. t to the section titles in the list of Invariant Sections in the license notice of the combined work In the combination you must combine any sections Entitled History in the vari ous original documents forming one section Entitled History likewise combine any sections Entitled Acknowledgements and any sections Entitled Dedications You must delete all sections Entitled Endorsements COLLECTIONS OF DOCUMENTS You may make a collection consisting of the Document and other documents released under this License and replace the individual copies of this License in the various documents with a single copy that is included in the collection provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects You may extract a single document from such a collection and distribute it individu ally under this License provided you insert a copy of this License into the extracted document and follow this License in all other respects regarding verbatim copying of that document AGGREGATION WITH INDEPENDENT WORKS A compilation of the Document or its derivatives with other separate and independent documents or works in or on a volume of a storage or distribution medium is called Appendix A Copying 91 10 an aggregate if the copyright resulting from the compilation is not used to limit the legal rights of the compilation s users beyond what the individual works p
126. t cover and Back Cover Texts on the back cover Both covers must also clearly and legibly identify you as the publisher of these copies The front cover must present the full title with all words of the title equally prominent and visible You may add other material on the covers in addition Copying with changes limited to the covers as long as they preserve the title of the Document and satisfy these conditions can be treated as verbatim copying in other respects If the required texts for either cover are too voluminous to fit legibly you should put the first ones listed as many as fit reasonably on the actual cover and continue the rest onto adjacent pages If you publish or distribute Opaque copies of the Document numbering more than 100 you must either include a machine readable Transparent copy along with each Opaque copy or state in or with each Opaque copy a computer network location from which the general network using public has access to download using public standard network protocols a complete Transparent copy of the Document free of added material If you use the latter option you must take reasonably prudent steps when you begin distribution of Opaque copies in quantity to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy directly or through your agents or retailers of that edition to the public It is requested
127. tance rA 30 30 31 32 33 rX 31 35 39 30 34 the represented number is 0012315904 and NUM will store this value in rA De we end up with rA 0 46 62 52 0 12315904 If any byte in rA or rB does not belong to the range 30 39 it is interpreted by NUM as the digit obtained by taking its value modulo 10 E g values 0 10 20 30 40 50 60 all represent the digit 0 2 12 22 etc represent the digit 2 and so on For instance the number 0012315904 mentioned above could also be represented as rA 10 40 31 52 23 rX 11 35 49 20 54 CHAR performs the inverse operation using only the values 30 to 39 for representing digits 0 9 2 1 2 10 Shift operators The following instructions perform byte wise shifts of the contents of rA and rt SLA SRA SLAX SRAX SLC SRC Shift rA or rAX left right or rAX circularly see example below left or right M specifies the number of bytes to be shifted OPCODE 6 MOD 0 1 2 3 4 5 3 In Knuth s original definition there are other control operations available but they do not make sense when implementing the block devices as disk files as we do in MDK simulator For the same reason MDK devices are always ready since all input output operations are performed using synchronous system calls 18 GNU MIX Development Kit mdk If we begin with say rA 01 02 03 04 05 we would have the following modifica
128. terms a Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License or Appendix A Copying 81 b Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it or c Prohibiting misrepresentation of the origin of that material or requiring that mod ified versions of such material be marked in reasonable ways as different from the original version or d Limiting the use for publicity purposes of names of licensors or authors of the material or e Declining to grant rights under trademark law for use of some trade names trade marks or service marks or f Requiring indemnification of licensors and authors of that material by anyone who conveys the material or modified versions of it with contractual assumptions of liability to the recipient for any liability that these contractual assumptions directly impose on those licensors and authors All other non permissive additional terms are considered further restrictions within the meaning of section 10 If the Program as you received it or any part of it con tains a notice stating that it is governed by this License along with a term that is a further restriction you may remove that term If a license document contains a further restriction but permits relicensing or conveying under this License you may add to a covered
