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1994-12-23
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The MADgic Core
Core War for the Amiga
©1992 Mark A. Durham
Table of Contents
Introduction 3
A Brief History 4
Description 6
Quick Start 8
Redcode 12
ASR
26
MARS
29
Menus 32
2
Introduction
Welcome to The MADgic Core, Core War for the Amiga. Core
War, dubbed "the Programmer's Game of Choice", is an
exciting dual of survival between programs within your
computer. The MADgic Core brings you all of the tools
necessary to do combat.
This manual will provide you with a basic understanding (or
reminder) of Redcode assembly language programming as well
as a complete description and explanation of the use of the
Redcode assembler,
MARS
executive program, and tournament
manager.
3
A Brief History
Core War was first defined by D. G. Jones and A. K. Dewdney
of the Department of Computer Science at the University of
Western Ontario in March of 1984 in their "Core War
Guidelines". Core War was introduced to a larger public via
Dewdney's regular columns in
Scientific American
, "Computer
Recreations", starting in May of 1984, and a collection of
those columns (and others) in Dewdney's book -
The Armchair
Universe.
4
Since that time, Core War has been in the hands of The
International Core War Society. The ICWS has produced two
standards over the years: ICWS'86 and ICWS'88. Neither
varies too far from the original document, nor are they much
different from each other. This is a partial testament to
the soundness of the careful initial thought and effort that
went into the project as well as the difficulties of
agreeing on new ideas.
5
Description
Core War is a game which combines programming skills and
strategic thinking. The object is very simple: devise and
implement a program more capable of surviving and more
capable of killing than your opponent's. It is much like
deciding on an opening game, middle game, and end game in
chess and irrevocably committing robots to play the game
that way for you. The robots won't make any mistakes, but
if your strategy was wrong, you lose.
Note that although Core War encompasses much of Artificial
Life and computer virus theory, there is absolutely no
6
danger to your computer or anyone else's computer from Core
War. The MADgic Core is a completely contained, stable
environment. You quit, and it is gone.
Core War consists of two parts: the language and the
simulator. The language is known as Redcode. It is an
assembly language and is described in full in the following
section. The simulator is known as
MARS
(for Memory Array
Redcode Simulator). The MADgic Core consists of
ASR
, a
symbolic Redcode assembler,
MARS
and other simulators, and a
collection of Redcode programs from previous ICWS
tournaments. Also included is a tournament manager
program.
7
Quick Start
This section describes the basics of how to write, assemble,
and run Redcode programs.
Insert your copy of The MADgic Core disk into a disk drive.
Assuming you still have the Notepad utility on your Workbench
disk, double-click on the IMP.s icon. This will open up a
Notepad note. If you do not have the Notepad utility on your
Workbench disk, you can view the contents of the file with any
standard text editor or word processor.
8
The note is actually a Redcode source file for a program called
IMP. The appendix ".s" is necessary on all source files, hence
this note is named "IMP.s". You do not need to make any changes
to this file, so just close the Notepad window for now.
Select the IMP.s icon. While the IMP.s icon is selected, shift
double-click on the
ASR
icon. A window will open up and a
question will be displayed. Answer the question by typing a 'Y'
followed by <RETURN>. A listing of the file will be displayed in
the window followed by a symbol table.
9
A request to hit the <RETURN> key is the last thing in the
window. When you have finished looking at the window, hit
<RETURN>. The window disappears.
Double-click on the
MARS
icon. A blank and borderless window
will open in a new screen. A requester will appear. Select "OK"
and the requester will disappear.
Select "Load" from the "CORE" menu. A requester will appear.
Select the left uppermost text gadget and type "IMP". Select the
left lowermost text gadget and type "IMP". Select "OK" and the
requester disappears and the programs are loaded.
10
Select "Go" from the "Control" menu. You should see an
advancing white square lead by a light blue square on the top
half of the screen and an advancing black square lead by a dark
blue square on the bottom half of the screen.
