New version of the ICWS'94 draft
Planar
detailed comments yet, we need somebody to write the pspace stuff (and
the multi-line EQU and FOR/ROF as well). I'll try to post a summary
of past debates on read/write distance before the end of the week.
____________ cut here ________________
Annotated Draft of the Proposed 1994 Core War Standard.
Version 3.3
Annotated Draft Last Modified: November 8, 1995
Last modified by: Damien Doligez
Base draft by: Mark Durham
[Planar's intro to ver. 3.3]
This is a list of what I've changed from version 3.2:
+ Changed "pointer counter" to "program counter" in Mark's intro.
+ Changed "A-pointer" and "B-pointer" to "A-number" and "B-number" in
Mark's intro
+ Added A-number indirect, A-number predecrement, and A-number
postincrement to the description of addressing modes. Changed
"indirect", "predecrement", and "postincrement" to "B-number indirect",
etc.
+ Clarified the fact that newlines are not considered whitespace.
+ Added the SEQ, SNE, and NOP opcodes
+ Changed a reference to "load file" into "assembly file" in section 2.3
+ Simplified the grammar entries for label_list and newline.
+ Removed the grammar entries for list, simplified those for files.
+ Stop parsing (not simply assembling) after the END.
+ Added predefined labels.
+ Added ";assert" comment convention.
+ Specified the behaviour of {DIV,MOD}.{I,F,X} when a component of the
A-value is 0.
+ Fixed a discrepancy between the text and the sample code on the
behavior of JMN and DJN, >>>BY CHANGING THE TEXT<<<. The old version
would not jump (for JMN.F and DJN.F) if either field of the target
was zero.
+ Added SEQ as a synonym to CMP (in description and code)
+ Added SNE (in description and code)
+ Added NOP (in description and code)
+ Specified the behavior of SLT.F
+ Fixed the bug with label "noqueue" in the ARITH_DIV macro.
+ Updated the conversion tables.
+ Updated the list of new opcodes and addressing modes.
This is a list of things to do:
+ Decide on whether to remove read/write distance.
+ Add ROUNDS and PSPACE and LDP and STP.
+ Define "battle" and "rounds" in the glossary.
+ The assembler and run-time environment must agree on the value of
predefined labels. Make this fact explicit.
+ Add CURLINE and VERSION.
+ Decide which one takes precedence if the description and code
disagree and write this decision explicitely in the standard.
+ Add the comparison and logical operators to the description and
to the grammar of expressions.
+ Specify the operator precedence for expressions (if only by saying
it's the same as in the C language).
+ Add multi-line EQUs and FOR/ROF macros.
[Stefan's intro to ver. 3.2]
The sample simulator was rewritten extensively based on suggestions by Damien
Doligez ("Planar") and on our experience implemementing the pMARS, the first
ICWS'94 simulator. Thanks to Planar and also Steven Morrell for pointing out
many omission and ambiguities in the previous revision. Other readers of
rec.games.corewar have also provided many helpful comments.
Changes incorporated since last revision:
Text:
- corrected various typos
- clarified behaviour of JMN, JMZ and DJN with .F modifier
- defined behavior for division by zero
- incorporated EOF in grammar, eliminated "empty" expression
- limited definition of whitespace to <space> and <tab>
- labels are case sensitive
- "pointer counter" -> "program counter"
- added default modifier rules (A.2.1.1-2)
Sample code:
- macro'ized ADD/SUB/MUL/DIV code
- test for division by zero
- .AB in JMZ, JMN, DJN works now like .B; .BA like .A
- fixed DJN.F, JMN.F
To do for next revision:
- fix formal grammar (still flaky)
- exclude/redefine read/write limits, add jump limit?
[Mark's intro to ver. 3.1]
The information presented here is not part of the Draft proper. The Draft
proper immediately follows these annotations, beginning with the line
"0001 Draft of Proposed 1994 Core War Standard". The content lines of the
Draft proper are numbered for easy reference. The numbers may or may not
be included in the final Draft.
Internal annotations were removed to clean-up the draft for presentation to
the ICWS for comment. These annotations which precede the draft take their
place.
Open-ended references were removed to clean-up the draft for presentation
to the ICWS for comment. The question of the inclusion or exclusion of
various opcodes, modes, etc. has not been closed as of yet. Such additions
or deletions should be finalized by the next draft however.
Previously speculative references were either included or removed to
clean-up the draft for presentation to the ICWS for comment. See above.
The Load File section was rewritten to aid in the readability of load
files. It was deemed best that Load Files be a subset of Assembly Files;
therefore Load Files should logically follow the Assembly File section.
For that reason, the two sections have been swapped.
Example MARS code is now included. Other parts of the standard, such as
validation, remain incomplete. The remaining incomplete sections do not
impact on the other sections of the standard and so can be completed even
after consideration of the rest of the draft by the ICWS. Alternatively,
they could be issued as separate documents.
The MARS code is specifically designed to mirror the draft as closely as
possible. There is a multitude of optimizations which could have been
made but were not in order that the example code could serve as a
possible clarification of obscure parts of the draft. Do not suggest
changes to the example code which speed up processing at the expense of
mirroring the draft.
Several changes have been made with the goal of expanding the flexibility
of Core War without compromising backwards compatibility and without
seriously altering the nature of the game. In that vein:
The modulus '%' operator was added to the Assembly File section.
Read and Write limitations with folding have been clarified. These limits
allow the possibility of warriors essentially running in a mini-core inside
core, folding out-of-bounds access attempts back into accessible memory.
The main advantages to folding are: old-style bombers like Dwarf do not
unfairly and unknowingly spend cycles doing nothing, and movement to seek
and destroy enemy warriors is still encouraged by the limits. The main
disadvantage is that limits which are not factors of the size of core lead
to unexpected results. Example: a reference to address location -1 is
adjusted to M-1 when loaded into core and will not fold to R-1 and/or W-1
if R or W are not factors of M (M is size of core, R is the read limit, and
W is the write limit). Of course, if R = W = M, then play is equivalent
to ICWS'88 without limits.
In the 5.MARS section of the draft, many of the terms such as A-operand
were used both as containers ("Writes to the A-operand") and the contents
of those containers ("Compare the A-operand to ..."). Such ambiguous terms
and references have hopefully been eradicated.
Although such eradication eliminates ambiguity, it encourages obfuscation
and/or the proliferation of terms. A delicate balance has, perhaps, been
struck between the two.
The following are terms which are new or may be used differently than in
the past. All terms are contents (not containers).
opcode modifier : Removes mode-specific behaviour from opcodes by
explicitly stating whether an instruction uses just one number,
two numbers, or a whole instruction.
A-number : Replaces A-field/A-value/A-term, etc. A general term, not tied
to any specific instruction.
B-number : Replaces B-field/B-value/B-term, etc. A general term, not tied
to any specific instruction.
current instruction : Specifically means the instruction in the instruction
register. Does NOT mean the instruction in core pointed to by the
program counter. (That instruction may have changed since the
current instruction was copied from there).
A-instruction : Specifically means the copy of the instruction in core (at
the time of A-operand evaluation) pointed to by the A-number.
B-instruction : Specifically means the copy of the instruction in core (at
the time of B-operand evaluation) pointed to by the B-number.
A-value : Now refers to the object(s) (A/B-number(s) of the A-instruction
or the A-instruction) referenced by the A-operand (as selected by
the opcode modifier).
B-value : Now refers to the object(s) (A/B-number(s) of the B-instruction
or the B-instruction) referenced by the B-operand (as selected by
the opcode modifier).
B-target: The object(s) (A/B-number(s) of the instruction in core [at the
time of opcode execution] or the instruction) pointed to by the
B-number.
Six opcode modifiers have been added to the Draft. Modifiers are appended
to the opcodes with a dot. Example: "MOV.A". The modifiers are:
.A Instructions use and write A-numbers.
.B Instructions use and write B-numbers.
.AB Instructions use the A-numbers of the A-instructions and the
B-numbers of the B-instructions and write B-numbers.
.BA Instructions use the B-numbers of the A-instructions and the
A-numbers of the B-instructions and write A-numbers.
.F Instructions use both the A-numbers and the B-numbers, using and
writing A-to-A, B-to-B.
.X Instructions use both the A-numbers and the B-numbers, using and
writing A-to-B, B-to-A.
.I Instructions use and write entire instructions.
See Section 5.4 for more information (especially the examples).
There could be modifiers (other than .I) which take the modes into account,
but their utility may not warrant their inclusion.
The advantages of opcode modifiers include: greatly expanding the function
of opcodes without greatly expanding the number of opcodes, separating
opcode evaluation from operand evaluation (i.e. the behaviours of the
opcodes no longer depend on the modes), rendering moot questions about
whether ADD, SUB, etc. should use one or two fields (and if one field,
whether to use the A-field or the B-field), adding versatility to the order
of task splitting, and providing a "Skip if greater than" equivalent to
SLT.
In addition, backwards compatibility with ICWS'88 (and even ICWS'86) is
easily accomplished at the assembly level. Any instructions with opcodes
without modifiers would be translated to the appropriate opcode.modifier
pair. Examples:
"MOV #a, B", which only moves the A-field of the current instruction to the
B-field of the instruction pointed to by B, would be translated to
"MOV.AB #a, B". Similarly, "MOV a, b", which moves an entire instruction
from A to B, becomes "MOV.I a, b". Instructions which were previously
impossible, such as moving a B-field to an A-field, are now very
simple and intuitive with "MOV.BA A, B". Another example,
"MOV.X target, target" takes the place of "XCH target", exchanging fields.
Finally, "ADD a, b" would translate to "ADD.F a, b" for ICWS'88 and
"ADD.B a, b" for ICWS'86.
There is one negative to one opcode modifier. ".I" only really makes sense
for MOV and CMP. It would be possible to define results for arithmetic
manipulation and ordinal comparison of opcodes and modes, but it would be
very artificial. As an alternative, .I falls back to .F functionality (for
opcodes other than MOV and CMP) in this document.
Things which absolutely must be done before final consideration for
adoption by the ICWS:
1. Complete incomplete sections or remove references to them
2. Add typographic distinctions to grammars
To aid in completion of the draft, all suggested revisions of the draft
should consist of explicit remarks such as:
Delete lines xxxx to yyyy
Add the following after line zzzz ....
Replace lines vvvv to wwww with ....
Please individually explain why each revision is necessary.
The maximal verbosity of the draft is intentional. Each sentence either
presents a new item, a clarification of an item, or an old item in a new
context. The goal is that no two reasonable people could arrive at
two different interpretations of the draft.
