CP/M is 50

August 5, 2024 1:11 AM

The Register reports that CP/M, the "Control Program for Microcomputers," has turned 50 years old! Amstrad released a CP/M laptop, using 720K 3 1/2-inch disks, as late as 1993, as demonstrated by Poking Technology in this Youtube video (19 minutes). CP/M used single-letter designations, like "A:", to represent disk drives. MS-DOS picked that convention up, where it survived into Windows 95 and NT, and has remained a part of Windows throughout its life up to this very day.

A short history of CP/M. CP/M was made completely open source in 2022. Here's a wiki page on ethw.org about CP/M and its legacy. CP/M's creator Gary Kildall passed away in 1994.

The first cross-platform OS for microcomputers, it was created in 1974 by Dr. Gary Kildall as a (relatively) simple disk-oriented command-line OS for Intel 8080 and Z80 microprocessors, who founded Digital Research to sell it. By the way! Before it had to become straight-laced to convince businesses to support it, Digital Research was known as Intergalactic Digital Research.

CP/M had a surprisingly long life. One of the Commodore 64's original selling points was a cartridge with a Z80 chip in it that would allow the machine to run CP/M, and the Commodore 128 had a built-in Z80, and could run it directly from disk.

The memory-resident kernel of CP/M takes up about 3 1/2 kilobytes! The OS which would eventually be bought by Microsoft and refashioned into MS-DOS for Intel's 8086 processor got its start as a reimplementation of CP/M's API calls.

Last year, cj7hawk at the Vintage Computer Federation Forums wrote from scratch LokiOS, a new implementation of CP/M for bespoke hardware.

The CRISS is a single-board computer that emulates a Z80 and can run CP/M, uses an SD card for its disk drive, and can use current-day monitors and PS/2 devices.

Here's Computerphile on the history of CP/M (10m), and using it now (6m). Here's The Phintage Collector on CP/M-86, a variant for 8086 machines (13m).

Here's an episode of the Computer Chronicles that has Gary Kildall on to talk about the development of CP/M and a multitasking successor (9m).

For those wanting to learn the technical details (or wish to be reminded), The Unofficial CP/M Website survives to this day!

One of the biggest supporters of CP/M was Infocom, which released versions of many of their games on that platform. Here is Zork played on an Altair 8800 running CP/M (1m).

Around 2018, Sydney Smith wrote a Z80 emulator for Windows with a version of CP/M included.

This post is dedicated to all of Metafilter old-time computer users, both those still here, and those who are gone, either because they no longer post, or have moved on to that great mainframe in the sky.

posted by JHarris (8 comments total)

In the 80s, I only knew CP/M as that strange 'other' mode that the Commodore 128 supported. The one that could actually utilize the sharp 80 column mode, if you had the right monitor hook-up. I recall having a CP/M boot disk and booting into that sharp green and grey screen, but lacking any actual software or anything to *do*, not much of it went anywhere. By 1990 I'd moved on to the PC and MS-DOS, so it was a memory in the rear view mirror by then. Guess things would have been different if I had stumbled upon it by one of its killer apps (Lotus 123? something like that.)
posted by Rhomboid at 1:31 AM on August 5 [1 favorite]

Fantastic post, super interesting!
posted by Dysk at 3:04 AM on August 5

CP/M is probably the first operating system I ever booted, on my dad's mid 80's SORD work computers. It's what I first played Colossal Cave Adventure on and has a place reserved in my heart as a result. I'm trying to remember the names of programs my dad used for actual work on it but am struggling. PIPS was one I think but damned if I know what it did.
posted by deadwax at 3:20 AM on August 5 [1 favorite]

PIP, or Peripheral Interchange Program, is like CP/M's copy command, but it can also print things?
posted by JHarris at 3:45 AM on August 5 [1 favorite]

This page might also fill in why some find CP/M appealing even now, above even Linux, because with CP/M the user is able to actually understand everything that happens on their machine. It's still awfully limited, mind you, but it's an appealing thought.
posted by JHarris at 3:53 AM on August 5

CP/M ran the first ‘real’ computers I used back in the mid-eighties. At the time, there were several Danish computer companies, so I remember programming small programs in MicroProlog and PolyPascal (which would later become Turbo Pascal) on the BUTLER, and learning Comal80 and word processing on the larger Regnecentralen Piccoline. Can’t say I remember much CP/M, though I undoubted would transfer some skills when later moving to MS-DOS.
posted by bouvin at 3:56 AM on August 5 [1 favorite]

This brings back vague memories of a long-ago essay extolling the virtue of CP/M over MS-DOS, poetically titled "The Captain and the Lady," by Piers Anthony.
Unfortunately, that nomenclature is all that I can recall, and searching hasn't turned up either the source or citations.
posted by cheshyre at 4:19 AM on August 5 [1 favorite]

My very first computer was an Apple II+, for which I bought a Z80 co-processor card that would enable it to run CP/M because CP/M was needed to run WordStar, and back then WordStar was the shit!
posted by Naberius at 5:09 AM on August 5 [1 favorite]