After a while, select "Stop" from the "Control" menu. Next,
select "Close" from the "Core" menu. Congratulations! You have
successfully assembled and run a Core War program!
11
Redcode
Redcode is the language of Core War. Redcode is an assembly
language. This means that each single statement in Redcode
will be assembled into a single machine language
instruction. Because there is no Core War machine as of
yet, we use a simulator to run the machine code instead.
There are eleven types of machine instruction. Each of
these types has a corresponding three-letter opcode in
Redcode. These opcodes are:
DAT
,
MOV
,
ADD
,
SUB
,
CMP
,
JMP
,
JMZ
,
JMN
,
DJN
,
SLT
, and
SPL
. These opcodes are meant to be
indicative of what the instruction will do.
DAT
is storage
12
for data,
MOV
moves data,
ADD
and
SUB
add and subtract data,
etc. These opcodes will be explored further below.
Each opcode can be followed by one operand or two operands
seperated by a comma. Operands are merely that part of an
instruction which holds the data operated on by the opcode,
or tells the opcode where to find the data. We usually
indicate generic operands as
A
and
B
.
Operands can be divided up into two seperate parts: the mode
indicator and the address. The mode indicators are for
immediate, the # (octothorpe), for direct, _ (space) or $
(dollar sign), for indirect, @ (commercial 'at'), and lastly
13
for pre-decrement indirect, < (left angle bracket). The
mode indicator tells the opcode whether the address is data
(immediate), an offset to the data (direct), an offset to an
offset to the data (indirect), or an offset to one more than
the offset to the data (pre-decrement indirect).
The address of a Redcode instruction is special. All
addresses in Core War are relative to the currently
executing instruction and modulo the memory size of our Core
War machine. This means that if the memory size of our
machine is 8000, an address of -2 is really 7998; an address
of 9256 is really 1256.
14
Fortunately,
ASR
is a symbolic assembler. What this means
is that most of the time you will not have to bother writing
addresses as numbers. Each statement of interest to you may
be proceeded with a label.
A
label may be any word other
than the opcodes and any other labels.
Lastly, there are things you can write in Redcode which do
not have a direct relationship to the machine instructions.
These include comments and pseudo-ops, opcodes which
instruct the assembler to do something rather than produce a
machine instruction.
15
In order to better understand Redcode, it is best to look
first at a few Redcode programs. The smallest useful
program is Imp. Here we have an expanded version to
demonstrate all of the important aspects of Redcode.
; Imp.s
; by A. K. Dewdney
;
Imp MOV Imp, Imp+1 ; That's all!
END
16
The lines which begin with a semicolon are comment lines.
These lines mean nothing to the Redcode assembler, so they
are ignored. You can use comments to keep track of who
wrote a program, when it was written, what kind of algorithm
it implements, etc.
There is only one real instruction line in the program. It
starts with the label
Imp
. The opcode is
MOV
. Both the
A
and
B
operands are of direct mode. You will note that this
instruction is followed by a semicolon and another comment.
17
Of interest is the fact that in the
A
address is the
Imp
label again. The
Imp
label is also in the
B
address along
with a plus sign and a one. Because the offset from this
instruction to this instruction is zero, the statement could
have been written much more simply as
MOV
0, 1.
Finally, the pseudo-op
END
instructs the assembler that we
are at the logical end of this file and it may stop
assembling now. The only other pseudo-op of interest is
EQU
. These pseudo-ops, as well as the opcodes, are
discussed in greater detail below.
18
DAT
A
B
This instruction is used for storing data. However, upon
trying to execute a
DAT
instruction, the current task is
stopped and removed from the queue. When all of one
player's tasks have been stopped and removed from the queue,
that player has lost.
MOV
A
B
If the
A-mode
is immediate, the
A-value
is placed in the
B-
operand]0m of the memory location specified by the
B-operand
.
