MS-DOS Programming (in C)
=========================

I  sometimes  use   my  MS-DOS  laptop  (the  PSION   MC600)  for  some
semi-serious tasks. For  example, at work we have a  project related to
chloride ingress in reinforced concrete. This is a complicated task but
there  are  also  approximate  solutions which  use  relatively  simple
formulas. We are using one such approximate solution for some purposes.

There  has been  a  simple  C program  which  for  the above  mentioned
solution. Nothing special: it reads few numbers, uses some formulas and
then produces  some textual output. The  same thing can be  done with a
spreadsheet and/or software like GNU  Octave (or Matlab). The reason to
write the C code was need to  use it as a plug-in for our probabilistic
software.

Well, most of these information are not important. But I wanted to test
the program  (better said: to  play with  various inputs) and  for this
task there should  be no need for powerful computer.  So I have started
to compile the  code for my MC600  (that is, for the MS-DOS  3.3 on the
8086 CPU).

The POWER C  is an ANSI89-compatible compiler, and a  strict one. I was
surprised how  GNU-isms we  have in  our code.  There were  things like
declarations inside procedures or stiff like (30/12) in declarations of
variables (among  other things). So  I had  to fix these  things. After
that it was possible to compile the program.

The POWER C produces relatively big executables. The - so called - disk
space on  the MC600 is  very limited  (I have the  1 MB PSION  SSD disk
here). So I often use the LZEXE  [2] to compress the executables. It is
a very  handy tool by Fabrice  Bellard (yes, that person  who wrote the
QEMU).

After all  these steps the program  actually runs. And it  runs without
problems (even the results are correct)!


References:
[1] http://www.mixsoftware.com/product/powerc.htm
[2] https://bellard.org/lzexe.html