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What was CP / M and why did it lose to MS-DOS?



CP / M operating system logo on a blue background

Before Microsoft and Intel dominated the PC market with a common platform, the CP / M operating system did something similar for small business machines in the late 1970s and early 1980s – until MS-DOS pulled the carpet from under it. Here’s more about CP / M and why it lost to MS-DOS.

What was CP / M anyway?

CP / M was a text-based operating system created by the American programmer Gary Kildall of Digital Research in 1

974. The initials initially stood for “Control Program / Monitor”, but Digital Research changed it to the more friendly “Control Program for Microcomputers” later.

As the price of microcomputers fell rapidly in the mid-late 1970s, CP / M, combined with the Z80 CPU, became a de facto standard platform popular among small business computers in the late 1970s and early 1980s.

CP / M and BASIC run on a Kaypro II computer.
CP / M and BASIC-80 run on a Kaypro II computer. Benj Edwards

CP / M was a console-based operating system, meaning that you interacted with it using a keyboard, typing in commands at a prompt. You have performed file operations with simple commands such as “PIP” (for copying files) by typing PIP A:=B:*.BAS and hit Enter. (This would copy all the BASIC files from drive “B:” to drive “A:”.) To start a program, type the program name and press enter. When done, reboot the machine or go back to the CP / M prompt.

One of CP / M’s major breakthroughs has been in handling basic input and output tasks with the underlying hardware, allowing application software to largely communicate with the operating system itself. This meant that CP / M applications were not necessarily tied to the specific hardware they were running on, and could be more easily translated between PCs from different vendors.

Popular applications for CP / M included WordStar (a word processor), SuperCalc (a spreadsheet application) and dBase (for databases). Other programs, such as AutoCAD and Turbo Pascal, emerged from CP / M and later became more successful after being later ported to MS-DOS.

What kind of computers did CP / M run?

Most computers with CP / M include an 8-bit Intel 8080 or a Zilog Z80 processor, although Digital Research later released a 16-bit version of CP / M for Intel 8086 machines called CP / M-86.

The Visual 1050 computer from a 1983 magazine ad.
The 1983 Visual 1050 ran an improved version of CP / M. Visual

Almost all computers using the industry standard S100 bus using an 8080 or Z80 could run CP / M. But an S100 bus was not necessary. CP / M shipped as the default operating system for hundreds of different computer models of all shapes and sizes. Popular CP / M computer vendors included Cromemco, Kaypro, Amstrad, Osborne, Vector Graphic, Televideo, Visual, and Zenith Data Systems.

Other computers – including some cheaper home machines – had CP / M capability as an add-on option, although it often required additional hardware to make it possible. In fact, Microsoft’s very first hardware product in 1980 was the Z80 SoftCard for the Apple II. Users could insert the card into their Apple II computer to give it a Z80 CPU that could run popular CP / M productivity applications.

A 1980 ad for the Microsoft Softcard running CP / M on an Apple II.
The 1980 Microsoft SoftCard enabled an Apple II to run CP / M. Microsoft

In 1982, Microsoft Chairman Bill Gates claimed that SoftCard customers represented the largest installation base for CP / M machines. Interestingly, around the same time, a new operating system based on CP / M – Microsoft’s MS-DOS – was rapidly gaining market share.

MS-DOS has borrowed a lot from CP / M

When IBM began developing its personal computer (the IBM PC 5150), the company first attempted to license CP / M, but Digital Research was uncomfortable with the proposed terms of the deal. So IBM turned to Microsoft, which licensed a product called 86-DOS from Seattle Computer Products (SCP). Several months later, Microsoft bought 86-DOS for $ 50,000.

86-DOS became IBM PC-DOS when it shipped with the IBM PC in August 1981. Later, Microsoft would sell PC-DOS under its own label as Microsoft MS-DOS.

When developing 86-DOS, the creator, Tim Paterson, looked heavily to CP / M for inspiration, borrowing the general architecture and nature of the command line. Here’s a list of some of the similarities between CP / M and MS-DOS:

  • A command prompt
  • Alphabetic drive letter names such as “A:”, “B:” and “C:”.
  • The 8 + 3 filename format (e.g. FILENAME.DOC)
  • The wildcard “*” and the matching “?”
  • Reserved file names such as PRN: (for printer) and CON: (for console)
  • “.COM” files for command executable files
  • Commands such as DIR, REN and TYPE

Gary Kildall was reportedly upset that PC-DOS mimicked CP / M so well and complained to IBM. With the concept of software copyright in its infancy, Digital Research declined to sue IBM and instead struck a deal where IBM would supply CP / M-86 as an option for its IBM PC machines. By then, PC-DOS was already shipping as the default operating system for the IBM PC, and it cost much less than CP / M-86 – about $ 40 instead of $ 240.

Kildall and Digital Research’s missed opportunity to initially license CP / M to IBM is often seen as one of the great tragedies in computing history – presumably, Kildall could have become a billionaire like Bill Gates had he just signed the deal with IBM. had signed. This juicy story has been enhanced by the press over the years. But when Kildall died in 1994, he wasn’t exactly a pauper: Novell bought Kildall’s Digital Research for a reported $ 120 million in 1991, making Kildall rich in the process. Still, it bothered Kildall that Microsoft enriched itself by imitating its signature product.

Why has MS-DOS won CP / M?

In establishing its operating system agreement with IBM in 1981, Microsoft negotiated a license that would allow the company to not only license PC-DOS to IBM, but also sell PC-DOS as a generic operating system (as “MS-DOS”). to vendors other than IBM.

Shortly after the release of the IBM PC, companies such as Compaq and Eagle Computer began selling clones that could run IBM PC software. In order to provide a compatible operating system for these cloning machines, they have licensed MS-DOS from Microsoft. Within a few years, hundreds of IBM PC clones filled the PC market and by 1986 MS-DOS became the most popular personal computing platform in the US.

MS-DOS beat CP / M for joining the success of the IBM PC platform. Microsoft fought hard to get MS-DOS on every PC shipped and keep it that way, and the company extended that practice into the Windows era.

What happened to CP / M?

In 1988 Digital Research created a clone of MS-DOS called DR-DOS in an effort to compete with Microsoft. It also sold a mouse-based graphical interface called GEM, which initially tried to replicate the Macintosh experience, but later competed with Windows. Both products received respect in the press, but neither really took off. Some argued that this was due to Microsoft’s anti-competitive tactics. After Novell bought Digital Research in 1991, CP / M languished with little development as MS-DOS continued to dominate the market.

Novell DR-DOS 6 box art
In a way, DR-DOS was the spiritual successor to CP / M. Novell

In 1996 Caldera bought the rights to Digital Research assets from Novell and continued to market DR-DOS. They also sued Microsoft for creating incompatibilities in MS-DOS to pull DR-DOS off the market (which was later settled out of court).

In 1997, Caldera released parts of CP / M 2.2 as open-source software, so hobbyists could keep working on it. Those copies are still available online for free. Today you can run CP / M in a browser thanks to an 8080 emulator written by Stefan Tramm.

In some ways, CP / M is one of Windows’ great-grandfathers, so bits of its lineage are baked into Windows conventions, such as drive letters and reserved file names. That way, CP / M never completely disappeared: its soul lives on in the DNA of products that billions of people use every day.

RELATED: Windows 10 still doesn’t allow you to use these filenames that were reserved in 1974




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