CPM

The CP/M system comprises a custom CP/M BIOS and the BDOS (Basic Disk Operating System) and command line processor, CPP (Console Command Processor).

The Open Source status of CP/M has fairly recently been clarified so I feel safe including the Digital Research portions of the system in this Git repository.

BIOS

CP/M is a layered system with, effectivly, a hardware abstraction layer called the BIOS (Basic Input/Output System). This is the only component that needs to be modified to port CP/M to a new system. I've written a BIOS for my system that utilises the ZLoader/ZIOS core functions to provide I/O. In this way the BIOS itself is kept very small, maximising the Transient Programme Area (TPA) and reducing the development overhead.

Main features:

• Utilises the ZIOS core functions for I/O
• Understands the ZIOS virtual disk model, allowing access to any of the potential 1023 virtual 4MB 'disks'
• Leaves console I/O to the underlying system

Installing CP/M

The BIOS along with the CP/M code resides in the apps/cpm22 directory. A precomiled CP/M system is provided in the images top-level directory.