CP/M and Digital Research Inc. (DRI) Web pages

This document copyright Herbert R. Johnson, updated Dec 19 2022.

Contact and email information can be found in this notice.
To return to my S-100 Home page click here.
Also see my Morrow documentation. and Compupro documentation for related DRI manuals. My IMSAI Web page includes early work by Kildall.

Introduction to CP/M and Digital Research

Many software and hardware companies of the 1980's and beyond, began as one or two-person companies offering a CP/M-compatible program, or a 8080 or Z80-based hardware product or system. CP/M was the dominant operating system for the 8080 and Z80 based systems of the microcomputer market in the mid-1970's through well into the 1980's. Created by Dr. Gary Kildall before 1975 and sold quietly in that year as CP/M version 1.3 for $70 per disk, it became known as IMSAI's first diskette operating system IMDOS in 1976. Gary Kildall and his wife formed Digital Research Inc. to sell and support the product. A popular release was CP/M 1.4 in 1978, and later as CP/M 2.0 and 2.2 in 1979. It was popular because it was cheap and non-proprietary, and because it included all the software tools and information necessary to move it to any hardware platform with a terminal and a floppy diskette controller. Proprietary or competing Z80/8080 operating systems of the time were often program-compatible with CP/M. Non-Z80 systems sometimes had a "Z80 card" in order to run CP/M.

The Intel 8086 and 8088 processor, the latter used in the IBM PC, became available in the late 1970's. The origins of MS-DOS was an 8086-based OS written to be functionally and operationally compatible with CP/M 2.2 for the 8080. That OS was bought by Microsoft and sold to IBM as PC-DOS for their 1981 IBM PC. Throughout the 1980's, Digital Research produced CP/M-86 and a series of other operating systems for IBM-PC compatibles, as well as advanced OS's for 8080-based systems, and products for systems with 68000-compatible processors. Digital Research Inc. was bought by Novell in 1991 for $120 million. DRI OS products are still sold today (2008) by DRDOS Inc. Dr. Kildall died in 1994.

If you copy or link or reference any information on these pages or associated pages, please cite Herb Johnson as author and link to this Web page. We will keep this Web page link stable; links to other pages associated with this one may change over years. Updates to any information on these pages are welcome; we have many links to sites which may go "dark" so keep us posted! - Herb Johnson

Is CP/M forgotten? or still relevant?

With the 2004 publication of "They Made America", a popular biography of American achievers which contained a biography of Dr. Kildall, his achievements became more accessable to 21st century readers.

In 2009, a number of information technology (IT) and computing magazines developed themes around "the 25 anniversary of the Apple Macintosh", which first appeared in 1984. One other magazine which started in 1984 to cover the IBM PC, started their anniversary editorial with the following: "by 1984, PC's had started to gain traction among hobbyists and gamers, but the PC as a business tool was a novel concept." We told them: To the contrary, by 1984, CP/M systems had been sold for SEVERAL YEARS to business people; and provided a link to this page. We got a cursory "thank you" from the editor for our email.

Also since 2009, a number of "hobby groups" have developed their own CP/M capable hardware and are offering boards at cost. "Members" are developing hardware and software as freely available. Groups include N8VEM and s100computers.com and SEBHC. They mix old-school designs and modern hardware.

Meanwhile, more people in those groups and in others are discussing their revivals of CP/M and related hardware from 1970's and 80's system. I sponsor a few Web pages about some of those individuals, including myself.

And in 2014, the 40th anniversary of the first operation of CP/M, the IEEE will award Kildall's CP/M as a Milestone in Electrical Engineering and Computing.

- Herb Johnson

CP/M overview: Kildall and Digital Research

An outline of CP/M history

What began as my 2007 VCF EAST presentation on the early development of CP/M by Dr. Gary Kildall and his colleagues, has become a CP/M chronological history. This revised version is in outline form with links to JPEG images of original documents and publications. It led to the many pages referenced on this "home page".

Contents of my introductory DRI Web page are:

  • Editorial: What is CP/M? Where is it? How do I use it?
  • Digital Research and CP/M ownership: history and status today
  • CP/M products and the "unofficial CP/M web site"
  • early DRI OS's, brief descriptions
  • Sources of DRI manuals

    On A Web page about DRI later 16-bit products you'll find a history of DRI's 16-bit products and a history of ownership of DRI intellectual property. It also traces some derivative products like DR-DOS, FreeDOS, etc.

  • Digital Research corporate and product history
  • Corporate history of CP/M, 1999 to date
  • DRI descendent products (or not) today

    Here's many references to sources of DRI information: articles and publications, original documents.

    CP/M development

    See my page on early CP/M development for the following:

  • Summary of early CP/M and DRI history
  • Early DRI references in Dr. Dobbs Journal, BYTE
  • early DRI source code

    Look at this Web page on IMSAI "IMDOS" and CP/M

    IMSAI played an important role in DRI's product development.

    Dr. John Torode and Digital (Micro)Systems

    Dr. John Torode's hardware made Kildall's CP/M work on a floppy drive. He was first to sell a floppy controller with CP/M. See his history before and after Kildall, on this Web page; and see how that product was in a "race" with other floppy controllers on this Web page.

    Dr Torode's Digital Systems produced products for PC compatibles including HiNet local area networking; and a Z80 protable computer. The company was acquired by Apricot Computers in the late 80's.

    CP/M features, how-to

    See this document of features, programs, and methods of CP/M-80 version 2.2

    This should give you some idea about how CP/M-80 "worked", and how it was modified for use on other systems. To learn more about CP/M-80, look for other sites on the Web or old books about CP/M, or CP/M manuals scanned and put on the Web. Some Web link pages are mentioned below.

