Why was CP/M Important?

This document (c)Copyright Herb Johnson 2011 all rights reserved. Updated OCt 13 2011.
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On October 15th 2007, I lectured about CP/M for a university class studying and working on "classic" computer history and restoration. "Classic" refers to primarily personal computers of the 1970's and 80's. I enjoyed the experience, and it was a chance to see my work in progress on CP/M history from their point of view. I hope they got some benefit from the lecture, and can benefit from my Web site on the subject of Gary Kildall's work on CP/M and its subsequent development by him and others in the 1970's. But, I think my presentation was likely incomplete from their point of view, from a time well after that period. I was asked questions about current use of CP/M, and related questions about the modern context of CP/M. Also, I was asked a question: "why didn't the IBM PC first use CP/M?" - a reasonable question, which I did answer fairly completely. The IBM PC is also part of the subsequent story of CP/M and Digital Research.

Today the IBM PC story often overshadows the story of Digital Research and CP/M, unfortunately. That fact was a major reason for my work on CP/M and for my lecture. But most of my work is only on the first half of the story. This Web page is an overview of the other half of the DRI story, around and after the time of the IBM PC in 1981.

Herb Johnson

CP/M in the late 70's as a major product

Kildall began CP/M in 1973 or '74, not long after microprocessors were first developed. Much of my DRI web site covers development of CP/M and related products by Gary Kildall, up to the time when CP/M 2.2 was released in the late 1970s. Afterwards, CP/M was a major, if not dominant, operating system for microcomputers of the era. But for those who did not live in that era, the importance of CP/M is not at all clear, other than maybe its "influence" on MS-DOS for the IBM PC and for Microsoft.

But it's a matter of use and numbers to show that CP/M 1.4 and later CP/M 2.2 was a successful product for many years, and that Digital Research's subsequent products were successful into the 1980's.

A review of computer products of the late 1970's should show that many of them ran CP/M. The earliest portable computers - from Kaypro, Osborn - and desktop computers ran CP/M. When computers went from multiple cards to a single circuit board, most of them were Z80 based, and most of those ran CP/M.

Some idea of the economic value of these companies is available from a Web document by Roger Amidon, co-owner and developer at TDL (Trenton Design Labs) which produced S-100 systems and products in the 1970's. Their first product, the ZPU Z80 S-100 card, was said by Roger to sell "10,000 boards at $269 each, and then 50,000 at $189 each". Gross sales of $12 million in 1978-80 dollars, ain't small. His version of CP/M, called "TP/M", sold 100,000 units at $50 each across the TDL product line (20K units) and later the Epson QX-10 product line (75K units).

When Digital Research Inc. was sold to or merged with Novell Inc in 1991, the price was reportedly $136 million. Business references state that DRI had revenues of $40M just before the sale. This is hardly a failure by any reasonable standard. So how did DRI achieve that value?

1980's and the 8086

In the early 1980's, when the Intel 8086 and 8088 processors became available, many companies who made Z80-based systems created 8088-based systems. However, Digital Research did not provide a "CP/M-86" early on to accomodate these companies, despite requests by them to do so. So in some cases, those companies developed their own operating systems. One of them was Seattle Computer Products, and a programmer named Tim Paterson.

Seattle Computers, MS-DOS, and Microsoft

Mr. Paterson readily admits that he used the features of CP/M as a guide to develop his operating system for SCP, which at one point was called QDOS (for quick and dirty OS). In fact, the list of operating system functions - open and close files, read and write to them and so forth - duplicates the same list of functions for CP/M-80. To this day, many contend that Paterson "stole" QDOS from Digital Research in one way or another. I refuse to offer what would amount to a LEGAL opinion on what amounts to a legal issue of intellectual property and copyright. Why is this at all relevant today? Because of the IBM PC.

When the IBM PC was in secret development, IBM developers went to Bill Gates of Microsoft, to obtain their leading software product - Microsoft BASIC. They obtained a licence and rights to an 8086 version of that product. Then they went to Digital Research to obtain THEIR leading software product - an operating system derived from CP/M for the 8080. Now, there is controversy over what exactly occurred during those meetings. But the facts are, that IBM was not able to come to terms with DRI; IBM then turned to Microsoft; and Microsoft (Gates and Paul Allen) bought rights to the OS from Seattle Computer Products and created PC-DOS for IBM and MS-DOS for Microsoft. The success of MS-DOS, and Microsoft, followed from the introduction of the IBM PC in 1981.

However, despite suggestions otherwise, the success of the IBM PC was NOT the "failure" of CP/M or Digital Research. They did come up with CP/M-86, it was offered (at a price disadvantage) for the IBM-PC and for many other 8088 based microcomputers. For some time, the IBM PC competed not only with new 8088 microcomputers, but also with the "old" Z80 based systems which were faster, cheaper, and had more software available. However, the IBM PC had the money and computer market dominance of the IBM mainframe and minicomputer world - and therefore had entry into the "Fortune 500" companies (from the annual list by Fortune magazine, a major business publication, of the largest companies). In the era, it was said "nobody ever was fired for recommending IBM". The IBM PC prospered, and over a few years it became the dominant microcomputer of the early 1980's. However, with the advent of ever-cheaper manufacture of personal computers, and ever-faster improvement in speed and capacity, the CLONE market for IBM PC's became dominant over IBM own products. Later on, IBM lagged on development as well, and IBM lost leadership in sales and technology by the late 1980's, in the market they established.