\start numbering
0001 Draft of Proposed 1994 Core War Standard
0002 Version 3.3
0003 Draft Last Modified: November 8, 1995
0004 Last modified by: Damien Doligez
0005 Base draft by: Mark Durham
0006 i. Contents
0007 1. Introduction
0008 1. Purpose
0009 2. Overview
0010 3. Acknowledgements
0011 2. Redcode Assembly File Format
0012 1. Purpose
0013 2. Description
0014 3. Grammar
0015 4. Assembly To Object Code Conversion
0016 5. Pseudo-instructions
0017 6. Comment Conventions
0018 7. Example Assembly File
0019 3. Load File Format
0020 1. Purpose
0021 2. Description
0022 3. Grammar
0023 4. Comment Conventions
0024 5. Example Load File
0025 4. Run-time Variables
0026 1. Purpose
0027 2. Predefined Labels
0028 3. Variables
0029 4. Standard Variable Sets
0030 5. MARS
0031 1. Purpose
0032 2. Description
0033 3. Address Modes
0034 1. Immediate
0035 2. Direct
0036 3. A-number Indirect
0037 4. B-number Indirect
0038 5. A-number Predecrement Indirect
0039 6. B-number Predecrement Indirect
0040 7. A-number Postincrement Indirect
0041 8. B-number Postincrement Indirect
0042 4. Modifiers
0043 1. A
0044 2. B
0045 3. AB
0046 4. BA
0047 5. F
0048 6. X
0049 7. I
0050 5. Instruction Set
0051 1. DAT
0052 2. MOV
0053 3. ADD
0054 4. SUB
0055 5. MUL
0056 6. DIV
0057 7. MOD
0058 8. JMP
0059 9. JMZ
0060 10. JMN
0061 11. DJN
0062 12. SEQ and CMP
0063 13. SNE
0064 14. SLT
0065 15. SPL
0066 16. NOP
0067 6. Example MARS interpreter
0068 6. Validation Suite
0069 1. Purpose and Requirements
0070 2. Tests
0071 1. Assembly to Load File Test
0072 2. MARS Tests
0073 1. DAT Tests
0074 2. MOV Tests
0075 3. ADD Tests
0076 4. SUB Tests
0077 5. MUL Tests
0078 6. DIV Tests
0079 7. MOD Tests
0080 8. JMP Tests
0081 9. JMZ Tests
0082 10. JMN Tests
0083 11. DJN Tests
0084 12. SEQ/CMP Tests
0085 13. SNE Tests
0086 14. SLT Tests
0087 15. SPL Tests
0088 16. NOP Tests
0089 7. Glossary and Index
0090 A. Differences Between Standards
0091 1. Purpose
0092 2. Changes
0093 1. Assembly Files
0094 1. ICWS'88 conversion
0095 2. ICWS'86 conversion
0096 2. Load Files
0097 3. MARS
0098 1. Introduction
0099 1.1 Purpose
0100 This standard seeks to fully define and describe the game of Core War.
0101 1.2 Overview
0102 Core War is a game in which programs compete for control of a computer
0103 called MARS (for Memory Array Redcode Simulator). Redcode is the name
0104 of the assembly language in which Core War programs, called warriors,
0105 are written.
0106 In order to play Core Wars, access to a Core War system is required.
0107 A Core War system at a minimum must have a MARS executive function
0108 (interpreter) and a way to load warriors into core (the MARS memory).
0109 Most systems include a Redcode assembler, either separately or as part
0110 of the loader. Also, many systems include a graphical interface and
0111 code debugging features. Some systems have the ability to run
0112 automated tournaments.
0113 1.3 Acknowledgements
0114 This document is the fourth standard for Core War, the first three
0115 being "Core War Guidelines" (March 1984) by D. G. Jones and
0116 A. K. Dewdney, the International Core War Society standard of 1986 -
0117 "Core Wars" (May 1986), principally authored by Graeme McRae and the
0118 "Core Wars Standard of 1988" (Summer 1988), principally authored by
0119 Thomas Gettys. The latter two standards are often referred to as
0120 ICWS'86 and ICWS'88, respectively.
0121 People who contributed to this document (in alphabetical order):
0122 Scott W. Adkins
0123 Mark A. Durham
0124 Anders Ivner
0125 Morten Due Joergensen
0126 Paul Kline
0127 Scott Nelson
0128 Jon Newman
0129 John Perry
0130 Andy Pierce
0131 Planar
0132 Wayne Sheppard
0133 William Shubert
0134 Nandor Sieben
0135 Stefan Strack
0136 Mintardjo Wangsaw
0137 Kevin Whyte
0138 2. Redcode Assembly File Format
0139 2.1 Purpose
0140 A Redcode assembly file consists of the information necessary for a
0141 Redcode assembler to produce a load file. A standard assembly file
0142 format allows programmers to exchange warriors in a more meaningful
0143 format than load files. An assembly file, through the use of labels,
0144 arithmetic expressions, and macros can also greatly reduce the work
0145 necessary to produce a particular warrior while enhancing code
0146 readability.
0147 2.2 Description
0148 Each Redcode warrior consists of one or more lines of Redcode. Each
0149 line of Redcode consists of a string of alphanumerals and special
0150 characters. Special characters in Redcode are the addressing mode
0151 indicators for immediate '#', direct '$', A-number indirect '*',
0152 B-number indirect '@', A-number predecrement indirect '{', B-number
0153 predecrement indirect '<', A-number postincrement indirect '}', and
0154 B-number postincrement indirect '>' modes, the field separator
0155 (comma) ',', the comment indicator (semicolon) ';', the arithmetic
0156 operators for addition '+', subtraction '-', multiplication '*',
0157 division '/', and modulus '%', and opening '(' and closing ')'
0158 parentheses for precedence grouping.
0159 A line may be blank or consist of an instruction, a
0160 pseudo-instruction, a comment, or an instruction or
0161 pseudo-instruction followed by a comment. Each line is terminated
0162 with a newline. All comments begin with a semicolon. Each
0163 instruction consists of these elements in the following order: a
0164 label, an opcode, an A-operand, a comma, and a B-operand. Each
0165 element may be preceded and/or followed by whitespace (newline is
0166 not considered whitespace). The label is optional. If either
0167 operand is blank, the comma may be omitted. The operands may not
0168 be both blank.
0169 Pseudo-instructions appear just like instructions but are directives
0170 to the assembler and do not result in object code as an instruction
0171 would. Each pseudo-instruction has a pseudo-opcode which appears
0172 where an opcode would appear in an instruction. The format of the
0173 remainder of the pseudo-instruction depends on which pseudo-opcode is
0174 used. For the remainder of this section (2.2) and the next (2.3),
0175 references to "opcode" include "pseudo-opcode" assembler directives.
0176 A label is any alphanumeric string other than those reserved for
0177 opcodes. Labels are case sensitive, i.e. "start" is different from
0178 "Start". An opcode is any of the following: DAT, MOV, ADD, SUB, MUL,
0179 DIV, MOD, JMP, JMZ, JMN, DJN, CMP, SEQ, SNE, SLT, SPL, and NOP.
0180 Opcodes may be in upper or lower case or any combination. An opcode
0181 may be followed by a modifier. A modifier always begins with a dot.
0182 A modifier is any of the following: .A, .B, .AB, .BA, .F, .X, or .I.
0183 Modifiers may be in upper or lower case or any combination.
0184 Each operand is blank, contains an address, or contains an addressing
0185 mode indicator and an address. An address consists of any number of
0186 labels and numbers separated by arithmetic operators and possibly
0187 grouped with parentheses. All elements of an address may be separated
0188 by whitespace.
0189 2.3 Grammar
0190 Tokens are separated by whitespace (space and tab) exclusive of
0191 newline characters, which are used for line termination. End-of-file
0192 should occur only where newline could logically occur, otherwise the
0193 assembly file is invalid.
0194 In the following, 'e' is the "empty" element, meaning the token may be
0195 omitted, a caret '^' means NOT, an asterisk '*' immediately adjacent
0196 means zero or more occurrences of the previous token, and a plus '+'
0197 immediately adjacent means one or more occurrences of the previous
0198 token. The vertical bar '|' means OR.
0199 assembly_file:
0200 line+ EOF
0201 line:
0202 comment | instruction
0203 comment:
0204 ; v* newline | newline
0205 instruction:
0206 label_list operation mode expr comment |
0207 label_list operation mode expr , mode expr comment
0208 label_list:
0209 label newline* label_list | e
0210 label:
0211 alpha alphanumeral*
0212 operation:
0213 opcode | opcode.modifier
0214 opcode:
0215 DAT | MOV | ADD | SUB | MUL | DIV | MOD |
0216 JMP | JMZ | JMN | DJN | CMP | SEQ | SNE |
0217 SLT | SPL | NOP | ORG | EQU | END
0218 modifier:
0219 A | B | AB | BA | F | X | I
0220 mode:
0221 # | $ | * | @ | { | < | } | > | e
0222 expr:
0223 term |
0224 term + expr | term - expr |
0225 term * expr | term / expr |
0226 term % expr
0227 term:
0228 label | number | ( expression )
0229 number:
0230 whole_number | signed_integer
0231 signed_integer:
0232 +whole_number | -whole_number
0233 whole_number:
0234 numeral+
0235 alpha:
0236 A-Z | a-z | _
0237 numeral:
0238 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
0239 alphanumeral:
0240 alpha | numeral
0241 v:
0242 ^newline
0243 newline:
0244 LF | CR | LF CR | CR LF
0245 e:
0246 2.4 Assembly To Load File Conversion
0247 A Redcode program can be assembled into a list of MARS instructions.
0248 (When assembled to a file instead of directly to core, the list is
0249 called a load file. See Section 3). Each Redcode instruction
0250 assembles into a MARS instruction of five fields: an opcode.modifier
0251 field, the A-mode field, the A-address field, the B-mode field, and
0252 the B-address field. A missing (null or blank) mode assembles as '$'
0253 does.
0254 If no modifier is present in the assembly instruction, the appropriate
0255 modifier is appended to the opcode. The appropriate modifier depends
0256 upon the opcode, the modes, and which standard (ICWS'86 or ICWS'88) to
0257 consider (ICWS'88 by default). See Appendix A for the appropriate
0258 translations.
0259 The address field values are derived from the numbers, labels, and
0260 arithmetic operators contained in the addresses. Labels are
0261 converted to an address relative to the current instruction. Then
0262 the arithmetic operations are carried out according to the
0263 appropriate operator and parenthetical precedence to determine the
0264 final value. If there is only one operand associated with a DAT
0265 instruction, this operand is assembled into the B-mode and B-address
0266 fields, while #0 is assembled into the A-mode and A-address fields.
0267 For all other instructions with only one operand, this operand is
0268 assembled into the A-mode and A-address fields and #0 is assembled
0269 into the B-mode and B-address fields.