129. the MIX virtual machine will be available in your system You can invoke it by typing gmixvm vhuq version help usage noinit at your command prompt where the options have the following meanings V User Option version User Option Prints version and copyleft information and exits h User Option help User Option u User Option usage User Option Prints a summary of available options and exits mel User Option noinit User Option Do not load the Guile initialisation file mdk mixguile scm at startup This file contains any local Scheme code to be executed by the embedded Guile interpreter at startup see Section 3 5 Using Scheme in mixvm and gmixvm page 40 Typing gmixvm or gmixvm q at your command prompt the main window will appear offering you a graphical interface to run and debug your MIX programs Apart from the menu and status bars we can distinguish two zones or halves in this main window In the upper half of gmixvm s main window there is a notebook with three pages namely e a MIX virtual machine view which shows you the registers flags memory contents and time statistics of the virtual machine e a MIXAL source view which shows the MIXAL file and lets you manage breakpoints e a Devices view which shows you the output to character based MIX block devices These three windows can be detached from the notebook using either the penultimate toolbar button which detachs
130. the next instruction to be executed in an internal register called location counter also known as program counter in other architectures Chapter 2 MIX and MIXAL tutorial 11 The next section See Section 2 1 2 MIX instruction set page 11 gives a complete description of the available MIX binary instructions 2 1 2 MIX instruction set The following subsections fully describe the instruction set of the MIX computer We begin with a description of the structure of binary instructions and the notation used to refer to their subfields The remaininig subsections are devoted to describing the actual instructions available to the MIX programmer 2 1 2 1 Instruction structure MIX instructions are codified as words with the following subfield structure Subfield fspec Description ADDRESS 0 2 The first two bytes plus sign are the address field Com bined with the INDEX field denotes the memory address to be used by the instruction INDEX 3 3 The third byte is the index normally used for indexing the address MOD 4 4 Byte four is used either as an operation code modifier or as a field specification OPCODE 5 5 The last least significant byte in the word denotes the operation code or graphically ADDRESS INDEX MOD OPCODE 6 For a given instruction M stands for the memory address obtained after indexing the ADDRESS subfield using its INDEX byte and V is the contents of the subfield indicat
131. tions to rA contents when performing the instructions on the left column SLA 2 rA 03 04 05 00 00 SLA 6 rA 00 00 00 00 00 SRA 1 rA 00 01 02 03 04 Note that the sign is unaffected by shift operations On the other hand SLC SRC SLAX and SRAX treat rA and rX as a single 10 bytes register ignoring again the signs For instance if we begin with rA 01 02 03 04 05 and rX 06 07 08 09 10 we would have SLC 3 rA 04 05 06 07 08 rX 09 10 01 02 03 SLAX3 rA 0405 06 0708 rX 09 10 00 00 00 SRC 4 rA 07 08 091001 rX 02 03 04 05 06 SRAX4 rA 0000 0000 01 rX 02 03 04 05 06 2 1 2 11 Miscellaneous operators Finally we list in the following table three miscellaneous MIX instructions which do not fit in any of the previous subsections MOVE Move MOD words from M to the location stored in rll OPCODE 7 MOD no of words NOP No operation OPCODE 0 MOD 0 HLT Halt Stops instruction fetching OPCODE 5 MOD 2 The only effect of executing NOP is increasing the location counter while HLT usually marks program termination 2 1 2 12 Execution times When writing MIXAL programs or any kind of programs for that matter whe shall often be interested in their execution time Loosely speaking we will interested in the answer to the question how long takes a program to execute Of course this exe
