Fifty Years of the Personal Computer Operating System

Fifty Years of the Personal Computer Operating System
=====================================================
By David Laws, April 18, 2024

PC software pioneer Gary Kildall demonstrated CP/M, the first
commercially successful personal computer operating system in Pacific
Grove, California, in 1974. Following is the story of how his
company, Digital Research Inc., established CP/M as an industry
standard and its subsequent loss to a version from Microsoft that
copied the look and feel of the DRI software.

Early Days
==========
Gary Arlen Kildall was born to a family of Scandinavian descent in
Seattle, Washington, in 1942. His inventive skills flourished in
repairing automobiles and having fun but suffered in scholastic
pursuits. He qualified for admission to the University of Washington
based on his teaching experience at the family-owned Kildall Nautical
School rather than his high school grades.

Dorothy and Gary, circa 1978. Photo: Courtesy Kildall Family
<https://computerhistory.org/wp-content/uploads/2016/08/
gary-kildall-gary-dorothy-1978.jpg>

Gary entered college and married his high school sweetheart Dorothy
McEwen in 1963. He was one of 20 students accepted into the
university's first master's program in computer science. Here, his
mathematical talents were applied to a subject that fascinated him:
all-night sessions programming a new Burroughs computer. To avoid the
uncertainty of the draft at the height of the Vietnam War, on
graduating with a PhD, he entered a US Navy officer training school
and was posted to serve as an instructor in computer science at the
Naval Postgraduate School (NPS) in Monterey, California.

Herrmann Hall, Naval Postgraduate School, Monterey. Creative Commons
CC0 1.0 Universal Public Domain Dedication.
<https://computerhistory.org/wp-content/uploads/2024/04/
Herrmann-Hall-Naval-Post-Graduate-School.jpg>

Gary remained at NPS as an associate professor after his tour of duty
ended in 1972. He became fascinated with Intel Corporation's first
microprocessor chip and simulated its operation on the school's IBM
mainframe computer. This work earned him a consulting relationship
with the company to develop PL/M, a high-level programming language
that played a significant role in establishing Intel as the dominant
supplier of chips for personal computers.

To design software tools for Intel's second-generation processor, he
needed to connect to a new 8" floppy disk-drive storage unit from
Memorex. He wrote code for the necessary interface software that he
called CP/M (Control Program for Microcomputers) in a few weeks, but
his efforts to build the electronic hardware required to transfer the
data failed. The project languished for a year. Frustrated, he called
electronic engineer John Torode, a college friend then teaching at UC
Berkeley, who crafted a "beautiful rat's nest of wirewraps, boards
and cables" for the task.

This is going to be a "big thing"
=================================
Late one afternoon in the fall of 1974, together with John Torode, in
the backyard workshop of his home at 781 Bayview Avenue, Pacific
Grove, Gary "loaded my CP/M program from paper tape to the diskette
and 'booted' CP/M from the diskette, and up came the prompt: *."

"This may have been one of the most exciting days of my life, except,
of course, when I visited Niagara Falls," he exclaimed. We now have
the power of an IBM S/370 [mainframe computer] at our fingertips."
This is going to be a "big thing," they told each other and "retired
for the evening to take on the simpler task of emptying a jug of
not-so-good red wine ... and speculating on the future of our new
software tool."

By successfully booting a computer from a floppy disk drive, they had
given birth to an operating system that, together with the
microprocessor and the disk drive, would provide one of the key
building blocks of the personal computer revolution. While they knew
it was important, neither realized the extraordinary impact it would
have on their lives and times.

781 Bayview Avenue, Pacific Grove, circa 1974. Photo: Courtesy
Kildall Family
<https://computerhistory.org/wp-content/uploads/2024/04/
Kildall-home.jpg>

As Intel expressed no interest in CP/M, Gary was free to exploit the
program on his own and sold the first license in 1975. He continued
teaching part-time at NPS, and in 1976, with his wife Dorothy as
cofounder, they established Intergalactic Digital Research to pursue
commercial opportunities. They shortened the company name to Digital
Research Inc. (DRI) when it became available.

Glenn Ewing, a former NPS student, approached DRI with the
opportunity to license CP/M for a new family of disk subsystems for
fast-growing microcomputer maker IMSAI Inc. Reluctant to adapt the
code for another controller, Gary worked with Glen Ewing to split out
the hardware dependent-portions so they could be incorporated into a
separate piece of code called the BIOS (Basic Input Output System).

Before CP/M, computer manufacturers designed their operating systems
to work only with their own hardware and peripheral equipment. An IBM
OS would only work with IBM computers; a Burroughs OS would only work
with Burroughs computers, etc. Applications had to be written for
each computer's specific OS. Such "closed systems" made it difficult
or impossible to mix and match the best pieces of equipment and
software applications programs from different manufacturers.

The BIOS code allowed all Intel and compatible microprocessor-based
computers from other manufacturers to run CP/M on any new hardware.
This capability stimulated the rise of an independent software
industry by expanding the market's potential size for each product. A
single program could run without modification on computers supplied
by multiple manufacturers, laying an essential foundation for the
personal computer revolution.