0270 2.5 Pseudo-instructions
0271 Pseudo-opcodes are "ORG", "EQU", and "END".
0272 "ORG" ("ORiGin") is a way for the assembly file to indicate the
0273 logical origin of the warrior. The A-operand contains an offset to
0274 the logical first instruction. Thus "ORG 0" means execution should
0275 start with the first instruction (the default) whereas "ORG 6" means
0276 execution should start with the seventh instruction. Although multiple
0277 ORG instructions are of no additional benefit to the programmer, they
0278 are allowed. When there is more than one ORG instruction in a file,
0279 the last ORG instruction encountered will be the one that takes
0280 effect.
0281 "EQU" ("EQUate") is a simple text substitution utility. Instructions
0282 of the form "label EQU text" will replace all occurrences of "label"
0283 with the (probably longer and more complicated) "text" before any
0284 actual assembly takes place on the file. Some labels are predefined
0285 with the value of run-time variables as if they were defined with
0286 EQU at the start of the program (see section 4.2 for the list of
0287 predefined labels).
0288 "END" indicates the logical end of the assembly file. If END has an
0289 A-operand, then the A-operand indicates the logical origin of the
0290 warrior in the same manner as ORG does. The rest of the file (after
0291 the end of the line containing END) is ignored.
0292 2.6 Comment Conventions
0293 ";redcode<switch>" as a first line identifies the file as a Redcode
0294 assembly file. The "<switch>" is optional and implementation
0295 dependent.
0296 ";strategy <text>" indicates a comment for "public" consumption.
0297 ";name <program name>", ";author <name of author(s)>",
0298 ";version <version number>", and ";date <date of last revision>"
0299 offer uniform ways of presenting this information.
0300 ";kill <program name>" is for removing warriors from ongoing
0301 tournaments. If no <program name> is supplied, all of the author's
0302 previous submissions will be removed.
0303 ";assert <expression>" will evaluate the expression and trigger
0304 an error if it is 0. In conjunction with predefined labels (see
0305 section 4.2), this provides a way of specifying the conditions under
0306 which a warrior is supposed to run.
0307 2.7 Example Assembly File
0308 ;redcode
0309 ;name Dwarf
0310 ;author A. K. Dewdney
0311 ;version 94.1
0312 ;date April 29, 1993
0313 ;strategy Bombs every fourth instruction.
0314 ;assert CORESIZE % 4 == 0
0315 ORG start ; Indicates the instruction with
0316 ; the label "start" should be the
0317 ; first to execute.
0318 step EQU 4 ; Replaces all occurrences of "step"
0319 ; with the character "4".
0320 target DAT.F #0, #0 ; Pointer to target instruction.
0321 start ADD.AB #step, target ; Increments pointer by step.
0322 MOV.AB #0, @target ; Bombs target instruction.
0323 JMP.A start ; Same as JMP.A -2. Loops back to
0324 ; the instruction labelled "start".
0325 END
0326 3. Load File Format
0327 3.1 Purpose
0328 A load file represents the minimum amount of information necessary for
0329 a warrior to execute properly and is presented in a very simple format
0330 which is a subset of the assembly file format presented in Section 2.
0331 A standard load file format allows programmers to choose assemblers
0332 and MARS programs separately and to verify assembler performance and
0333 MARS performance separately. Not all Core War systems will necessarily
0334 write load files (for example, those which assemble directly to core),
0335 but all systems should support reading load files.
0336 3.2 Description
0337 Each load file will consist of one or more lines of MARS
0338 instructions or comments. Each line is terminated with a newline.
0339 All comments start with with a semicolon. Each MARS instruction
0340 consists of five fields: an opcode.modifier pair, an A-mode, an
0341 A-field, a B-mode, and a B-field. The A-mode is separated from the
0342 opcode.modifier pair by whitespace and the B-mode is separated from
0343 the A-field by a comma and additional whitespace. Each MARS
0344 instruction may be followed by extraneous information, which is
0345 ignored. Note that the instruction format for load files is more
0346 rigid than for assembly files to simplify parsing. No blank modes or
0347 operands are allowed.
0348 3.3 Grammar
0349 Tokens are separated by whitespace (non-marking characters such as
0350 SPACE and TAB) exclusive of newline characters, which are used for
0351 line termination. End-of-file should occur only where newline could
0352 logically occur, otherwise the load file is invalid.
0353 load_file:
0354 line+ EOF
0355 line:
0356 comment | instruction
0357 comment:
0358 ; v* newline | newline
0359 instruction:
0360 opcode.modifier mode number , mode number comment
0361 opcode:
0362 DAT | MOV | ADD | SUB | MUL | DIV | MOD |
0363 JMP | JMZ | JMN | DJN | CMP | SEQ | SNE |
0364 SLT | SPL | NOP | ORG
0365 modifier:
0366 A | B | AB | BA | F | X | I
0367 mode:
0368 # | $ | @ | * | < | { | > | }
0369 number:
0370 whole_number | signed_integer
0371 signed_integer:
0372 +whole_number | -whole_number
0373 whole_number:
0374 numeral+
0375 numeral:
0376 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9
0377 v:
0378 ^newline
0379 newline:
0380 LF | CR | LF CR | CR LF
0381 3.4 Comment Conventions
0382 Comment conventions for load files are the same as for assembly files.
0383 Of particular note are the "; name <program name>" and "; author
0384 <author(s)>" comments. These comments provide a more suitable
0385 identification of programs to the MARS than "Warrior #1", "Warrior #2",
0386 etc. It also allows for less cryptic identification than by filename.
0387 3.5 Example Load File
0388 ;redcode
0389 ;name Dwarf
0390 ;author A. K. Dewdney
0391 ;version 94.1
0392 ;date April 29, 1993
0393 ;strategy Bombs every fourth instruction.
0394 ;assert CORESIZE % 4 == 0
0395 ORG 1 ; Indicates execution begins with the second
0396 ; instruction (ORG is not actually loaded, and is
0397 ; therefore not counted as an instruction).
0398 DAT.F #0, #0 ; Pointer to target instruction.
0399 ADD.AB #4, $-1 ; Increments pointer by step.
0400 MOV.AB #0, @-2 ; Bombs target instruction.
0401 JMP.A $-2, #0 ; Loops back two instructions.
0402 4. Run-time Variables
0403 4.1 Purpose
0404 This section describes those variables which are determined just prior
0405 to running a battle by the person running the battle. It also
0406 enumerates some of the standardized sets of variables used for
0407 tournaments.
0408 4.2 Predefined Labels
0409 Most of the run-time variables are available to the programmer as
0410 predefined labels. The purpose of these labels is twofold: first,
0411 to parameterize the warriors with the characteristics of their
0412 run-time environment; second, to check (with the ";assert" comment)
0413 that the warrior is run in an environment that makes sense for it.
0414 The next section gives a list of the run-time variables. When
0415 a predefined label takes the value of the variable, the label is
0416 given between parentheses after the name of the variable.
0417 4.2 Variables
0418 Run-time variables consist of the following:
0419 Core Size: (CORESIZE)
0420 Core size is the number of instructions which make up core
0421 during the battle.
0422 Cycles Before Tie: (MAXCYCLES)
0423 In each cycle, one instruction from each warrior is executed.
0424 This variable determines how many cycles without a winner
0425 should be executed before declaring a tie.
0426 Initial Instruction:
0427 The initial instruction is that instruction which is preloaded
0428 into core prior to loading warriors. In addition to loading
0429 an instruction such as "DAT #0, #0" into all of core, the
0430 initial instruction could be set to "NONE", meaning core should
0431 not be cleared between battles, or "RANDOM", meaning core
0432 instructions are filled with randomly generated instructions.
0433 Instruction Limit: (MAXLENGTH)
0434 The maximum number of instructions allowed per load file.
0435 Maximum Number of Tasks: (MAXPROCESSES)
0436 Each warrior can spawn multiple additional tasks. This
0437 variable sets the maximum number of tasks allowed per warrior.
0438 In other words, this is the size of each warrior's task queue.
0439 Minimum Separation: (MINDISTANCE)
0440 The minimum number of instructions from the first instruction
0441 of one warrior to the first instruction of the next warrior.
0442 Read Distance:
0443 This is the range available for warriors to read information
0444 from core. Attempts to read outside the limits of this range
0445 result in reading within the local readable range. The range
0446 is centered on the current instruction. Thus, a range of
0447 500 limits reading to offsets of (-249 -> +250) from the
0448 currently executing instruction. The read limit can therefore
0449 be considered a mini-core within core. An attempt to read
0450 location PC+251 reads location PC-249 instead. An attempt to
0451 read location PC+500 reads location PC instead.
0452 Read distance must be a factor of core size, otherwise the
0453 above defined behaviour is not guaranteed.
0454 Separation:
0455 The number of instructions from the first instruction of one
0456 warrior to the first instruction of the next warrior.
0457 Separation can be set to "RANDOM", meaning separations will be
0458 chosen randomly from those larger than the minimum separation.
0459 Warriors:
0460 The initial number of warriors to battle simultaneously in
0461 core.
0462 Write Distance:
0463 This is the range available for warriors to write information
0464 to core. Attempts to write outside the limits of this range
0465 result in writing within the local writable range. The range
0466 is centered on the current instruction. Thus, a range of 500
0467 limits writing to offsets of (-249 -> +250) from the
0468 currently executing instruction. The write limit can
0469 therefore be considered a mini-core within core. An attempt
0470 to write location PC+251 writes to location PC-249 instead.
0471 An attempt to write to location PC+500 writes to location PC
0472 instead.
0473 Write distance must be a factor of core size, otherwise the
0474 above defined behaviour is not guaranteed.
0475 4.3 Standard Variable Sets
0476 ICWS86:
0477 Core Size: 8192
0478 Cycles Before Tie: 100000
0479 Initial Instruction: DAT.F #0, #0
0480 Instruction Limit: 300
0481 Maximum Number of Tasks: 64
0482 Minimum Separation: 300
0483 Read Distance: 8192
0484 Separation: RANDOM
0485 Warriors: 2
0486 Write Distance: 8192
0487 KOTH:
0488 Core Size: 8000
0489 Cycles Before Tie: 80000
0490 Initial Instruction: DAT.F $0, $0
0491 Instruction Limit: 100
0492 Maximum Number of Tasks: 8000
0493 Minimum Separation: 100
0494 Read Distance: 8000
0495 Separation: RANDOM
0496 Warriors: 2
0497 Write Distance: 8000
0498 5. MARS
0499 5.1 Purpose
0500 The Memory Array Redcode Simulator (MARS) is the computer in which
0501 Core War warriors do combat.
0502 5.2 Description
0503 A minimally-complete MARS consists of a core, a loader, task queues,
0504 the MARS executive function, and a way to present the final results of
0505 a battle. Additionally, many MARS provide a "real-time" battle
0506 display and various debugging tools.
0507 The core consists of a cyclic list (0, 1, 2, ..., M-2, M-1, 0, 1, ...)
0508 of M MARS instructions. The integer M is referred to as "core size".