132. twork Corresponding Source conveyed and Installation Information provided in accord with this section must be in a format that is publicly documented and with an implementa tion available to the public in source code form and must require no special password or key for unpacking reading or copying Additional Terms Additional permissions are terms that supplement the terms of this License by mak ing exceptions from one or more of its conditions Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License to the extent that they are valid under applicable law If additional permis sions apply only to part of the Program that part may be used separately under those permissions but the entire Program remains governed by this License without regard to the additional permissions When you convey a copy of a covered work you may at your option remove any additional permissions from that copy or from any part of it Additional permissions may be written to require their own removal in certain cases when you modify the work You may place additional permissions on material added by you to a covered work for which you have or can give appropriate copyright permission Notwithstanding any other provision of this License for material you add to a covered work you may if authorized by the copyright holders of that material supplement the terms of this License with
133. uce a valid address this will be the first cell displayed in the scrollable list after you click the OK button The register contents are shown as a list of MIX bytes plus sign If you place the mouse pointer over any of them the decimal value of this MIX word will appear inside a tooltip Chapter 7 gmixvm the GTK virtual machine 61 You can change the font used to display the MIX virtual machine contents using the Settings gt Change font gt MIX menu command 7 4 MIXAL source view The second notebook s page dubbed Source shows you the MIXAL source of the currently loaded MIX file The information is presented in four columns The first column displays little icons showing the current program pointer and any set breakpoints The second and third columns show the address and memory contents of the compiled MIX instruction while the last one displays its corresponding MIXAL representation together with the source file line number You can set unset breakpoints by clicking on any line that has an associated memory address You can change the font used to display the MIXAL source code using the Settings gt Change font gt MIXAL menu command 7 5 MIX devices view The last notebook page dubbed Devices shows you the output input to from MIX block devices the console line printer paper tape disks card and tapes see Section 6 3 Devices page 57 produced by the running program Input device contents is read from files locate
134. urrent address 3000 MIX gt next MIXAL HELLO WORLD Elapsed time 1 Total program time 1 Total uptime 1 MIX gt pc Current address 3001 MIX gt next End of program reached at address 3002 32 GNU MIX Development Kit mdk Elapsed time 10 Total program time 11 Total uptime 11 MIX gt pc Current address 3002 MIX gt next MIXAL HELLO WORLD Elapsed time 1 Total program time 1 Total uptime 12 MIX gt MIX gt run Running done Elapsed time 10 Total program time 11 Total uptime 22 MIX gt As an aside the above sample also shows how the virtual machine handles cummulative time statistics and automatic program restart You can set a breakpoint at a given address using the command sbpa set breakpoint at address When a breakpoint is set run will stop before executing the instruction at the given address Typing run again will resume program execution Coming back to our hello world example we would have MIX gt sbpa 3001 Breakpoint set at address 3001 MIX gt run Running MIXAL HELLO WORLD Stopped breakpoint at line 8 address 3001 Elapsed time 1 Total program time 1 Total uptime 23 MIX gt run Running done Elapsed time 10 Total program time 11 Total uptime 33 MIX gt Note that since we compiled hello mixal with debug info enabled the virtual machine is able to tell us the line in the source file corresponding to the breakpoint we are setting As a m
135. version but do not include claims that would be infringed only as a consequence of further modification of the contributor version For purposes of this definition con trol includes the right to grant patent sublicenses in a manner consistent with the requirements of this License Each contributor grants you a non exclusive worldwide royalty free patent license under the contributor s essential patent claims to make use sell offer for sale import and otherwise run modify and propagate the contents of its contributor version In the following three paragraphs a patent license is any express agreement or com mitment however denominated not to enforce a patent such as an express permission to practice a patent or covenant not to sue for patent infringement To grant such Appendix A Copying 83 12 13 a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party If you convey a covered work knowingly relying on a patent license and the Corre sponding Source of the work is not available for anyone to copy free of charge and under the terms of this License through a publicly available network server or other readily accessible means then you must either 1 cause the Corresponding Source to be so available or 2 arrange to deprive yourself of the benefit of the patent license for this particular work or 3 arrange in a manner consistent with the requir
