TCOM80.TXT      Notes on TCOM for the 8080              by Tom Zimmer

  TCOM80 is a relatively simple version of TCOM for the 8080 processor.
It has been minimally tested, and is believed to generate programs that
will in fact run on a CPM system.  I say this is a simple version of the
compiler, because it was created as a test case to determine if TCOM
would support indirect threaded code generation.  TCOM did need a few
modifications to support this type of target.

  TCOM80 is compiled on top of my F-PC Forth, I am currently using
version 3.5505.  It will probably work on earlier version though.  TCOM
is currently at version 1.35, and that version is the one that should be
used with this version of TCOM80.

  The library for TCOM80 is essentially F83 Forth for the 8080.  As such
it imposes some interesting requirements on the compiler.  F83 supposes
that many variables are at specific places in memory, usually quite low
in the image. To get TCOM to generate a target program in this form, I
have had to make the IMAGE-INIT word in OPT80.SEQ compile some unusual
things.  If you look at it you will see that the image initialization
macro compiles some code, and several of the basic functions that F83
nees, and even compiles some variable and constants.   That is another
interesting caracteristic of TCOM80, its constants are actually in memory
like F83, not compiles as literals as in my other targets.  To get TCOM
to do this, CONSTANT and VARIABLE are redefined in OPT80.SEQ.

  Here is a list of files in TCOM80.ZIP that make up TCOM80 the compiler:

   MAKE80   BAT              \ batch file to build TCOM80.EXE
   TARGET80 SEQ              \ the load file for the following files
        LABEL80  SEQ         \ label forward reference resolution
        COMPILER SEQ    ***  \ not part of TCOM80, loaded from \TCOM\SRC
        ASM80    SEQ         \ an assembler for the 8080
        OPT80    SEQ         \ the target linkage to the compiler
        LIB80    SEQ         \ the F83 kernel is in the library
        INIT80   SEQ         \ default target application initialization

  The primary load file above is TARGET80.SEQ which loads the other files
and creates TCOM80.EXE in the same directory.  You can simplify the
generation of TCOM80 by using the MAKE80.BAT batch file.

  Here is a list of utility files that make development somewhat simpler:

        DMP      COM        \ A simple decompiler for TEST.CPM below
        DMP      SEQ        \ the source for the decompiler
        INC80    SEQ        \ a list to force inclusion of entire library
        DUMP     COM        \ just a simple file dump utility

  The file TEST.SEQ is a sample Forth program that TCOM80 can compile.
It is truely a very simple program, but it shows how TCOM will
automatically include what is needed to run your program.

        TEST     SEQ        \ a test source file for TCOM80
        TEST     SYM        \ symbol file renerated by TCOM80 with  /SYM
        TEST     LIN        \ a line pointer table for future disassembler
        TEST     CPM        \ a CPM style .COM file

  To compile TEST, enter the following line:

        TCOM80 TEST /SYM

  This will generate the remaining files listed above.  You can then see
what is in TEST.CPM by typing:  DMP <enter>

  DMP will automatically open the TEST files needed, and display a
decompiled dump of the contents of TEST.CPM.