0509 All operations are performed modulo M. Core initialization (the
0510 initial instructions placed in core before loading warriors) is a
0511 run-time variable (see Section 4).
0512 The loader loads warriors into core, converting each negative field
0513 value N to the positive field value P such that 0 <= P < M and P = kM
0514 + N where k is a positive integer (P = N modulo M). Each field value
0515 G greater than or equal to M is converted to the field values L such
0516 that 0 <= L < M and L = kM + G where k is a negative integer (L = G
0517 modulo M). The loader also initializes each warrior's task queue with
0518 the appropriate task pointer.
0519 There is a task queue for each warrior loaded into core. Each task
0520 queue can hold a limited number of task pointers. The "task limit"
0521 (number of tasks an individual warrior's task queue can hold) is a
0522 run-time variable. The task queues are FIFOs (First In, First Out).
0523 Each warrior consists of one task initially. Subsequent tasks are
0524 added to the warrior's task queue using the SPL instruction. Attempted
0525 execution of a DAT instruction by a task effectively removes that task
0526 from the warrior's task queue.
0527 Warriors execute for a specified number of cycles ("time limit", see
0528 Section 4) or until only one warrior is still executing, whichever
0529 occurs first. Each cycle, one instruction from each warrior is
0530 executed. The instruction to execute is the instruction pointed to by
0531 the next task pointer in the warrior's task queue. A warrior is no
0532 longer executing when its task queue is empty.
0533 The following expressions are used in describing the MARS executive
0534 function's operation.
0535 General Definitions:
0536 An instruction consists of an opcode, a modifier, an A-operand,
0537 and a B-operand.
0538 An A-operand consists of an A-mode and an A-number.
0539 An A-mode is the addressing mode of an A-operand.
0540 An A-number is an integer between 0 and M-1, inclusive.
0541 A B-operand consists of a B-mode and a B-number.
0542 A B-mode is the addressing mode of a B-operand.
0543 A B-number is an integer between 0 and M-1, inclusive.
0544 Specific Definitions:
0545 The program counter (PC) is the pointer to the location in core of
0546 the instruction fetched from core to execute.
0547 The current instruction is the instruction in the instruction
0548 register, as copied (prior to execution) from the PC
0549 location of core.
0550 The A-pointer points to the instruction the A-operand of the
0551 current instruction references in core.
0552 The A-instruction is a copy of the instruction the A-pointer
0553 points to in core (as it was during operand evaluation).
0554 The A-value is the A-number and/or the B-number of the
0555 A-instruction or the A-instruction itself, whichever are/is
0556 selected by the opcode modifier.
0557 The B-pointer points to the instruction the B-operand of the
0558 current instruction references in core.
0559 The B-instruction is a copy of the instruction the B-pointer
0560 points to in core (as it was during operand evaluation).
0561 The B-value is the A-number and/or the B-number of the
0562 B-instruction or the B-instruction itself, whichever are/is
0563 selected by the opcode modifier.
0564 The B-target is the A-number and/or the B-number of the instruction
0565 pointed to by the B-pointer or the instruction itself,
0566 whichever are/is selected by the opcode modifier.
0567 All MARS instructions are executed following the same procedure:
0568 1. The currently executing warrior's current task pointer is
0569 extracted from the warrior's task queue and assigned to the
0570 program counter.
0571 2. The corresponding instruction is fetched from core and stored in
0572 the instruction register as the current instruction.
0573 3. The A-operand of the current instruction is evaluated.
0574 4. The results of A-operand evaluation, the A-pointer and the
0575 A-instruction, are stored in the appropriate registers.
0576 5. The B-operand of the current instruction is evaluated.
0577 6. The results of B-operand evaluation, the B-pointer and the
0578 B-instruction, are stored in the appropriate registers.
0579 7. Operations appropriate to the opcode.modifier pair in the
0580 instruction register are executed. With the exception of DAT
0581 instructions, all operations queue an updated task pointer.
0582 (How the task pointer is updated and when it is queued depend on
0583 instruction execution).
0584 All pointers are PC-relative, indicating the offset from the source of
0585 the current instruction to the desired location. All arithmetic is to
0586 be done modulo M, with negative values converted in the same manner as
0587 during loading as discussed above (P = M + N). Additionally, all
0588 reads of core are done modulo the read limit (R) and all writes of
0589 core are done modulo the write limit (W). Read offsets O greater than
0590 R/2 from the current instruction are converted to backwards offsets of
0591 O = O - R. A comparable conversion occurs for write offsets greater
0592 than W/2.
0593 5.3 Address Modes
0594 5.3.1 Immediate
0595 An immediate mode operand merely serves as storage for data. An
0596 immediate A/B-mode in the current instruction sets the A/B-pointer to
0597 zero.
0598 5.3.2 Direct
0599 A direct mode operand indicates the offset from the program counter.
0600 A direct A/B-mode in the current instruction means the A/B-pointer is
0601 a copy of the offset, the A/B-number of the current instruction.
0602 5.3.3 A-number Indirect
0603 An A-number indirect mode operand indicates the primary offset
0604 (relative to the program counter) to the secondary offset (relative to
0605 the location of the instruction in which the secondary offset is
0606 contained). An A-number indirect A/B-mode indicates that the
0607 A/B-pointer is the sum of the A/B-number of the current instruction
0608 (the primary offset) and the A-number of the instruction pointed to by
0609 the A/B-number of the current instruction (the secondary offset).
0610 5.3.4 B-number Indirect
0611 A B-number indirect mode operand indicates the primary offset
0612 (relative to the program counter) to the secondary offset (relative to
0613 the location of the instruction in which the secondary offset is
0614 contained). A B-number indirect A/B-mode indicates that the
0615 A/B-pointer is the sum of the A/B-number of the current instruction
0616 (the primary offset) and the B-number of the instruction pointed to by
0617 the A/B-number of the current instruction (the secondary offset).
0618 5.3.5 A-number Predecrement Indirect
0619 An A-number predecrement indirect mode operand indicates the primary
0620 offset (relative to the program counter) to the secondary offset
0621 (relative to the location of the instruction in which the secondary
0622 offset is contained) which is decremented prior to use. An A-number
0623 predecrement indirect A/B-mode indicates that the A/B-pointer is the
0624 sum of the A/B-number of the current instruction (the primary offset)
0625 and the decremented A-number of the instruction pointed to by the
0626 A/B-number of the current instruction (the secondary offset).
0627 5.3.6 B-number Predecrement Indirect
0628 A B-number predecrement indirect mode operand indicates the primary
0629 offset (relative to the program counter) to the secondary offset
0630 (relative to the location of the instruction in which the secondary
0631 offset is contained) which is decremented prior to use. A B-number
0632 predecrement indirect A/B-mode indicates that the A/B-pointer is the
0633 sum of the A/B-number of the current instruction (the primary offset)
0634 and the decremented B-number of the instruction pointed to by the
0635 A/B-number of the current instruction (the secondary offset).
0636 5.3.7 A-number Postincrement Indirect
0637 An A-number postincrement indirect mode operand indicates the primary
0638 offset (relative to the program counter) to the secondary offset
0639 (relative to the location of the instruction in which the secondary
0640 offset is contained) which is incremented after the results of the
0641 operand evaluation are stored. An A-number postincrement indirect
0642 A/B-mode indicates that the A/B-pointer is the sum of the A/B-number of
0643 the current instruction (the primary offset) and the A-number of the
0644 instruction pointed to by the A/B-number of the current instruction
0645 (the secondary offset). The A-number of the instruction pointed to by
0646 the A/B-number of the current instruction is incremented after the
0647 A/B-instruction is stored, but before the B-operand is evaluated (for
0648 A-number postincrement indirect A-mode), or the operation is executed
0649 (for A-number postincrement indirect B-mode).
0650 5.3.8 B-number Postincrement Indirect
0651 A B-number postincrement indirect mode operand indicates the primary
0652 offset (relative to the program counter) to the secondary offset
0653 (relative to the location of the instruction in which the secondary
0654 offset is contained) which is incremented after the results of the
0655 operand evaluation are stored. A B-number postincrement indirect
0656 A/B-mode indicates that the A/B-pointer is the sum of the A/B-number of
0657 the current instruction (the primary offset) and the B-number of the
0658 instruction pointed to by the A/B-number of the current instruction
0659 (the secondary offset). The B-number of the instruction pointed to by
0660 the A/B-number of the current instruction is incremented after the
0661 A/B-instruction is stored, but before the B-operand is evaluated (for
0662 B-number postincrement indirect A-mode), or the operation is executed
0663 (for B-number postincrement indirect B-mode).
0664 5.4 Modifiers
0665 5.4.1 A
0666 Instruction execution proceeds with the A-value set to the A-number of
0667 the A-instruction and the B-value set to the A-number of the
0668 B-instruction. A write to core replaces the A-number of the
0669 instruction pointed to by the B-pointer.
0670 For example, a CMP.A instruction would compare the A-number of the
0671 A-instruction with the A-number of the B-instruction. A MOV.A
0672 instruction would replace the A-number of the instruction pointed to
0673 by the B-pointer with the A-number of the A-instruction.
0674 5.4.2 B
0675 Instruction execution proceeds with the A-value set to the B-number of
0676 the A-instruction and the B-value set to the B-number of the
0677 B-instruction. A write to core replaces the B-number of the
0678 instruction pointed to by the B-pointer.
0679 For example, a CMP.B instruction would compare the B-number of the
0680 A-instruction with the B-number of the B-instruction. A MOV.B
0681 instruction would replace the B-number of the instruction pointed to
0682 by the B-pointer with the B-number of the A-instruction.
0683 5.4.3 AB
0684 Instruction execution proceeds with the A-value set to the A-number of
0685 the A-instruction and the B-value set to the B-number of the
0686 B-instruction. A write to core replaces the B-number of the
0687 instruction pointed to by the B-pointer.
0688 For example, a CMP.AB instruction would compare the A-number of the
0689 A-instruction with the B-number of the B-instruction. A MOV.AB
0690 instruction would replace the B-number of the instruction pointed to
0691 by the B-pointer with the A-number of the A-instruction.
0692 5.4.4 BA
0693 Instruction execution proceeds with the A-value set to the B-number of
0694 the A-instruction and the B-value set to the A-number of the
0695 B-instruction. A write to core replaces the A-number of the
0696 instruction pointed to by the B-pointer.
0697 For example, a CMP.BA instruction would compare the B-number of the
0698 A-instruction with the A-number of the B-instruction. A MOV.BA
0699 instruction would replace the A-number of the instruction pointed to
0700 by the B-pointer with the B-number of the A-instruction.
