What Was CP/M, and Why Did It Lose to MS-DOS?

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CP/M Operating System logo on a blue background

Earlier than Microsoft and Intel dominated the PC market with a typical platform, the CP/M working system did one thing related for small enterprise machines within the late Seventies and early Eighties—till MS-DOS pulled the rug out from below it. Right here’s extra about CP/M, and why it misplaced out to MS-DOS.

What Was CP/M, Anyway?

CP/M was a text-based working system created by American programmer Gary Kildall of Digital Research in 1974. Its initials stood for “Management Program/Monitor” at first, however Digital Analysis modified it to the extra pleasant “Management Program for Microcomputers” later.

As the worth of microcomputers dropped quickly within the mid-late Seventies, CP/M, paired with the Z80 CPU, grew to become a de-facto commonplace platform that was standard amongst small enterprise computer systems within the late Seventies and early Eighties.

CP/M and BASIC running on a Kaypro II computer.
CP/M and BASIC-80 operating on a Kaypro II laptop. Benj Edwards

CP/M was a console-based working system, which implies that you interacted with it utilizing a keyboard, typing in instructions at a immediate. You carried out file operations utilizing simple commands reminiscent of “PIP” (for copying recordsdata) by typing PIP A:=B:*.BAS and hitting Enter. (This is able to copy all the BASIC recordsdata from drive “B:” over to drive “A:”.) To run a program, you’d kind this system title and hit enter. While you had been performed, you’d both reboot the machine or exit again to the CP/M immediate.

Considered one of CP/M’s key breakthroughs was in dealing with fundamental enter and output duties with the underlying {hardware}, leaving software software program to interface principally with the OS itself. This meant that CP/M functions weren’t essentially tied to the actual {hardware} they ran on and might be extra simply translated between PCs from completely different distributors.

In style functions for CP/M included WordStar (a phrase processor), SuperCalc (a spreadsheet software), and dBase (for databases). Different applications, reminiscent of AutoCAD and Turbo Pascal, originated on CP/M, and later grew to become extra profitable after being ported to MS-DOS later.

What Form of Computer systems Ran CP/M?

Most computer systems operating CP/M included an 8-bit Intel 8080 or a Zilog Z80 processor, though Digital Analysis later launched a 16-bit model of CP/M for Intel 8086 machines known as CP/M-86.

The Visual 1050 computer from a 1983 magazine ad.
The 1983 Visible 1050 ran an enhanced model of CP/M. Visible

Virtually all computer systems utilizing the industry-standard S100 bus that used an 8080 or Z80 had been able to operating CP/M. However a S100 bus wasn’t required. CP/M shipped because the default OS for hundreds of different computer models of every kind and sizes. In style CP/M laptop distributors included Cromemco, Kaypro, Amstrad, Osborne, Vector Graphic, Televideo, Visible, and Zenith Knowledge Programs.

Different computer systems—together with some lower-priced residence machines—featured CP/M functionality as an add-on possibility, though it typically required further {hardware} to make it doable to run. In truth, approach again in 1980, Microsoft’s very first {hardware} product was the Z80 SoftCard for the Apple II. Customers may plug the cardboard into their Apple II laptop to present it a Z80 CPU that might run standard CP/M productiveness functions.

A 1980 ad for the Microsoft Softcard that ran CP/M on an Apple II.
The 1980 Microsoft SoftCard allowed an Apple II to run CP/M. Microsoft

In 1982, Microsoft Chairman Bill Gates claimed that SoftCard prospects represented the biggest single set up base for CP/M machines. Apparently, round that very same time, a brand new working system primarily based on CP/M—Microsoft’s MS-DOS—was quickly gaining market share.

MS-DOS Borrowed a Lot from CP/M

When IBM started growing its Personal Computer (the IBM PC 5150), the agency first tried to safe a license to CP/M, however Digital Analysis didn’t just like the proposed phrases of the deal. So IBM turned to Microsoft, which licensed a product known as 86-DOS from Seattle Computer Products (SCP).  Some months later, Microsoft bought 86-DOS outright for $50,000.