136. with their values will appear in the status bar Chapter 8 mixguile the Scheme virtual machine 65 8 mixguile the Scheme virtual machine This chapter provides a reference to using mixguile and the Scheme function library giving access to the MIX virtual machine in the MDK emulators mixguile mixvm and gmixvm See Section 3 4 Using mixguile page 33 for a tutorial step by step introduction to mixguile and using Scheme as an extension language for the MDK MIX virtual machines 8 1 Invoking mixguile Invoking mixguile without arguments will enter the Guile REPL read eval print loop after loading if it exists the user s initialisation file mdk mixguile scm mixguile accepts the same command line options than Guile mixguile s SCRIPT c EXPR 1 FILE e FUNCTION qhv help version The meaning of these options is as follows h User Option help User Option Prints usage summary and exits V User Option version User Option Prints version and copyleft information and exits s SCRIPT User Option Loads Scheme code from script evaluates it and exits This option can be used to write executable Scheme scripts as described in Section 3 4 5 Scheme scripts page 39 c EXPR User Option Evaluates the given Scheme expression and exits 1 FILE User Option Loads the given Scheme file and enters the REPL read eval print loop e FUNCTION User Option After reading the script execut
137. with this program If not see http www gnu org licenses Also add information on how to contact you by electronic and paper mail If the program does terminal interaction make it output a short notice like this when it starts in an interactive mode program Copyright C year name of author This program comes with ABSOLUTELY NO WARRANTY for details type show w This is free software and you are welcome to redistribute it under certain conditions type show c for details The hypothetical commands show w and show c should show the appropriate parts of the General Public License Of course your program s commands might be different for a GUI interface you would use an about box You should also get your employer if you work as a programmer or school if any to sign a copyright disclaimer for the program if necessary For more information on this and how to apply and follow the GNU GPL see http www gnu org licenses The GNU General Public License does not permit incorporating your program into proprietary programs If your program is a subroutine library you may consider it more useful to permit linking proprietary applications with the library If this is what you want to do use the GNU Lesser General Public License instead of this License But first please read http www gnu org philosophy why not lgpl html 86 GNU MIX Development Kit mdk A 2 GNU Free Documentation License Version 1 2 Nov
138. xal 4 2 1 in bt mixal 3 3 BEG in bt mixal 2 MIX gt Note that the executed instruction trace gives you the label of the executed line or if it has no label its address As you have probably observed mixvm prints timing statistics when running programs This behaviour can be controlled using the stime command see Section 6 2 4 Configuration commands page 56 mixvm is also able of evaluating w expressions see Section 2 2 4 W expressions page 22 using the following command weval WEXP debug command Evaluates the given w expression WEXP The w expression can contain any cur rently defined symbol For instance MIX gt psym START 00 00 00 46 56 0000003000 MIX gt weval START 0 1 START 3 4 56 00 46 56 00 0939716096 MIX gt New symbols can be defined using the ssym command ssym SYM WEXP debug command Defines the symbol named SYM with the value resulting from evaluating WEXP an w expression The newly defined symbol can be used in subsequent weval commands as part of the expression to be evaluated E g MIX gt ssym S 2 23 START 00 00 18 19 56 0000075000 MIX gt psym S 00 00 18 19 56 0000075000 MIX gt weval S 3 4 54 GNU MIX Development Kit mdk 00 00 19 56 00 0000081408 MIX gt Finally if you want to discover which is the decimal value of a MIX word expressed as five bytes plus sign you can use w2d WORD debug command Computes the decimal value of the given wo
139. y local law that Appendix A Copying 85 most closely approximates an absolute waiver of all civil liability in connection with the Program unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee END OF TERMS AND CONDITIONS How to Apply These Terms to Your New Programs If you develop a new program and you want it to be of the greatest possible use to the public the best way to achieve this is to make it free software which everyone can redistribute and change under these terms To do so attach the following notices to the program It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty and each file should have at least the copyright line and a pointer to where the full notice is found one line to give the program s name and a brief idea of what it does Copyright C year name of author This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 3 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along

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