0701 5.4.5 F
0702 Instruction execution proceeds with the A-value set to both the
0703 A-number and B-number of the A-instruction (in that order) and the
0704 B-value set to both the A-number and B-number of the B-instruction
0705 (also in that order). A write to core replaces both the A-number and
0706 the B-number of the instruction pointed to by the B-pointer (in that
0707 order).
0708 For example, a CMP.F instruction would compare the A-number of the
0709 A-instruction to the A-number of the B-instruction and the B-number of
0710 the A-instruction to B-number of the B-instruction. A MOV.F
0711 instruction would replace the A-number of the instruction pointed to by
0712 the B-pointer with the A-number of the A-instruction and would also
0713 replace the B-number of the instruction pointed to by the B-pointer
0714 with the B-number of the A-instruction.
0715 5.4.6 X
0716 Instruction execution proceeds with the A-value set to both the
0717 A-number and B-number of the A-instruction (in that order) and the
0718 B-value set to both the B-number and A-number of the B-instruction
0719 (in that order). A write to to core replaces both the B-number and
0720 the A-number of the instruction pointed to by the B-pointer (in that
0721 order).
0722 For example, a CMP.X instruction would compare the A-number of the
0723 A-instruction to the B-number of the B-instruction and the B-number of the
0724 A-instruction to A-number of the B-instruction. A MOV.X instruction
0725 would replace the B-number of the instruction pointed to by the
0726 B-pointer with the A-number of the A-instruction and would also replace
0727 the A-number of the instruction pointed to by the B-pointer with the
0728 B-number of the A-instruction.
0729 5.4.7 I
0730 Instruction execution proceeds with the A-value set to the
0731 A-instruction and the B-value set to the B-instruction. A write to
0732 core replaces the entire instruction pointed to by the B-pointer.
0733 For example, a CMP.I instruction would compare the A-instruction to
0734 the B-instruction. A MOV.I instruction would replace the instruction
0735 pointed to by the B-pointer with the A-instruction.
0736 5.5 Instruction Set
0737 5.5.1 DAT
0738 No additional processing takes place. This effectively removes the
0739 current task from the current warrior's task queue.
0740 5.5.2 MOV
0741 Move replaces the B-target with the A-value and queues the next
0742 instruction (PC + 1).
0743 5.5.3 ADD
0744 ADD replaces the B-target with the sum of the A-value and the B-value
0745 (A-value + B-value) and queues the next instruction (PC + 1). ADD.I
0746 functions as ADD.F would.
0747 5.5.4 SUB
0748 SUB replaces the B-target with the difference of the B-value and the
0749 A-value (B-value - A-value) and queues the next instruction (PC + 1).
0750 SUB.I functions as SUB.F would.
0751 5.5.5 MUL
0752 MUL replaces the B-target with the product of the A-value and the
0753 B-value (A-value * B-value) and queues the next instruction (PC + 1).
0754 MUL.I functions as MUL.F would.
0755 5.5.6 DIV
0756 DIV replaces the B-target with the integral result of dividing the
0757 B-value by the A-value (B-value / A-value) and queues the next
0758 instruction (PC + 1). DIV.I functions as DIV.F would. If the
0759 A-value is zero, the B-value is unchanged and the current task is
0760 removed from the warrior's task queue. DIV.I, DIV.F, and DIV.X
0761 operate on pairs of operands. If either component of the A-value
0762 is zero, the corresponding component of the B-value is unchanged
0763 (the other component is divided normally), and the current task is
0764 removed from the warrior queue.
0765 5.5.7 MOD
0766 MOD replaces the B-target with the integral remainder of dividing the
0767 B-value by the A-value (B-value % A-value) and queues the next
0768 instruction (PC + 1). MOD.I functions as MOD.F would. If the
0769 A-value is zero, the B-value is unchanged and the current task is
0770 removed from the warrior's task queue. MOD.I, MOD.F, and MOD.X
0771 operate on pairs of operands. If either component of the A-value
0772 is zero, the corresponding component of the B-value is unchanged
0773 (the other component is divided normally), and the current task is
0774 removed from the warrior queue.
0775 5.5.8 JMP
0776 JMP queues the sum of the program counter and the A-pointer.
0777 5.5.9 JMZ
0778 JMZ tests the B-value to determine if it is zero. If the B-value is
0779 zero, the sum of the program counter and the A-pointer is queued.
0780 Otherwise, the next instruction is queued (PC + 1). JMZ.I functions
0781 as JMZ.F would, i.e. it jumps if both the A-number and the B-number
0782 of the B-instruction are zero.
0783 5.5.10 JMN
0784 JMN tests the B-value to determine if it is zero. If the B-value is
0785 not zero, the sum of the program counter and the A-pointer is queued.
0786 Otherwise, the next instruction is queued (PC + 1). JMN.I functions
0787 as JMN.F would, i.e. it jumps if the A-number or the B-number of the
0788 B-instruction (or both) is non-zero. This is the negation of the
0789 condition for JMZ.F.
0790 5.5.11 DJN
0791 DJN decrements the B-value and the B-target, then tests the B-value
0792 to determine if it is zero. If the decremented B-value is not zero,
0793 the sum of the program counter and the A-pointer is queued.
0794 Otherwise, the next instruction is queued (PC + 1). DJN.I functions
0795 as DJN.F would, i.e. it decrements both both A/B-numbers of the B-value
0796 and the B-target, and jumps if one (or both) of the A/B-numbers of the
0797 B-value is non-zero.
0798 5.5.12 SEQ and CMP
0799 SEQ and CMP are synonymous opcodes. SEQ is provided as an
0800 easy-to-remember mnemonic, and CMP is provided for backward
0801 compatibility. They are completely equivalent. SEQ (or CMP) compares
0802 the A-value to the B-value. If the result of the comparison is equal,
0803 the instruction after the next instruction (PC + 2) is queued (skipping
0804 the next instruction). Otherwise, the next instruction is queued
0805 (PC + 1).
0806 5.5.13 SNE
0807 SNE compares the A-value to the B-value. If the result of the
0808 comparison is not equal, the instruction after the next instruction
0809 (PC + 2) is queued (skipping the next instruction). Otherwise, the
0810 next instruction is queued (PC + 1).
0811 5.5.14 SLT
0812 SLT compares the A-value to the B-value. If the A-value is less than
0813 the B-value, the instruction after the next instruction (PC + 2) is
0814 queued (skipping the next instruction). Otherwise, the next
0815 instruction is queued (PC + 1). SLT.I functions as SLT.F would, i.e.
0816 the next instruction is skipped only if each of the A/B-numbers of the
0817 A-value is less than its B-value counterpart.
0818 5.5.15 SPL
0819 SPL queues the next instruction (PC + 1) and then queues the sum of
0820 the program counter and the A-pointer. If the queue is full, only the
0821 next instruction is queued.
0822 5.5.16 NOP
0823 NOP queues the next instruction (PC + 1).
0824 5.6 Example MARS Interpreter
0825 /************************************/
0826 /* */
0827 /* EMI94.c */
0828 /* */
0829 /* Execute MARS Instruction ala */
0830 /* ICWS'94 Draft Standard. */
0831 /* */
0832 /* Last Update: November 8, 1995 */
0833 /* */
0834 /************************************/
0835 /* This ANSI C function is the benchmark MARS instruction */
0836 /* interpreter for the ICWS'94 Draft Standard. */
0837 /* The design philosophy of this function is to mirror the */
0838 /* standard as closely as possible, illuminate the meaning */
0839 /* of the standard, and provide the definitive answers to */
0840 /* questions of the "well, does the standard mean this or */
0841 /* that?" variety. Although other, different implemen- */
0842 /* tations are definitely possible and encouraged; those */
0843 /* implementations should produce the same results as this */
0844 /* one does. */
0845 /* The function returns the state of the system. What the */
0846 /* main program does with this information is not defined */
0847 /* by the standard. */
0848 enum SystemState {
0849 UNDEFINED,
0850 SUCCESS
0851 };
0852 /* Any number of warriors may be executing in core at one */
0853 /* time, depending on the run-time variable set and how */
0854 /* many warriors have failed during execution. For this */
0855 /* implementation, warriors are identified by the order in */
0856 /* which they were loaded into core. */
0857 typedef unsigned int Warrior;
0858 /* An Address in Core War can be any number from 0 to the */
0859 /* size of core minus one, relative to the current */
0860 /* instruction. In this implementation, core is an array */
0861 /* of instructions; therefore any variable types which */
0862 /* contain an Address can be considered to be of type */
0863 /* unsigned int. One caveat: for the purposes of this */
0864 /* standard, unsigned int must be considered to have no */
0865 /* upper limit. Depending on the size of core, it may be */