DRI advertisement from 1978
<https://computerhistory.org/wp-content/uploads/2024/04/
DRI-ad-1978.png>

Dorothy and Gary opened their first office at 716 Lighthouse Avenue,
Pacific Grove, on the upper floor, with a view of Monterey Bay. They
sold CP/M disks via mail order and walked to the post office every
workday to pick up checks resulting from ads placed in industry
magazines such as Byte and Dr. Dobbs' Journal of Computer
Calisthenics and Orthodontia.

A licensing deal with computer manufacturer IMSAI bestowed
credibility across the industry. CP/M became accepted as a standard
and was offered by most early personal computer vendors, including
pioneers Altair, Amstrad, Kaypro, and Osborne.

Outside the DRI office at 801 Lighthouse Avenue in November 1980.
Photo: John Pierce
<https://computerhistory.org/wp-content/uploads/2024/04/
DRI-office-1980-861x1024.jpg>

In 1978, revenue topped $100,00 per month, and DRI purchased a
Victorian house at 801 Lighthouse Avenue for the company
headquarters. By 1980, DRI employed more than 20 people, and Fortune
magazine reported that the company generated revenue of $3.5 million,
five times the revenue of Microsoft at that time. Gary also acquired
a Piper aircraft that allowed him to fly from Monterey to meet
regularly with his customers in Silicon Valley and beyond.

To accommodate the expanding engineering staff hired to service the
hundreds of different computer models used by more than a million
people worldwide, DRI purchased a 1909 American Foursquare-style
residence at 734 Lighthouse. Today, it houses the offices of the
Carmel Pine Cone newspaper.

Gary in 734 Lighthouse Avenue. Photo: John Pierce
<https://computerhistory.org/wp-content/uploads/2024/04/
Gary-Kildall-Lighthouse-Ave.jpg>

One Friday afternoon, Gary called the engineering staff together and
announced that he would give them all a raise over the weekend. On
Monday, when they returned to work, contractors began raising the
building to make room in the basement for a new Digital Equipment
Corporation VAX 11/750 computer system. After several weeks,
supported by heavy wooden beams and house jacks, the engineers' desks
were five feet higher.

By 1983, DRI's annual sales reached $45 million. The company employed
over 500 people, including more than 100 engineers, and had expanded
into another building at 160 Central Avenue, which today houses the
Monterey Bay Aquarium's offices.

The IBM PC Effect
=================
In 1980, IBM established a new business division in Boca Raton,
Florida, to develop a desktop computer for the mass market. To get
the IBM PC, as it became known, to market as quickly as possible,
they used commercially available components, including an Intel
microprocessor chip. Bill Gates knew Gary from early discussions
about merging their companies and setting up shop in Pacific Grove,
so when an IBM procurement team visited Microsoft to license the
BASIC interpreter program, he referred them to DRI for an operating
system.

Gary at Monterey Airport with his Piper Aerostar.
Photo: Tom Rolander
<https://computerhistory.org/wp-content/uploads/2024/04/
Gary-Kildall-Monterey-airport-1024x703.jpg>

When the IBM team arrived in Pacific Grove, they met in the morning
with Dorothy and DRI attorney Gerry Davis to agree on the terms of a
non-disclosure agreement. Gary, who had flown his aircraft to Oakland
to meet an important customer, returned in the afternoon, as
scheduled, to discuss technical matters. IBM wished to purchase CP/M
outright, whereas DRI sought a per-copy royalty payment in order to
protect its existing base of business. The meeting ended in an
impasse over financial terms, but Gary believed they had essentially
agreed to do business.

Kildall tried to renew the negotiations a couple of weeks later. IBM
did not respond because, in the meantime, Bill Gates purchased an OS
from Seattle Computer Products that was written to emulate the look
and feel of CP/M. He then sold a one-time, non-exclusive license to
IBM, which used the designation PC DOS. With great foresight, he
retained the right to license the product to others as MS-DOS.

When Gary learned of this transaction, he threatened IBM with a
lawsuit over what he believed was an illegal copy of CP/M. IBM
responded by agreeing to fund DRI to adapt CP/M for the PC and to
make both brands of OS available to customers. With CP/M's reputation
and enhanced features, DRI believed customers would opt for the
better product.

IBM announced the PC on August 12, 1981, but with the PC-DOS list
price set at $40 versus $240 for CP/M, most customers simply chose
the former as the lower-cost option. Attorney Gerry Davis recalled
that "IBM clearly betrayed the impression they gave Gary and me."

Aftermath
=========
DRI continued to thrive for several years with a multi-tasking
operating system for the IBM PC-XT and a host of new products. The
company also introduced operating systems with windowing capability
and menu-driven user interfaces years before Apple and Microsoft.

At its peak, DRI employed over 500 people and opened operations in
Asia and Europe. However, by the mid-1980s, in the struggle with the
juggernaut created by the combined efforts of IBM and Microsoft, DRI
had lost the basis of its operating systems business.