Otherwise, the entire statement referred to by the
A-operand
is moved to the address specified by the
B-operand
.
19
ADD
A
B
If the
A-mode
is immediate, the
A-value
is added to the
B-
operand of the memory location specified by the
B-operand
.
Otherwise, both operands are added: the
A-operand
is added
to the
A-operand
of the memory location specified by the
B-
operand]0m and the
B-operand
is added to the
B-operand
of the
same memory location.
SUB
A
B
SUB
is just like
ADD
except the operands are subtracted
instead of added.
20
JMP
A
B
This task will continue processing at the memory address
specified by the
A-operand
, instead of the next statement as
usual.
JMZ
A
B
If the
B-operand
evaluates to zero, a jump will occur just
as in
JMP A B
, otherwise the task will continue with the
next statement as usual.
21
JMN
A
B
If the
B-operand
does not evaluate to zero, a jump will
occur just as in
JMP A B
, otherwise the task will continue
with the next statement as usual.
CMP
A
B
If the
A-mode
is immediate, the
A-value
is compared to the
evaluation of the
B-operand
. Otherwise, the entire
statement referenced by the
A-operand
is compared to the
entire statement referenced by the
B-operand
. If the
comparison is equivalent, the next statement is skipped.
22
SLT
A
B
If the
A-mode
is immediate, the
A-value
is compared to the
B-operand
specified by the
B-operand
. Otherwise, the
B-
operand specified by the
A-operand
is compared to the
B-
operand specified by the
B-operand
. If the comparison is
less than, the next instruction is skipped. Note that
nothing is less than zero.
DJN
A
B
The value referenced by the
B-operand
is decremented and
compared to zero. If it is not zero, a jump is taken just
as in
JMP
A
B
.
23
SPL
A
B
The task starting at the address specified by the
A-operand
is added to the task queue. Note that this new task is
placed between the current task and the next task. Also
note that all other tasks will execute once before this task
will execute for the first time.
EQU A
EQU
is a pseudo-op which associates everything to the right
of itself with the label of the left of itself. So the
result of the statement
X EQU A
is the same as replacing
every occurence of
X
with the text
A
.
24
END A
END
is a pseudo-op which indicates the last logical line of
Redcode. Additionally, if there is an operand it indicates
which statement is the first to be executed. If there is no
operand, execution will start with the first statement.
25
ASR
ASR
, the assembler, can be started from either the CLI or
the Workbench. The assembler accepts as a source file any
plain ASCII text file such as that produced by the Notepad
(with Global Fonts), a text editor, or a word processor
(again, when saved as plain ASCII). The name of the source
file must end with a ".s" in order for
ASR
to recognize it.
There are many example source files presented on the disk.
To invoke
ASR
from the CLI, type "ASR" followed by the name
of the source file. The name you type after "ASR" need not
have the ".s" appended to it, as in "ASR IMP", but
ASR
will
26
still look for a filename ending in ".s"; "IMP.s" in this
example.
If you want to list the assembler output from the CLI, place
a " -l " (a minus sign followed by a lowercase L) between
"ASR" and the name of your source file. If you want to send
the listing to the printer, type " >prt: " just after "ASR"
and before " -l ". If you want to send the listing to
another file, replace "prt:" with the name of your list file
in the example above.
27
To invoke
ASR
from the Workbench, select the icon of the
source file you want to assemble and shift double-click on
the
ASR
icon while the source file icon is still selected.
If you want to list the assembler output to the window, type
"Y" followed by the <RETURN> key.
If you want to list the assembler output to the printer,
type "P" followed by the <RETURN> key. If you do not want
to list the file, type "N" followed by the <RETURN> key. In
any case, you will need to hit the <RETURN> key after the
assembly is complete in order for the window to close.
28
MARS
MARS
can be started from either the CLI or the Workbench.
To start
MARS
from the CLI, type "MARS". Any parameters
will be ignored.