0866 /* necessary to take precautions against overflow. */
0867 typedef unsigned int Address;
0868 /* The FIFO task queues and supporting functions are not */
0869 /* presented. The function Queue() attempts to add a task */
0870 /* pointer to the back of the currently executing warrior's */
0871 /* task queue. No special actions are to be taken if */
0872 /* Queue() is unsuccessful, which it will be if the warrior */
0873 /* has already reached the task limit (maximum allowable */
0874 /* number of tasks). */
0875 extern void Queue(
0876 Warrior W,
0877 Address TaskPointer
0878 );
0879 /* There is one support function used to limit the range of */
0880 /* reading from Core and writing to Core relative to the */
0881 /* current instruction. Behaviour is as expected (a small */
0882 /* core within Core) only if the limits are factors of the */
0883 /* size of Core. */
0884 static Address Fold(
0885 Address pointer, /* The pointer to fold into the desired range. */
0886 Address limit, /* The range limit. */
0887 Address M /* The size of Core. */
0888 ) {
0889 Address result;
0890 result = pointer % limit;
0891 if ( result > (limit/2) ) {
0892 result += M - limit;
0893 };
0894 return(result);
0895 }
0896 /* Instructions are the principle data type. Core is an */
0897 /* array of instructions, and there are three instruction */
0898 /* registers used by the MARS executive. */
0899 enum Opcode {
0900 DAT,
0901 MOV,
0902 ADD,
0903 SUB,
0904 MUL,
0905 DIV,
0906 MOD,
0907 JMP,
0908 JMZ,
0909 JMN,
0910 DJN,
0911 CMP, /* aka SEQ */
0912 SNE,
0913 SLT,
0914 SPL,
0915 NOP,
0916 };
0917 enum Modifier {
0918 A,
0919 B,
0920 AB,
0921 BA,
0922 F,
0923 X,
0924 I
0925 };
0926 enum Mode {
0927 IMMEDIATE,
0928 DIRECT,
0929 A_INDIRECT,
0930 B_INDIRECT,
0931 A_DECREMENT,
0932 B_DECREMENT,
0933 A_INCREMENT,
0934 B_INCREMENT,
0935 };
0936 typedef struct Instruction {
0937 enum Opcode Opcode;
0938 enum Modifier Modifier;
0939 enum Mode AMode;
0940 Address ANumber;
0941 enum Mode BMode;
0942 Address BNumber;
0943 } Instruction;
0944 /* The function is passed which warrior is currently */
0945 /* executing, the address of the warrior's current task's */
0946 /* current instruction, a pointer to the Core, the size of */
0947 /* the Core, and the read and write limits. It returns the */
0948 /* system's state after attempting instruction execution. */
0949 enum SystemState EMI94(
0950 /* W indicates which warrior's code is executing. */
0951 Warrior W,
0952 /* PC is the address of this warrior's current task's */
0953 /* current instruction. */
0954 Address PC,
0955 /* Core is just an array of Instructions. Core has been */
0956 /* initialized and the warriors have been loaded before */
0957 /* calling this function. */
0958 Instruction Core[],
0959 /* M is the size of Core. */
0960 Address M,
0961 /* ReadLimit is the limitation on read distances. */
0962 Address ReadLimit,
0963 /* WriteLimit is the limitation on write distances. */
0964 Address WriteLimit
0965 ) {
0966 /* This MARS stores the currently executing instruction in */
0967 /* the instruction register IR. */
0968 Instruction IR;
0969 /* This MARS stores the instruction referenced by the */
0970 /* A-operand in the instruction register IRA. */
0971 Instruction IRA;
0972 /* This MARS stores the instruction referenced by the */
0973 /* B-operand in the instruction Register IRB. */
0974 Instruction IRB;
0975 /* All four of the following pointers are PC-relative */
0976 /* (relative to the Program Counter). Actual access of */
0977 /* core must add-in the Program Counter (mod core size). */
0978 /* The offset to the instruction referred to by the */
0979 /* A-operand for reading is Read Pointer A (RPA). */
0980 Address RPA;
0981 /* The offset to the instruction referred to by the */
0982 /* A-operand for writing is Write Pointer A (WPA). */
0983 Address WPA;
0984 /* The offset to the instruction referred to by the */
0985 /* B-operand for reading is Read Pointer B (RPB). */
0986 Address RPB;
0987 /* The offset to the instruction referred to by the */
0988 /* A-operand for writing is Write Pointer B (WPB). */
0989 Address WPB;
0990 /* Post-increment operands need to keep track of which */
0991 /* instruction to increment. */
0992 Address PIP;
0993 /* Before execution begins, the current instruction is */
0994 /* copied into the Instruction Register. */
0995 IR = Core[PC];
0996 /* Next, the A-operand is completely evaluated. */
0997 /* For instructions with an Immediate A-mode, the Pointer A */
0998 /* points to the source of the current instruction. */
0999 if (IR.AMode == IMMEDIATE) {
1000 RPA = WPA = 0;
1001 } else {
1002 /* For instructions with a Direct A-mode, the Pointer A */
1003 /* points to the instruction IR.ANumber away, relative to */
1004 /* the Program Counter. */
1005 /* Note that implementing Core as an array necessitates */
1006 /* doing all Address arithmetic modulus the size of Core. */
1007 RPA = Fold(IR.ANumber, ReadLimit, M);
1008 WPA = Fold(IR.ANumber, WriteLimit, M);
1009 /* For instructions with A-indirection in the A-operand */
1010 /* (A-number Indirect, A-number Predecrement, */
1011 /* and A-number Postincrement A-modes): */
1012 if (IR.AMode == A_INDIRECT
1013 || IR.AMode == A_DECREMENT
1014 || IR.AMode == A_INCREMENT) {
1015 /* For instructions with Predecrement A-mode, the A-Field */
1016 /* of the instruction in Core currently pointed to by the */
1017 /* Pointer A is decremented (M - 1 is added). */
1018 if (IR.AMode == A_DECREMENT) {
1019 Core[((PC + WPA) % M)].ANumber =
1020 (Core[((PC + WPA) % M)].ANumber + M - 1) % M;
1021 };
1022 /* For instructions with Postincrement A-mode, the A-Field */
1023 /* of the instruction in Core currently pointed to by the */
1024 /* Pointer A will be incremented. */
1025 if (IR.AMode == A_INCREMENT) {
1026 PIP = (PC + WPA) % M;
1027 };
1028 /* For instructions with A-indirection in the A-operand, */
1029 /* Pointer A ultimately points to the instruction */
1030 /* Core[((PC + PCA) % M)].ANumber away, relative to the */
1031 /* instruction pointed to by Pointer A. */
1032 RPA = Fold(
1033 (RPA + Core[((PC + RPA) % M)].ANumber), ReadLimit, M
1034 );
1035 WPA = Fold(
1036 (WPA + Core[((PC + WPA) % M)].ANumber), WriteLimit, M
1037 );
1038 };
1039 /* For instructions with B-indirection in the A-operand */
1040 /* (B-number Indirect, B-number Predecrement, */
1041 /* and B-number Postincrement A-modes): */
1042 if (IR.AMode == B_INDIRECT
1043 || IR.AMode == B_DECREMENT
1044 || IR.AMode == B_INCREMENT) {
1045 /* For instructions with Predecrement A-mode, the B-Field */
1046 /* of the instruction in Core currently pointed to by the */
1047 /* Pointer A is decremented (M - 1 is added). */
1048 if (IR.AMode == DECREMENT) {
1049 Core[((PC + WPA) % M)].BNumber =
1050 (Core[((PC + WPA) % M)].BNumber + M - 1) % M;
1051 };
1052 /* For instructions with Postincrement A-mode, the B-Field */
1053 /* of the instruction in Core currently pointed to by the */
1054 /* Pointer A will be incremented. */
1055 if (IR.AMode == INCREMENT) {
1056 PIP = (PC + WPA) % M;
1057 };
1058 /* For instructions with B-indirection in the A-operand, */
1059 /* Pointer A ultimately points to the instruction */
1060 /* Core[((PC + PCA) % M)].BNumber away, relative to the */
1061 /* instruction pointed to by Pointer A. */
1062 RPA = Fold(
1063 (RPA + Core[((PC + RPA) % M)].BNumber), ReadLimit, M
1064 );
1065 WPA = Fold(
1066 (WPA + Core[((PC + WPA) % M)].BNumber), WriteLimit, M
1067 );
1068 };
1069 };
1070 /* The Instruction Register A is a copy of the instruction */
1071 /* pointed to by Pointer A. */
1072 IRA = Core[((PC + RPA) % M)];
1073 /* If the A-mode was post-increment, now is the time to */
1074 /* increment the instruction in core. */
1075 if (IR.AMode == A_INCREMENT) {
1076 Core[PIP].ANumber = (Core[PIP].ANumber + 1) % M;
1077 }
1078 else if (IR.AMode == B_INCREMENT) {
1079 Core[PIP].BNumber = (Core[PIP].BNumber + 1) % M;
1080 };
1081 /* The Pointer B and the Instruction Register B are */
1082 /* evaluated in the same manner as their A counterparts. */
1083 if (IR.BMode == IMMEDIATE) {
1084 RPB = WPB = 0;
1085 } else {
1086 RPB = Fold(IR.BNumber, ReadLimit, M);
1087 WPB = Fold(IR.BNumber, WriteLimit, M);
1088 if (IR.BMode == A_INDIRECT
1089 || IR.BMode == A_DECREMENT
1090 || IR.BMode == A_INCREMENT) {
1091 if (IR.BMode == A_DECREMENT) {
1092 Core[((PC + WPB) % M)].ANumber =
1093 (Core[((PC + WPB) % M)].ANumber + M - 1) % M
1094 ;
1095 } else if (IR.BMode == A_INCREMENT) {
1096 PIP = (PC + WPB) % M;
1097 };
1098 RPB = Fold(
1099 (RPB + Core[((PC + RPB) % M)].ANumber), ReadLimit, M
1100 );
1101 WPB = Fold(
1102 (WPB + Core[((PC + WPB) % M)].ANumber), WriteLimit, M
1103 );
1104 };
1105 if (IR.BMode == B_INDIRECT
1106 || IR.BMode == B_DECREMENT
1107 || IR.BMode == B_INCREMENT) {
1108 if (IR.BMode == B_DECREMENT) {
1109 Core[((PC + WPB) % M)].BNumber =
1110 (Core[((PC + WPB) % M)].BNumber + M - 1) % M
1111 ;
1112 } else if (IR.BMode == B_INCREMENT) {
1113 PIP = (PC + WPB) % M;
