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READ.ME FILE FOR THE MIXAL DISTRIBUTION
This is an assembler and interpreter for Donald Knuth's mythical MIX
computer, defined in:
Donald Knuth, _The Art of Computer Programming, Vol. 1: Fundamental
Algorithms_. Addison-Wesley, 1973 (2nd ed.)
This implementation was designed and written by Darius Bacon
<djello@well.sf.ca.us>, then ported to UNIX and debugged by Eric S. Raymond
<esr@snark.thyrsus.com>. Corrections to multiplication and division by
Larry Gately <lgately@rohan.btg.com>; see Notes.
Copyright (c) 1994 by Darius Bacon.
Permission is granted to anyone to use this software for any
purpose on any computer system, and to redistribute it freely,
subject to the following restrictions:
1. The author is not responsible for the consequences of use of
this software, no matter how awful, even if they arise
from defects in it.
2. The origin of this software must not be misrepresented, either
by explicit claim or by omission.
3. Altered versions must be plainly marked as such, and must not
be misrepresented as being the original software.
HOW TO USE IT
The program is a load-and-go assembler. To run the prime-numbers
example, for instance, type
mix prime.mix
and it will assemble and run the program. There are no special
debugging facilities yet, not even a core dump. It does print out the
processor registers upon termination.
DIFFERENCES FROM `STANDARD' MIXAL
There is one significant difference in the assembler format: Knuth
puts fields at fixed offsets on a line, while I separate them by
whitespace. (Purists may wish to fix this obvious bug.) Since the
ALF directive, which defines constant strings, becomes ambiguous when
delimited by whitespace, there's a new syntax to achieve the same
effect: instead of
ALF rime
use
CON " rime"
IMPLEMENTATION NOTES
The tape devices are currently unimplemented. (Use the 'card punch'
and 'printer' devices if you don't need mass storage. They're
automatically connected to standard input and output. (They could
easily be connected to named files, too, but I haven't put that in
yet.))
Floating-point instructions aren't implemented either. They weren't
covered in Volume I, which is all I've got so far.
This MIX is a binary machine. I think that was a mistake -- decimal
would make debugging enough nicer to compensate for the decreased
efficiency. When dumping internal values, it prints them in octal, so
you can get the field values by inspection.
Things to do are marked by a comment starting with **.
The program still needs more testing.
PORTING AND TESTING
The code is written in pure ANSI C. It is known to work in the
following environments:
OS Compiler
----------- ------------
BSD/386 gcc
AIX-3.2.5 gcc
DOS Watcom C
DOS Borland C
You can regression-test the interpreter with mixtest (under UNIX) or
test.bat (under DOS).
FILES
asm.[ch] A Silly Module
cell.[ch] Operations on MIX words (Cells)
charset.[ch] The character set
driver.[ch] Assemble a single source line
elevator.mix Sample code from Knuth vol. 1
io.[ch] Simulate MIX I/O devices
main.c Main program
Makefile Makefile for Unix
makefile.dos Makefile for Borland C++ under MS-DOS
manifest Guess!
mix.h Header for things needed all over the program
mixtest Regression-testing shell script
mystery.mix Sample program
mystery.out Its output
NOTES Notes on the MIX assembly language
op2c.awk Converts the table of instructions into a C array
opcodes The table of instructions
ops.inc The same, as a C array, for the awkless
parse.[ch] Parse an operand field
prime.mix Sample program, with notes on MIX assembly language
prime.out Its output
READ.ME General info
run.[ch] Simulate the MIX machine
symbol.[ch] The symbol table
test.bat Regression-testing DOS batch file
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