    This how-to Web page provides some ideas about how to get and "run" CP/M today, or past alternatives to CP/M. Contents include:

  • What is CP/M?
  • where can I get CP/M? what are the alternatives?
  • UNIX versus CP/M?
  • How do I run CP/M on my computer?
  • Some useful Web pointers

    A common question is "how do I run Internet, or TCP/IP, or "the Web", under CP/M?". It ain't that simple. Check this Web page for a march 2009 discussion and links to how it WAS, or may be, done.

    See how to read the CP/M version and serial numbers from various distributions of CP/M 1.4, 2.0, and 2.2. Courtesy of Jeff Shook.

    PL/M and derivatives

    Gary Kildall developed PL/M for the 8008 and 8080 for Intel, as an early high-level language for microprocessors. He and others subsequently developed versions of PL/M for other microprocessors. Here's some details about PL/M derivatives.

    Before and after CP/M

    What kind of "microcomputers" were around, in the days before and during CP/M?

    I can't follow all of them, but there were a handful of microprocessor manufacturers in the early days of 1975 and before. But on this Web page I link to discussions of some of those system and computers based on Intel processors.

    Gary Kildall worked for Intel and produced PL/M and other 8008 and 8080 tools.

    Kildall had an early start with the 8080 because he wrote Intel's cross-assemblers and simulators for the 8008. When he saw the 8080, he offered to Intel to write a "resident" PL/M for the 8080. They declined - and the resident operating system for his PL/M became CP/M.

    I discuss how Kildall became involved with BASIC on a Web page titled: BASIC, IMSAI and Digital Research.

    I discuss the dominance of CP/M on this Web page.

    That Web page shows the importance of CP/M and DRI in the 1970's and 80's, and how MSDOS came to be.

    TurboDOS was an alternative OS to CP/M in the 1980's.

    Discussions in the last several years have lead to a recent (2011) apparent release from copyright of TurboDOS. This Web page provides a little background, the notice of release, and Web links.

    See my page on post-1990 DRI history and products for the following:

  • Owners of DRI property in the 1990's: OpenDOS appears
  • The endless CP/M saga, 2002-2006
  • 2006: FreeDOS, OpenDOS and DRDOS 8 (RIP)
  • DRI descendent products (or not)
  • FreeDOS, OpenDOS
  • the status of REAL/32, a DRI descendent
  • the status of GEM, a DRI descendent

    Some other CP/M related Web pages on my site:

  • archive of Digital Research documents posted by E. Roche
  • S-100 and CP/M Web site pointers to software and discussions.
  • S-100 home page. Many early CP/M systems were S-100.

    Origins of this DRI history Web site

    Dr. Gary Kildall's operating system called CP/M is likely 35 years old as of 2009. That is based on a "fall of 1974" reference by Kildall to get Dr. John Torode to provide a working floppy controller to run his software on real hardware. During 1975 there were announcements and discussions of CP/M as a product in a new but popular computer magazine called "Dr. Dobb's Journal". Dr. Kildall and his company, Digital Research Inc., sold CP/M and subsequent operating systems and development tools into the 1990's, until the company was acquired by a series of other companies. As of 2006 the current owners of the DRI licenses including CP/M is DR-DOS Inc. Kildall died in 1994.

    My primary computing interests are in S-100 systems. Up until 2004, my Web site covered early Digital Research CP/M products, because S-100 systems used them. Then I had the following experiences, which I wrote about at the times they occurred.

    "There was a discussion in May 2004 in newsgroup comp.os.cpm, on realtime OS and CP/M computers. It happens that I have a collection of DRI documents and software which I've listed on my S-100 site. As that list and my site have been around for several years, this page is often found by Google searches on DRI. In the comp.os.cpm discussion, someone groused that a bit of my DRI info misled him. So I've added some researched OS descriptions to the page and asked the discussion for summary information or links to same." - end quote.

    Then, in 2006, I got mad about all the press that year for "the 25th anniversary of the IBM-PC" and "25 most important personal computers", "computer software", etc. etc. - all of which considered the IBM PC and MS-DOS as much more important that those computers and software before 1981. Hrummph! So I gathered some more information...

    I've added more than a bit to that page since then. I previously described the early development history of CP/M as products (since 1975) on that page. In Feb 2007 I spun it off to it's own Web page.. I also spun off the history of DR-DOS in the 1990's and later to another Web page.

    In 2007 I gave a talk at the Vintage Computer Festival - East V4.0 on "30 years of CP/M". My outline and images shown at that talk are on this Web page. A talk to a college class on computer restoration, led to this page on why CP/M and DRI are important as a dominant OS provider in the 70's and how CP/M and MS-DOS are related.

    Now my domain Web site has a whole section for DRI and early CP/M developments. This page is an index to all those other pages. My former primary DRI page now lists the earliest DRI OS products through CP/M 2.2. The critical work and support from Kildall's colleague, Dr. John Torode of Digital Systems, is discussed and explored. Also there are notes about a few operating systems derived from and compatible with DRI products, commericial and "free", and describes their current status. We have some original documents and disks for early DRI products, which are listed there and available.

    In 2008, we expanded discussions about items related to CP/M and Kildall's work. We've included his Intel products such as PL/M; Intel's development systems and their ISIS; discussions of other floppy-drive-based operating systems in CP/M early days. In 2009, we revised our early history of CP/M slightly as discussions with others, and the uncovered history of these other developments, clarified the sequence of events. We've had more time to organize our pages including this one; and to break up larger pages into smaller ones.

    Since 2008, I've added information about Digital Research from Kildall, and Digital Systems from Torode. People send me contributions, including notes about their work in these companies.

    Contact information:

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

    Copyright © 2022 Herb Johnson