The 1979 CP/M OS— How Does It Look Today?

Dmitrii Eliuseev
8 min readFeb 14, 2021

I work as a software developer for many years, the very first systems I tried to write programs for, were MS-DOS and Windows 3.1. Once I got curious — how people used computers in the old times before I was born?

Now it’s easy to get an answer to this question — we can run this system on a modern PC. I will show how to set up the CM/M emulator and run some of the original software of that time.

Hardware

Before we start, it’s interesting to see what sort of hardware was in use. The average computer 40 years ago was something like this:

Source © https://en.wikipedia.org/wiki/Intertec_Superbrain

This machine has a 2 MHz Z80 CPU, 16 KB RAM (can be upgraded up to 64), two 170 or 340 KB floppy drives. As a top configuration, the 10 MB hard disk drive could be added. The price was about 2000–4000$ depending on the configuration.

How does it work? Let’s figure it out.

CP/M Setup

Nowadays there are several CP/M emulators available. For Windows, we can use iz-cpm, which can be downloaded for free from Github. Another good emulator, that I’ve used for Linux, is RunCPM.

Windows

For Windows, we need to download the iz-cpm, unpack it and run download.bat that included in the archive. Several CP/M software packages will be downloaded to the software folder. Then we can run the emulator and specify which folders will be mounted as virtual “drives”. For example, we can mount “cpm22” as an “A” drive and “ladder” game folder as a “B” drive:

iz-cpm.exe --disk-a software --disk-b software/ladder

The CP/M is ready to use:

Linux

For Linux, I was using the RunCPM emulator, which looks a bit more accurate in the terms of simulation quality. First, we need to compile RunCPM and set the CP/M environment:

sudo apt-get install ncurses-dev

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Dmitrii Eliuseev

Python/IoT developer and data engineer, data science and electronics enthusiast