DRI in the early IBM-PC era

Meanwhile, Digital Research produced a number of ever-more-sophisicated software products for both the 8080-based systems and for these new 8086-based systems. In the 8-bit world of the 8080 and Z80, they developed products like MP/M and CP/NET which were operating systems to accomodate additional RAM memory, and the beginnings of networked workstations. In the 16-bit world of the 8086, they offered CP/M-86 versions, MP/M as memory and network "hubs". The more powerful 8086 systems with more memory, faster processors could accomodate multiple users and run multiple programs, when DRI provided operating systems like Concurrent DOS. They also had more graphics hardware, and Digital Research's OS 's included GEM, a "windowing" product supporing multiple "screens" of one per program, because each program expected to use the whole screen for user display and entry.

Microsoft's MS-DOS did not have many of these features; while DRI's OS's incorporated most MS-DOS features and could run most MS-DOS programs. In fact, DRI's OS's were so much like Apple's Macintosh graphic interface, that Apple sued DRI and DRI was forced to remove or modify some features from its product. Microsoft developed a "Windows" operating system, but it took several years and three major versions before "Windows 3.1" was seen as a successful product over the "cash cow" which financed Windows development - namely MS-DOS, which ran to six major versions or more through the early 1990's.

Digital Research in the 1990's and beyond

My Web site does not describe Microsoft or MS-DOS, because that history is readily available. It does describe some of the post CP/M products of DRI in the 1970's and early 80's. Other Web sites have information on some of DRI's many OS and language products of the 1980' which I've only mentioned briefly here. As for the 1990's, I follow on my Web site how Digital Research was sold to Novell in 1991; then DRI assets were sold to Caldera, a computer company which later became SCO - the company which today claims ownership of Unix and has filed suits against some users of Linux. Finally, Caldera sold its DRI assets (including CP/M-80) to a holding company which today is called DR-DOS Inc.

DR-DOS Inc. still sells DR-DOS version 7 to companies which need an MS-DOS like operating system for products like disk backup software or hard-disk formatting software - programs which MUST run on their own operating system, typically from floppy disk. A verson of DR-DOS was put into "open source" by Caldera, and some variations of that code are available as open source today.

DR-DOS Inc has licensed personal use of CP/M-80 and CP/M-86 class products for individual use, through a private Web site operated by a person in Germany which is an "unofficial CP/M archive" of CP/M products and tools. Other CP/M archives are on the Web, copies of diskette archives of THOUSANDS of CP/M programs which were released to the public during the 1970's and 80's. In those days before the Web and even dial-up "bulletin board systems" of individual computers - another story itself - "freeware" and "shareware" software was distributed by stacks of disks bought from compaines or computer clubs run by hobbyists, businesspersons, anyone interested in using personal computers. These groups started as CP/M groups early on, IBM-PC groups later on. Also on the Web, are archives of commercial CP/M software, a good part of which has been released for free distribution by the original authors and developers - but some, called "abandonware", is neither officially released nor denied for release (unless yanked by request of the software owners).

Below are Web links to my site to specific discussions, or links to lists of links to other Web sites I've mentioned.

Web Links

This is my index Web page to my Digital Research Web site. Check there for other DRI pages and references to CP/M. To use CP/M today, check this "how-to" CP/M Web page of mine.

This pagelists some early Digital Research OS's after CP/M 2.2. That entire Web page describes early DRI products from CP/M-80 forward; a brief description of CP/M; some alternative OS's to CP/M; and information on running CP/M on today's computers or on computers of the 1970's. I also list the DRI manuals I have. Numerous Web links on that page lead to other sites with more information and software.

According to this report about Novell Inc., for for year 1991, "Acquisitions that year included Digital Research Inc. for $136 million....". Other sources refer to a stock swap of 3 million shares of Novell Inc. An interesting internal memo from Microsoft about the merger includes a press release which describes DRI as follows: "Digital Research, with 273 employees, had revenue of $40.9 million in its fiscal year ended Sept. 30 1990, up from $36.2 million in fiscal 1989. "

The "unofficial CP/M archive site" is maintained by Gaby Chaudry on her CP/M archive Web site pages.

John Elliott's extremely instructive CP/M technical home Web page. Several articles about CP/M in the modern context; a lot of technical information about CP/M 1.X, 2.X and 3.X as well as CP/M 86 versions; file formats; and many Web links. Updated sometime up to 2005.

P. Betti's mirror site or at katzy mirror site are mirrors of a repository site for "CP/M-86 for the IBM PC". This includes fixes needed to run CP/M-86 directly on "recent" Intel/Windows type systems today.

CP/M for the 8080 can be run on today's Windows-based computers using an "emulator". There are a number of emulators which were developed in the 1980's and 90's which run under MS-DOS. They can be run in most Windows systems in the "MS-DOS window". Or you can run Linux based, or Windows-based emulators. Check one of my DRI Web pages about some ways to run CP/M. That page also talks about running CP/M-86 on some modern Intel-based PC's.

For tools to read old CP/M diskettes: The Web page linked here discusses an MS-DOS based program called "anadisk" and "22disk" from Sydex.

This DRI page of 1990's products from DRI gives some year-by-year business history of Digital Research after it was bought by Novell Inc in 1991, through today when DRI assets are held and sold by DR-DOS Inc.

this site, by "Matthias" has a nice chart by year of DRI products.

My Web links for CP/M-supporting Web sites are: more DRI Web sites and S-100 related Web sites.

Contact information:

Herb Johnson
New Jersey, USA
To email @ me, see see my ordering Web page

Copyright © 2011 Herb Johnson