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nikitinprior / dF80 Public

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Restored F80 compiler code for CP/M

GPL-3.0 License
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README.md

 Restored F80 compiler code for CP/M

At one time, W. Cirsovius disassembled Microsoft assembler M80
(MACRO-80 3.44 09-Dec-81), MS-Linker L80 and several other programs
and posted the resulting code on his website. Unfortunately, the
Microsoft F80 compiler was not included in this list, and in 2014 I
made an attempt to fill this gap. I wanted to restore the code of one
of the latest compilers. For this reason, I chose FORTRAN-80 Ver. 3.4
Copyright 1978, 79, 80 (C) By Microsoft Created: 19-Feb-85. In
addition, this is one of the compilers that in the listing produces
code in Z80 assembler. At that moment, I did not yet know that this
particular compiler had a bug.

The Fortran-80 compiler consists of eight modules. Module boundaries
were determined by comparing the disassembled code of several F80.COM
executables. The modules differed slightly and were located in
different places. It is most likely that each of the modules was
placed in an individual file.

To speed up the compiler, a ready-made symbol table image with
Intrinsic functions FORTRAN language is copied from the data area to
upper memory. Then the necessary variables are initialized, the
compiler parameters are read, and it proceeds to the process of
processing the source code. The compiler is single-pass and for this
reason presents its own rules for the location of statements.

The file f80_ram.pdf shows the memory allocation during compiler
operation and the structure of the symbol table.

The disassembled source program is partly commented and resides in a
single f8.mac file. However, this does not prevent it from being
assembled into an object file using the command

m80 f8,f8=f8

and then compose

l80 f8,f8/n/e

The resulting f8.COM executable is completely identical to the
original F80.COM

Perhaps, based on this program, someone will find and fix the error
of this compiler. I keep the disassembled program for later
improvements.

I assume that for CP/M the FORTRAN compiler is 80 Ver. 3.4 Copyright
1978, 79, 80 (C) Microsoft Created: 19-Feb-85 was remade from the
executable code of the FORTRAN-80 Ver compiler. 3.4 Copyright 1978,
79, 80 (C) Microsoft Created: 01-Dec-80 for TRS-80.

It is most likely that the original compiler for TRS-80 was prepared
directly by Microsoft. Disassembly of the source file F80.CMD showed
the presence in the executable file of a set of traps placed by the
authors of the program to complicate its disassembly. Fragments of
superfluous code were excluded from the program modified for CP/M and
a number of other actions were performed to overcome the protection
against disassembly. A mistake was made in some place.

Who performed this transformation will remain unknown.

However, I disassembled the compiler F80 Ver. 3.44 for CP/M. The file
with the program has the name F.MAC. Compiling this file results in
the creation of an executable file completely identical to the
original program.

Andrey Nikitin

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Restored F80 compiler code for CP/M

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