Zeno's PC DOS Assembler Freeware

From 1983 until 1987, I worked in the IBM European PC organisation, which handled the introduction of the IBM PC into Europe. When I first started writing software for the PC, my machine had 128K of memory and one 180KB diskette drive - back then, programs had to be small!

The rather ancient PC DOS Assembler programs here include:


The most popular PC tool I ever wrote is called CABLE - Compare And Browse with Limited Editing - and it's a small PC DOS program (it also runs in a DOS Prompt in Windows 95, 98 and NT) that lets you browse and patch files. There are three things about CABLE that made it popular:

  1. it's small (17K) and fast
  2. it's simple and obvious to use (it has on-line help)
  3. it can handle files up to 100 MB in size no matter how much memory you've got (it could handle files that size on a 128K PC XT).

Here's a screen image of CABLE in action, comparing two binary files (actually, two different versions of itself):

This ZIP file contains:

If you set up a shortcut to run CABLE from Windows, make sure the working directory is set to the one containing the help file. If you want to be able to invoke CABLE from a DOS prompt, then also you'll need to make sure the current directory is set to the one containing the help file before you start CABLE. Alternatively you can patch CABLE (using CABLE of course) so that it can locate the help file wherever it is.

2014 Note: BAFFLE, a java version of CABLE, which runs under OSX, Windows or Linux, is available here.


FTL is a very small (5K) version of John Horton Conway's LIFE that runs in medium resolution CGA mode, giving a 200 by 200 cell universe. Here's a screen shot:

This ZIP file contains:

  1. the program, FTL.COM
  2. its source code, FTL.ASM
  3. FTL.HTM - an HTML document about FTL
  4. a sample colony, FTL.BOX


MULCH acts just like an editor given a succession of global change commands. It's a stream editor, designed to be a fast batch way of making several changes to a file in one go.

This ZIP file contains:

  1. the program, MULCH.COM
  2. its source code, MULCH.ASM
  3. MULCH.HTM - an HTML document about MULCH


XCUT performs a very simple parsing operation on a file. It splits the file into three parts:

  1. the part before a given repetition of a given (hex) string
  2. the given string
  3. the part after the given string

The output file can be made up of any combination of these three parts (though always in the order 1,2,3). By default it's just 1.

This ZIP file contains:

  1. the program, XCUT.COM
  2. its source code, XCUT.ASM
  3. XCUT.HTM - an HTML document about XCUT