1114 };
1115 RPB = Fold(
1116 (RPB + Core[((PC + RPB) % M)].BNumber), ReadLimit, M
1117 );
1118 WPB = Fold(
1119 (WPB + Core[((PC + WPB) % M)].BNumber), WriteLimit, M
1120 );
1121 };
1122 };
1123 IRB = Core[((PC + RPB) % M)];
1124 if (IR.BMode == A_INCREMENT) {
1125 Core[PIP].ANumber = (Core[PIP].ANumber + 1) % M;
1126 }
1127 else if (IR.BMode == INCREMENT) {
1128 Core[PIP].BNumber = (Core[PIP].BNumber + 1) % M;
1129 };
1130 /* Execution of the instruction can now proceed. */
1131 switch (IR.Opcode) {
1132 /* Instructions with a DAT opcode have no further function. */
1133 /* The current task's Program Counter is not updated and is */
1134 /* not returned to the task queue, effectively removing the */
1135 /* task. */
1136 case DAT: noqueue:
1137 break;
1138 /* MOV replaces the B-target with the A-value and queues */
1139 /* the next instruction. */
1140 case MOV:
1141 switch (IR.Modifier) {
1142 /* Replaces A-number with A-number. */
1143 case A:
1144 Core[((PC + WPB) % M)].ANumber = IRA.ANumber;
1145 break;
1146 /* Replaces B-number with B-number. */
1147 case B:
1148 Core[((PC + WPB) % M)].BNumber = IRA.BNumber;
1149 break;
1150 /* Replaces B-number with A-number. */
1151 case AB:
1152 Core[((PC + WPB) % M)].BNumber = IRA.ANumber;
1153 break;
1154 /* Replaces A-number with B-number. */
1155 case BA:
1156 Core[((PC + WPB) % M)].ANumber = IRA.BNumber;
1157 break;
1158 /* Replaces A-number with A-number and B-number with */
1159 /* B-number. */
1160 case F:
1161 Core[((PC + WPB) % M)].ANumber = IRA.ANumber;
1162 Core[((PC + WPB) % M)].BNumber = IRA.BNumber;
1163 break;
1164 /* Replaces B-number with A-number and A-number with */
1165 /* B-number. */
1166 case X:
1167 Core[((PC + WPB) % M)].BNumber = IRA.ANumber;
1168 Core[((PC + WPB) % M)].ANumber = IRA.BNumber;
1169 break;
1170 /* Copies entire instruction. */
1171 case I:
1172 Core[((PC + WPB) % M)] = IRA;
1173 break;
1174 default:
1175 return(UNDEFINED);
1176 break;
1177 };
1178 /* Queue up next instruction. */
1179 Queue(W, ((PC + 1) % M));
1180 break;
1181 /* Arithmetic instructions replace the B-target with the */
1182 /* "op" of the A-value and B-value, and queue the next */
1183 /* instruction. "op" can be the sum, the difference, or */
1184 /* the product. */
1185 #define ARITH(op) \
1186 switch (IR.Modifier) { \
1187 case A: \
1188 Core[((PC + WPB) % M)].ANumber = \
1189 (IRB.ANumber op IRA.ANumber) % M \
1190 ; \
1191 break; \
1192 case B: \
1193 Core[((PC + WPB) % M)].BNumber = \
1194 (IRB.BNumber op IRA.BNumber) % M \
1195 ; \
1196 break; \
1197 case AB: \
1198 Core[((PC + WPB) % M)].BNumber = \
1199 (IRB.ANumber op IRA.BNumber) % M \
1200 ; \
1201 break; \
1202 case BA: \
1203 Core[((PC + WPB) % M)].ANumber = \
1204 (IRB.BNumber op IRA.ANumber) % M \
1205 ; \
1206 break; \
1207 case F: \
1208 case I: \
1209 Core[((PC + WPB) % M)].ANumber = \
1210 (IRB.ANumber op IRA.ANumber) % M \
1211 ; \
1212 Core[((PC + WPB) % M)].BNumber = \
1213 (IRB.BNumber op IRA.BNumber) % M \
1214 ; \
1215 break; \
1216 case X: \
1217 Core[((PC + WPB) % M)].BNumber = \
1218 (IRB.ANumber op IRA.BNumber) % M \
1219 ; \
1220 Core[((PC + WPB) % M)].ANumber = \
1221 (IRB.BNumber op IRA.ANumber) % M \
1222 ; \
1223 break; \
1224 default: \
1225 return(UNDEFINED); \
1226 break; \
1227 }; \
1228 Queue(W, ((PC + 1) % M)); \
1229 break;
1230 case ADD: ARITH(+)
1231 case SUB: ARITH(+ M -)
1232 case MUL: ARITH(*)
1233 /* DIV and MOD replace the B-target with the integral */
1234 /* quotient (for DIV) or remainder (for MOD) of the B-value */
1235 /* by the A-value, and queues the next instruction. */
1236 /* Process is removed from task queue if A-value is zero. */
1237 #define ARITH_DIV(op) \
1238 switch (IR.Modifier) { \
1239 case A: \
1240 if (IRA.ANumber != 0) \
1241 Core[((PC + WPB) % M)].ANumber = IRB.ANumber op IRA.ANumber; \
1242 break; \
1243 case B: \
1244 if (IRA.BNumber != 0) \
1245 Core[((PC + WPB) % M)].BNumber = IRB.BNumber op IRA.BNumber; \
1246 else goto noqueue; \
1247 break; \
1248 case AB: \
1249 if (IRA.ANumber != 0) \
1250 Core[((PC + WPB) % M)].BNumber = IRB.BNumber op IRA.ANumber; \
1251 else goto noqueue; \
1252 break; \
1253 case BA: \
1254 if (IRA.BNumber != 0) \
1255 Core[((PC + WPB) % M)].ANumber = IRB.ANumber op IRA.BNumber; \
1256 else goto noqueue; \
1257 break; \
1258 case F: \
1259 case I: \
1260 if (IRA.ANumber != 0) \
1261 Core[((PC + WPB) % M)].ANumber = IRB.ANumber op IRA.ANumber; \
1262 if (IRA.BNumber != 0) \
1263 Core[((PC + WPB) % M)].BNumber = IRB.BNumber op IRA.BNumber; \
1264 if ((IRA.ANumber == 0) || (IRA.BNumber == 0)) \
1265 goto noqueue; \
1266 break; \
1267 case X: \
1268 if (IRA.ANumber != 0) \
1269 Core[((PC + WPB) % M)].BNumber = IRB.BNumber op IRA.ANumber; \
1270 if (IRA.BNumber != 0) \
1271 Core[((PC + WPB) % M)].ANumber = IRB.ANumber op IRA.BNumber; \
1272 if ((IRA.ANumber == 0) || (IRA.BNumber == 0)) \
1273 goto noqueue; \
1274 break; \
1275 default: \
1276 return(UNDEFINED); \
1277 break; \
1278 }; \
1279 Queue(W, ((PC + 1) % M)); \
1280 break;
1281 case DIV: ARITH_DIV(/)
1282 case MOD: ARITH_DIV(%)
1283 /* JMP queues the sum of the Program Counter and the */
1284 /* A-pointer. */
1285 case JMP:
1286 Queue(W, RPA);
1287 break;
1288 /* JMZ queues the sum of the Program Counter and Pointer A */
1289 /* if the B-value is zero. Otherwise, it queues the next */
1290 /* instruction. */
1291 case JMZ:
1292 switch (IR.Modifier) {
1293 case A:
1294 case BA:
1295 if (IRB.ANumber == 0) {
1296 Queue(W, RPA);
1297 } else {
1298 Queue(W, ((PC + 1) % M));
1299 };
1300 break;
1301 case B:
1302 case AB:
1303 if (IRB.BNumber == 0) {
1304 Queue(W, RPA);
1305 } else {
1306 Queue(W, ((PC + 1) % M));
1307 };
1308 break;
1309 case F:
1310 case X:
1311 case I:
1312 if ( (IRB.ANumber == 0) && (IRB.BNumber == 0) ) {
1313 Queue(W, RPA);
1314 } else {
1315 Queue(W, ((PC + 1) % M));
1316 };
1317 break;
1318 default:
1319 return(UNDEFINED);
1320 break;
1321 };
1322 break;
1323 /* JMN queues the sum of the Program Counter and Pointer A */
1324 /* if the B-value is not zero. Otherwise, it queues the */
1325 /* next instruction. */
1326 case JMN:
1327 switch (IR.Modifier) {
1328 case A:
1329 case BA:
1330 if (IRB.ANumber != 0) {
1331 Queue(W, RPA);
1332 } else {
1333 Queue(W, ((PC + 1) % M));
1334 };
1335 break;
1336 case B:
1337 case AB:
1338 if (IRB.BNumber != 0) {
1339 Queue(W, RPA);
1340 } else {
1341 Queue(W, ((PC + 1) % M));
1342 };
1343 break;
1344 case F:
1345 case X:
1346 case I:
1347 if ( (IRB.ANumber != 0) || (IRB.BNumber != 0) ) {
1348 Queue(W, RPA);
1349 } else {
1350 Queue(W, ((PC + 1) % M));
1351 };
1352 break;
1353 default:
1354 return(UNDEFINED);
1355 break;
1356 };
1357 break;
1358 /* DJN (Decrement Jump if Not zero) decrements the B-value */
1359 /* and the B-target, then tests if the B-value is zero. If */
1360 /* the result is not zero, the sum of the Program Counter */
1361 /* and Pointer A is queued. Otherwise, the next */
1362 /* instruction is queued. */
1363 case DJN:
1364 switch (IR.Modifier) {
1365 case A:
1366 case BA:
1367 Core[((PC + WPB) % M)].ANumber =
1368 (Core[((PC + WPB) % M)].ANumber + M - 1) % M
1369 ;
1370 IRB.ANumber -= 1;
1371 if (IRB.ANumber != 0) {
1372 Queue(W, RPA);
1373 } else {
1374 Queue(W, ((PC + 1) % M));
1375 };
1376 break;
1377 case B:
1378 case AB:
1379 Core[((PC + WPB) % M)].BNumber =
1380 (Core[((PC + WPB) % M)].BNumber + M - 1) % M
1381 ;
1382 IRB.BNumber -= 1;
1383 if (IRB.BNumber != 0) {
1384 Queue(W, RPA);
1385 } else {
1386 Queue(W, ((PC + 1) % M));
1387 };
1388 break;
1389 case F:
1390 case X:
1391 case I:
1392 Core[((PC + WPB) % M)].ANumber =
1393 (Core[((PC + WPB) % M)].ANumber + M - 1) % M
1394 ;
1395 IRB.ANumber -= 1;
1396 Core[((PC + WPB) % M)].BNumber =
1397 (Core[((PC + WPB) % M)].BNumber + M - 1) % M
1398 ;
1399 IRB.BNumber -= 1;
1400 if ( (IRB.ANumber != 0) || (IRB.BNumber != 0) ) {
1401 Queue(W, RPA);
1402 } else {
1403 Queue(W, ((PC + 1) % M));
1404 };
1405 break;
1406 default:
1407 return(UNDEFINED);
1408 break;
1409 };
1410 break;
1411 /* SEQ/CMP compares the A-value and the B-value. If there */
1412 /* are no differences, then the instruction after the next */
1413 /* instruction is queued. Otherwise, the next instrution */
1414 /* is queued. */
1415 case CMP:
1416 switch (IR.Modifier) {
1417 case A:
1418 if (IRA.ANumber == IRB.ANumber) {
1419 Queue(W, ((PC + 2) % M));
1420 } else {
1421 Queue(W, ((PC + 1) % M));
1422 };
1423 break;
1424 case B:
1425 if (IRA.BNumber == IRB.BNumber) {
1426 Queue(W, ((PC + 2) % M));
1427 } else {
1428 Queue(W, ((PC + 1) % M));
1429 };
1430 break;
1431 case AB:
1432 if (IRA.ANumber == IRB.BNumber) {
1433 Queue(W, ((PC + 2) % M));
1434 } else {
1435 Queue(W, ((PC + 1) % M));
1436 };
1437 break;
1438 case BA:
1439 if (IRA.BNumber == IRB.ANumber) {
1440 Queue(W, ((PC + 2) % M));
1441 } else {
1442 Queue(W, ((PC + 1) % M));
1443 };
1444 break;
1445 case F:
1446 if ( (IRA.ANumber == IRB.ANumber) &&
1447 (IRA.BNumber == IRB.BNumber)
1448 ) {