To start
MARS
from the Workbench, double-click on the
MARS
icon. Alternatively, select one or two files, and shift
double-click on the
MARS
icon while the file(s) are still
selected. Any selected files will still need to be loaded,
but the file name(s) will be already in the load requester
text gadget(s).
29
Default core size, maximum number of tasks, maximum number
of cycles, colors, and version can all be set from the
Workbench. Select the
MARS
icon and select
Get Info
from
the Workbench menu. In the Tool Types, you will see these
options.
Add or change
Core Size=
to any of the menu choices.
Tasks=
can be any number, as well as
Cycles=
.
Version=
should be
either
86
or
88
.
30
Color=
sets all the colors. They are listed as eight sets
of three hexidecimal numbers (0-F) seperated by vertical
bars (|). Each number represents one fifteenth of a percent
of red, green, or blue in that order. The order is
background,
MOV A
,
MOV B
, executing
A
, executing
B
,
DAT A
,
DAT B
, and
SPL
.
31
Menus
This is a reference section for the menu items you will find
in
MARS
.
Core
The Core menu is available whenever there are no requesters
open in the
MARS
window and there are no battles currently
running.
Size
The Size item has subitems of 2000, 4000, 8000,
8192, 16000, 32000, 64000, and 128000. Each of
32
these subitems selects a core size. Not all core
sizes may be available to you. The more memory
you have, the larger the core size you can
accomodate.
The arrow indicates which core size you have
selected. Just because you are able to select a
core size does not mean that you can actually run
programs in a core of that size. In the event you
do not have enough memory for a core of your
selected size, a requester will appear with "Not
Enough Memory" when you try to load your programs.
33
Load
The Load item brings up a requester with two text
gadgets on the left and two integer gadgets on the
right.
Type the names of the programs you want to load
into the text gadgets on the left and type the
locations to load the programs to in the adjacent
integer gadgets on the right. Then select "OK".
If you did not intend to bring up the load
requester, then select "Cancel".
34
Alternatively, you can specify which file to load
by clicking on the "A" or "B" gadget for Player A
or Player B respectively. Clicking on either of
these gadgets brings up a file requester.
You can specify what volume by volume name,
assigned name, or device. You can then enter
directories by clicking on the appropriate name.
"Parent" will take you up to the parent directory.
You can change the extension filter by double-
clicking on "Filter", or just turn it on/off with
a single click. The default extension filter is
35
".o" since
MARS
can load only those files which
end in ".o".
The load requester can be brought up at any time
by holding down the right Amiga key and the L key
at the same time. You must load in programs
before you can access the "Control", "Trace", or
"Memory" menus.
36
Max Cycles
The Max Cycles item brings up a requester with an
integer gadget. Select the integer gadget and
type in the maximum number of cycles you want
executed per side before declaring a draw, then
select "OK". If you do not want to change the
maximum number of cycles from that originally
displayed in the requester, select "Cancel".
Max Tasks
The Max Tasks item brings up a requester with an
integer gadget. Select the integer gadget and
type in the maximum number of tasks you want to
37
allow per side, then select "OK". If you do not
want to change the maximum number of tasks from
that displayed in the requester, select "Cancel".
Color
The Color item brings up a requester with several
gadgets in it. Select the item for which you wish to
change the color, either player
A
, player
B
,
MOV A
,
MOV
B,
DAT A
,
DAT B
, or
SPL
. Then adjust the level of red
in that color by sliding the knob in the gadget next to
the "R". Similarly, you can adjust the level of blue
or green by sliding the knob in the gadget next to the
"B" or the "G".
38
When you are finished with any item, select any other
item and adjust its colors in a like manner. When you
are finished adjusting colors, select "OK" if you want
to use your new colors, or select "Cancel" if you want
to use the colors that were in the requester when you
first selected "Color".
Version
You can select from running the ICWS'86 standard
version of Core War and the ICWS'88 version of
Core War. Only ICWS'88 is described in this
document.