Dispirited, Gary, who never relished the responsibility of managing a
large company or displayed the cut-throat business acumen of a Gates,
sold the company to Novell Inc. of Provo, Utah, in 1991. Ultimately,
Novell closed the California operation and, in 1996, disposed of the
assets to Caldera, Inc., which used DRI intellectual property assets
to prevail in a lawsuit against Microsoft.

In other pursuits, Gary founded KnowledgeSet with his friend and DRI
VP of engineering, Tom Rolander, where they created the first CD-ROM
encyclopedia for Grolier.

In an oral history for the Computer History Museum, Brian Halla,
Intel's technical liaison to DRI, recalls that Gary "showed me this
VAX 11/780 that he had running in his basement, and he was so proud
of it, and he said, 'I figured out a way to have a computer generate
animation,' and he said, 'Watch this. And he runs a demo of a Coke
bottle that starts real slowly and starts spinning, and so as maybe
several months went by, he lost interest in this, and he sold his
setup to a little company called Pixar.'"

Kildall continued to innovate after selling DRI. He moved to Austin,
Texas, where he founded Prometheus Light and Sound to explore
wireless home networking technology and participated in charitable
work for pediatric AIDS.

Gary Kildall died in 1996 at age 52 following an accident in
Monterey. His ashes are buried in Seattle, the hometown he shared
with Bill Gates. Dorothy McEwan Kildall purchased the Holman Ranch in
Carmel Valley and served on many community boards, including the
Heritage Society of Pacific Grove. She died in 2005.

The Legacy of Gary Kildall
==========================
In 1995, the Software and Information Industry Association presented
Gary Kildall with a posthumous Lifetime Achievement Award, citing
eight significant areas in which he contributed to the microcomputer
industry.

In an obituary published in the Microprocessor Report in 1994, his
friend, the late John Wharton, commented, "I don't think Gary ever
really begrudged Bill Gates his business success or his personal
fortune. ... what I think Gary wanted most was to share his
excitement and enthusiasm for computers and technology with others."

Gary Kildall in 1988 Photo: Copyright Tom O'Neal, Carmel Valley, CA
<https://computerhistory.org/wp-content/uploads/2019/07/
gary-kildall-729x1024.jpg>

On April 25, 2014, the Institute of Electrical and Electronic
Engineering, "The world's largest professional association for the
advancement of technology," installed a bronze IEEE Milestone in
Electrical Engineering and Computing plaque outside the former DRI
headquarters at 801 Lighthouse Avenue. The Milestone program honors
important events in electrical engineering and computing.
Achievements such as Thomas Edison's electric light bulb, Marconi's
wireless communications, and Bell Labs' first transistor are
recognized with plaques in appropriate locations.

<https://ethw.org/Milestones:
The_CP/M_Microcomputer_Operating_System,_1974>

<https://computerhistory.org/wp-content/uploads/2024/04/
IEEE-CPM-plaque-1024x682.jpg>

The citation reads: "Dr. Gary A. Kildall demonstrated the first
working prototype of CP/M (Control Program for Microcomputers) in
Pacific Grove in 1974. Together with his invention of the BIOS (Basic
Input Output System), Kildall's operating system allowed a
microprocessor-based computer to communicate with a disk drive
storage unit and provided an important foundation for the personal
computer revolution."

In 2017, US Navy dignitaries, friends, family, and peers gathered to
celebrate the dedication of the Gary A. Kildall Conference Room on
the Naval Postgraduate School campus in Monterey. The ceremony
included the installation of a duplicate of the IEEE plaque in the
conference room.

Despite this wide recognition of his technical accomplishments,
Gary's legacy remains mired in a tangle of myths and conspiracy
theories. The most persistent being driven by a 1982 comment
attributed to Bill Gates and published in the London Times newspaper
that "Gary was out flying when IBM came to visit, and that's why they
did not get the contract."

The former editor of the Times, Harold Evans, atoned for that story
in a PBS documentary and his book They Made America: Two Centuries of
Innovators from the Steam Engine to the Search Engine. The subtitle
of the chapter on Gary, "He saw the future and made it work. He was
the true founder of the personal computer revolution and the father
of PC software," offers a sympathetic telling of the life and times
of the entrepreneurial genius who helped give birth to the PC
operating system 50 years ago this year.

Additional information at the Computer History Museum
=====================================================
Comments in quotes in this article without source attribution are
from Gary's unpublished draft of Computer Connections: People,
Places, and Events in the Evolution of the Personal Computer
Industry, written in 1993. The Kidall family has authorized the
online publication of extracts from this memoir in the blog
Gary Kidall: In His Own Words.

<https://computerhistory.org/blog/in-his-own-words-gary-kildall/>

The Computer History Museum has also made the source code of several
early releases of CP/M available for non-commercial use.

<https://computerhistory.org/blog/
early-digital-research-cpm-source-code/>

A search for "Kildall" in the CHM collection catalog yields 45
records comprising objects, documents, and images, including a video
of the 2014 CP/M IEEE Milestone Dedication event.

<https://www.computerhistory.org/collections/search/?s=kildall>

<https://www.youtube.com/watch?v=HO6IPpL0y8g&t=151s>

From: <https://computerhistory.org/blog/
fifty-years-of-the-personal-computer-operating-system/>