1449 Queue(W, ((PC + 2) % M));
1450 } else {
1451 Queue(W, ((PC + 1) % M));
1452 };
1453 break;
1454 case X:
1455 if ( (IRA.ANumber == IRB.BNumber) &&
1456 (IRA.BNumber == IRB.ANumber)
1457 ) {
1458 Queue(W, ((PC + 2) % M));
1459 } else {
1460 Queue(W, ((PC + 1) % M));
1461 };
1462 break;
1463 case I:
1464 if ( (IRA.Opcode == IRB.Opcode) &&
1465 (IRA.Modifier == IRB.Modifier) &&
1466 (IRA.AMode == IRB.AMode) &&
1467 (IRA.ANumber == IRB.ANumber) &&
1468 (IRA.BMode == IRB.BMode) &&
1469 (IRA.BNumber == IRB.BNumber)
1470 ) {
1471 Queue(W, ((PC + 2) % M));
1472 } else {
1473 Queue(W, ((PC + 1) % M));
1474 };
1475 break;
1476 default:
1477 return(UNDEFINED);
1478 break;
1479 };
1480 break;
1481 /* SNE compares the A-value and the B-value. If there */
1482 /* is a difference, then the instruction after the next */
1483 /* instruction is queued. Otherwise, the next instrution */
1484 /* is queued. */
1485 case SNE:
1486 switch (IR.Modifier) {
1487 case A:
1488 if (IRA.ANumber != IRB.ANumber) {
1489 Queue(W, ((PC + 2) % M));
1490 } else {
1491 Queue(W, ((PC + 1) % M));
1492 };
1493 break;
1494 case B:
1495 if (IRA.BNumber != IRB.BNumber) {
1496 Queue(W, ((PC + 2) % M));
1497 } else {
1498 Queue(W, ((PC + 1) % M));
1499 };
1500 break;
1501 case AB:
1502 if (IRA.ANumber != IRB.BNumber) {
1503 Queue(W, ((PC + 2) % M));
1504 } else {
1505 Queue(W, ((PC + 1) % M));
1506 };
1507 break;
1508 case BA:
1509 if (IRA.BNumber != IRB.ANumber) {
1510 Queue(W, ((PC + 2) % M));
1511 } else {
1512 Queue(W, ((PC + 1) % M));
1513 };
1514 break;
1515 case F:
1516 if ( (IRA.ANumber != IRB.ANumber) ||
1517 (IRA.BNumber != IRB.BNumber)
1518 ) {
1519 Queue(W, ((PC + 2) % M));
1520 } else {
1521 Queue(W, ((PC + 1) % M));
1522 };
1523 break;
1524 case X:
1525 if ( (IRA.ANumber != IRB.BNumber) ||
1526 (IRA.BNumber != IRB.ANumber)
1527 ) {
1528 Queue(W, ((PC + 2) % M));
1529 } else {
1530 Queue(W, ((PC + 1) % M));
1531 };
1532 break;
1533 case I:
1534 if ( (IRA.Opcode != IRB.Opcode) ||
1535 (IRA.Modifier != IRB.Modifier) ||
1536 (IRA.AMode != IRB.AMode) ||
1537 (IRA.ANumber != IRB.ANumber) ||
1538 (IRA.BMode != IRB.BMode) ||
1539 (IRA.BNumber != IRB.BNumber)
1540 ) {
1541 Queue(W, ((PC + 2) % M));
1542 } else {
1543 Queue(W, ((PC + 1) % M));
1544 };
1545 break;
1546 default:
1547 return(UNDEFINED);
1548 break;
1549 };
1550 break;
1551 /* SLT (Skip if Less Than) queues the instruction after the */
1552 /* next instruction if A-value is less than B-value. */
1553 /* Otherwise, the next instruction is queued. Note that no */
1554 /* value is less than zero because only positive values can */
1555 /* be represented in core. */
1556 case SLT :
1557 switch (IR.Modifier) {
1558 case A:
1559 if (IRA.ANumber < IRB.ANumber) {
1560 Queue(W, ((PC + 2) % M));
1561 } else {
1562 Queue(W, ((PC + 1) % M));
1563 };
1564 break;
1565 case B:
1566 if (IRA.BNumber < IRB.BNumber) {
1567 Queue(W, ((PC + 2) % M));
1568 } else {
1569 Queue(W, ((PC + 1) % M));
1570 };
1571 break;
1572 case AB:
1573 if (IRA.ANumber < IRB.BNumber) {
1574 Queue(W, ((PC + 2) % M));
1575 } else {
1576 Queue(W, ((PC + 1) % M));
1577 };
1578 break;
1579 case BA:
1580 if (IRA.BNumber < IRB.ANumber) {
1581 Queue(W, ((PC + 2) % M));
1582 } else {
1583 Queue(W, ((PC + 1) % M));
1584 };
1585 break;
1586 case F:
1587 case I:
1588 if ( (IRA.ANumber < IRB.ANumber) &&
1589 (IRA.BNumber < IRB.BNumber)
1590 ) {
1591 Queue(W, ((PC + 2) % M));
1592 } else {
1593 Queue(W, ((PC + 1) % M));
1594 };
1595 break;
1596 case X:
1597 if ( (IRA.ANumber < IRB.BNumber) &&
1598 (IRA.BNumber < IRB.ANumber)
1599 ) {
1600 Queue(W, ((PC + 2) % M));
1601 } else {
1602 Queue(W, ((PC + 1) % M));
1603 };
1604 break;
1605 default:
1606 return(UNDEFINED);
1607 break;
1608 };
1609 break;
1610 /* SPL queues the next instruction and also queues the sum */
1611 /* of the Program Counter and Pointer A. */
1612 case SPL:
1613 Queue(W, ((PC + 1) % M));
1614 Queue(W, RPA);
1615 break;
1616 /* NOP queues the next instruction. */
1617 case NOP:
1618 Queue(W, ((PC + 1) % M));
1619 break;
1620 /* Any other opcode is undefined. */
1621 default:
1622 return(UNDEFINED);
1623 };
1624 /* We are finished. */
1625 return(SUCCESS);
1626 }
1627 6. Validation Suite
1628 6.1 Purpose and Requirements
1629 This validation suite exists to help developers test the compatibility
1630 of their Core War systems with the requirements set up in this
1631 standard.
1632 6.2 Assembly To Load File Test
1633 6.3 MARS tests
1634 6.3.1 DAT Tests
1635 6.3.2 MOV Tests
1636 6.3.3 ADD Tests
1637 6.3.4 SUB Tests
1638 6.3.5 MUL Tests
1639 6.3.6 DIV Tests
1640 6.3.7 MOD Tests
1641 6.3.8 JMP Tests
1642 6.3.9 JMZ Tests
1643 6.3.10 JMN Tests
1644 6.3.11 DJN Tests
1645 6.3.12 SEQ/CMP Tests
1646 6.3.13 SNE Tests
1647 6.3.14 SLT Tests
1648 6.3.15 SPL Tests
1649 6.3.16 NOP Tests
1650 7. Glossary and Index
1651 alphanumeric Any of the characters A-Za-z0-9 and the underscore.
1652 assembly file A file containing Redcode instructions.
1653 battle A contest between two or more warriors.
1654 core size See section 4.2
1655 Core War A game in which programs compete for control of a
1656 computer called a Memory Array Redcode Simulator.
1657 Core Wars More than one game of Core War.
1658 cycle See section 4.2
1659 Dwarf See sections 2.7 and 3.6
1660 initial instruction
1661 See section 4.2
1662 instruction A line of Redcode or object code indicating an action
1663 for MARS to execute.
1664 instruction limit
1665 See section 4.2
1666 loader A program or that part of a program which loads
1667 warriors into a MARS.
1668 load file A file containing a warrior's instructions in an
1669 assembled format. Any MARS program can be used with
1670 any and all Redcode assemblers which produce load
1671 files, allowing customized Core War systems.
1672 MARS An acronym for Memory Array Redcode Simulator. The
1673 computer in which Core War warriors run.
1674 newline A linefeed, carriage-return, or combination of linefeed
1675 and carriage-return. Whichever newline is native to
1676 the host operating system.
1677 object code The internal representation of a MARS instruction.
1678 read distance See section 4.2
1679 Redcode The assembly language of Core War.
1680 tournament A series of battles in which points, based upon the
1681 degree of success, are awarded for each battle and
1682 accumulated by each warrior (or programmer, depending
1683 upon the type of tournament).
1684 warrior A Redcode program.
1685 whitespace The space and tab characters.
1686 write distance See section 4.2
1687 A. Differences Between Standards
1688 A.1 Purpose
1689 This appendix lists some of the major differences between this standard
1690 and those standards which preceded it. The purpose is to help those
1691 who are familiar with a previous standard or standards to quickly
1692 understand those items which are new or have changed.
1693 A.2 Changes
1694 A.2.1 Assembly Files
1695 A comma is required for operand separation.
1696 Parenthetical expressions are allowed.
1697 There is a new pseudo-opcode, ORG, for specifying the first logical
1698 instruction.
1699 There is a new operator, modulus '%', for determining the remainder
1700 of integer division.
1701 A.2.1.1 ICWS'86 to ICWS'94 Conversion
1702 If a modifier is missing, it is assembled according to conversion
1703 rules that depend on whether the ICWS'86 or '88 standard is emulated.
1704 By default, a MARS should use the ICWS'88 conversion rules. Emulation
1705 of ICWS'86 is optional.
1706 Opcode A-mode B-mode modifier
1707 ---------------------------------------------------------
1708 DAT #$@<>*{} #$@<>*{} F
1709 MOV,CMP,SEQ,SNE # #$@<>*{} AB
1710 $@<>*{} # B
1711 $@<>*{} $@<>*{} I
1712 ADD,SUB,MUL,DIV,MOD # #$@<>*{} AB
1713 $@<>*{} #$@<>*{} B
1714 SLT # #$@<>*{} AB
1715 $@<>*{} #$@<>*{} B
1716 JMP,JMZ,JMN,DJN,SPL,NOP #$@<>*{} #$@<>*{} B
1717 ---------------------------------------------------------
1718 A.2.1.2 ICWS'88 to ICWS'94 Conversion
1719 The default modifier for ICWS'88 emulation is determined according
1720 to the table below.
1721 Opcode A-mode B-mode modifier
1722 ---------------------------------------------------------
1723 DAT #$@<>*{} #$@<>*{} F
1724 MOV,CMP,SEQ,SNE # #$@<>*{} AB
1725 $@<>*{} # B
1726 $@<>*{} $@<>*{} I
1727 ADD,SUB,MUL,DIV,MOD # #$@<>*{} AB
1728 $@<>*{} # B
1729 $@<>*{} $@<>*{} F
1730 SLT # #$@<>*{} AB
1731 $@<>*{} #$@<>*{} B
1732 JMP,JMZ,JMN,DJN,SPL,NOP #$@<>*{} #$@<>*{} B
1733 ---------------------------------------------------------
1734 A.2.2 Load Files
1735 A load file format is specified for the first time. (An object code
1736 did exist for ICWS'86).
1737 A.2.3 MARS
1738 There are no illegal instructions.
1739 The following addressing modes have been added:
1740 A-number indirect, A-number predecrement, A-number postincrement,
1741 and B-number postincrement.
1742 MUL, DIV, MOD, SNE, and NOP have been added.
1743 SEQ is an alias for CMP.
1744 Opcode modifiers have been added.
1745 Read and Write distance limitations have been imposed.