Disk Operating System

On the website from Amigan Software I found a binary of a Disk Operating System for the Central Data board. Just the binary, no sources and no manual. So what do you do? You reverse-engineer.

Using the DASMx disassembler, lots of puzzles, conjecture and hours of work I re-created the sources and manual for CD DOS. I believe that Central Data were the original authors, but I'm not sure.

CD_DOS.2650

Fully documented source code, with lots of comments to explain how everything works. It works fine with my assembler (found elsewhere on this website).

CD_DOS.list

Assembler output listing. Same as the source, but with the addresses and code.

Builtins.txt

A description of the built-in commands of DOS.

Notes.txt

Various other helpful notes. Read these first.

CD DOS uses a fairly sophisticated (for its time) security system. See Notes.txt for my understanding how all of this works. Two DOS commands are CCODE and ICODE. The first controls access to files. The second also controls access to files, but provides a "second chance" when the access control set by CCODE fails. I guess that CCODE stands for Change Code: the codeword to allow file changes. And that ICODE stands for Inspect CODE: the codeword to allow the user to read and use the file. If anyone know more about these commands I would love to hear it.

I am currently working on correcting and augmenting CD DOS, including some external utilities to format a disk, copy files and to modify user accounts and password.

This page is part of my P1 restoration website.

Eelco Vriezekolk.
Questions or remarks? Send me an email on eelco[at-sign]ztpe[little dot]nl