39
Quit
The Quit item ceases any battles, closes all open
windows, and closes the screen. You can also quit
at any time by holding down the right Amiga key
and typing "Q" at the same time. You must restart
MARS
in order to use any of the other items after
selecting "Quit".
40
Control
The Control menu is only available if programs have been
successfully loaded into the core and no requesters are in
the
MARS
window.
Stop
The Stop item is only available if there are
programs currently battling in the core. Stop
ceases the current battle and enables the Core
menu. Stop is also invoked whenever the right
Amiga key is held down along with the S key.
41
Step
The Step item is only available if there are no
programs currently battling in core. Step
executes the next instruction from each warrior.
Step is also invoked whenever the right Amiga key
is held down along with the T key.
42
Continue
The Continue item is only available if there are
no programs currently battling in core. Continue
starts execution of all warriors in core from the
next instruction of each warrior. Continue is
also invoked whenever the right Amiga key is held
down along with the C key.
Go
Go is just like Continue except it is more
psychologically satisfactory for starting battles.
43
Trace
The Trace menu is only available if programs have been
successfully loaded into the core and no requesters are in
the
MARS
window.
Open
The Open item has three subitems, "A", "B", and
"Both". If you select "A", only program A will be
traced. If you select "B", only program B will be
traced. If you select "Both", then both program A
and program B will be traced.
44
Upon selection, a window with the title "Trace
Window" appears. The trace window can be moved
about, to the front and back, and sized.
As instructions are executed by
MARS
, they appear
in the trace window. Player A instructions appear
in white (assuming default colors) and Player B
instructions appear in black. The absolute
address, the opcode, and the two operands are each
displayed.
Close
The Close item closes the trace window.
45
Address
The Address item has three subitems, "Relative",
"Negative", and "Absolute". If Relative is
selected, addresses in operand fields will be
relative to the current instruction.
If Negative is selected, addresses in operand
fields will be relative to the current
instruction, but addresses larger than half of the
core size are displayed as negative addresses. If
Absolute is selected, addresses in operand fields
are displayed as absolute addresses.
46
Memory
The Memory menu is only available if programs have been
successfully loaded into the core and no requesters are in
the
MARS
window.
Open
The Open item opens the memory window. The memory
window can be moved and sized. It will display as
many lines as will fit completely in the window.
The portion of memory currently displayed in the
memory window can be changed by sliding the knob
47
in the right hand gadget. Sliding the knob up
moves toward memory location zero. Sliding the
knob down moves toward memory location (Core Size
- 1). The up-arrow gadget will move one memory
location closer to zero. The down-arrow gadget
will move one memory location closer to (Core Size
- 1).
Pointing at any point in the
MARS
window and
clicking the left mouse button will start the
memory display at that location. The memory
window is not dynamically updated. If you want to
be sure that what is displayed in the memory
48
window is what is currently in memory, make sure
that the current battle is stopped and then select
the sizing gadget of the memory window. It is
unneccessary to actually change the size of the
memory window.
Close
The Close item closes the memory window.
Address
The Address item behaves exactly as the Address
item under the Trace menu does.
49
Window
The Window Menu is available whenever there are no
requesters open in the
MARS
window.
To Front
The To Front item moves the
MARS
window to the
front of the
MARS
screen. Any window which is
also open in the
MARS
screen, such as the trace
window and/or the memory window, will temporarily
disappear behind the
MARS
window.
50
To Back
The To Back item moves the
MARS
window to the back
of the
MARS
screen. Any window which is also open
in the
MARS
screen, such as the trace window
and/or the memory window, will reappear from
behind the
MARS
window.
51
Screen
The Screen menu is available whenever there are no
requesters open in the
MARS
window.
To Front
The To Front item moves the
MARS
screen to the
front of the display.
To Back
The To Back item moves the
MARS
screen to the back
of the display.
52