86-DOS grew to become IBM PC-DOS when it shipped with the IBM PC in August of 1981. Later, Microsoft would promote PC-DOS below its personal label as Microsoft MS-DOS.

Whereas growing 86-DOS, its creator, Tim Paterson, seemed closely to CP/M for inspiration, borrowing its common structure and command-line nature. Right here’s a listing of some similarities between CP/M and MS-DOS:

  • A command immediate
  • Alphabetical drive letter names like  “A:,” “B:,” and “C:.”
  • The 8+3 file title format (for instance, FILENAME.DOC)
  • The wildcard character “*” and the matching character “?”
  • Reserved filenames reminiscent of PRN: (for printer) and CON: (for console)
  • “.COM” recordsdata for executable command recordsdata
  • Instructions reminiscent of DIR, REN, and TYPE

Gary Kildall was reportedly upset that PC-DOS mimicked CP/M so intently and complained to IBM. With the idea of software program copyrights in its infancy, Digital Analysis declined to sue IBM, and as an alternative made a deal the place IBM would offer CP/M-86 as an possibility for its IBM PC machines. By then, PC-DOS was already shipping because the default OS for the IBM PC, and it price far lower than CP/M-86—about $40 instead of $240.

The missed alternative by Kildall and Digital Analysis to initially license CP/M to IBM is commonly instructed as one of the great tragedies in computing historical past—supposedly, Kildall may have change into a billionaire like Invoice Gates if he had simply signed the cope with IBM. This juicy story has been amplified by the press through the years. However when Kildall died in 1994, he wasn’t precisely a pauper: Novell purchased Kildall’s Digital Analysis for a reported $120 million in 1991, making Kildall wealthy in the process. Nonetheless, it bothered Kildall that Microsoft enriched itself by imitating his signature product.

Why Did MS-DOS Win over CP/M?

When organising its working system cope with IBM in 1981, Microsoft negotiated a license that allowed the corporate to not solely license PC-DOS to IBM, but in addition to promote PC-DOS as a generic working system (as “MS-DOS”) to distributors apart from IBM.

Quickly after the IBM PC’s launch, firms reminiscent of Compaq and Eagle Pc started selling clones that might run IBM PC software program. To supply a suitable working system for these clone machines, they licensed MS-DOS from Microsoft.  Inside a number of years, a whole bunch of IBM PC clones stuffed the PC market, and in 1986, MS-DOS-based PCs grew to become the most popular personal computing platform within the U.S.

MS-DOS received out over CP/M as a result of it hitched a journey with the IBM PC platform’s success. Microsoft fought arduous to get MS-DOS on each PC shipped and to maintain it that approach, and the agency prolonged that observe into the Home windows period.

What Occurred to CP/M?

In 1988, Digital Analysis created a clone of MS-DOS known as DR-DOS in an try and compete with Microsoft. It additionally bought a mouse-based graphical interface known as GEM that originally sought to duplicate the Macintosh expertise, however later competed with Home windows. Whereas each merchandise earned respect within the press, neither actually took off. Some argued that this was attributable to anti-competitive tactics by Microsoft. After Novell bought Digital Analysis in 1991, CP/M languished with little growth as MS-DOS continued to dominate the market.

Novell DR-DOS 6 box art
In some methods, DR-DOS was the non secular successor of CP/M. Novell

In 1996, Caldera purchased the rights to Digital Analysis’s property from Novell and continued to market DR-DOS. Additionally they sued Microsoft for creating incompatibilities in MS-DOS to edge DR-DOS out of the market (which was later settled out of court docket).

In 1997, Caldera launched elements of CP/M 2.2 as open-source software program in order that hobbyists may proceed to work on it. These copies are nonetheless available for free online. Right now, you’ll be able to run CP/M in a browser because of an 8080 emulator written by Stefan Tramm.

In some methods, CP/M is without doubt one of the great-grandfathers of Home windows, so bits of its lineage are baked into the conventions of Home windows, reminiscent of drive letters and reserved file names. In that approach, CP/M by no means utterly disappeared: Its soul lives on within the DNA of merchandise that billions of individuals use every single day.

RELATED: Windows 10 Still Won’t Let You Use These File Names Reserved in 1974

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