Gary Kildall

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Gary Arlen Kildall (born May 19, 1942 in Seattle , † July 11, 1994 in Monterey , California ) was an American computer scientist. He is known as the inventor of the CP / M operating system and founder of Digital Research .


In 1963, Gary Kildall married his high school sweetheart Dorothy McEwen (1943-2005). Their son Scott was born in 1969 and their daughter Kristin in 1971. After receiving his doctorate in computer science from the University of Washington in 1972, he first came into contact with the burgeoning microcomputer age that same year while working as a computer science teacher at the Naval Postgraduate School (NPS) in Monterey. During this time he also developed the basics of data flow analysis .

1973 Kildall began programming a runtime environment for the programming language PL / I (Programming Language One). In the early 1970s was the invention of the floppy disk (Engl. Floppy disk ), a new, low-cost storage medium for minicomputers. In order to be able to operate it on microcomputers, however, a suitable operating system was required , which Kildall completed in 1974. He called it CP / M ("Control Program / Monitor", later mostly reinterpreted as "Control Program for Microcomputers"), which he completed in 1975 in version 1.0. Initially, Kildall offered Intel CP / M for $ 20,000 because he had previously worked as a freelance consultant on various projects for Intel. When Intel declined, he founded Digital Research (DRI) in late 1975 .

After leaving the NPS in 1976, he continued his work on CP / M, which he originally obtained through classified ads in computer magazines such as Dr. Dobb's Journal , later also advertised and sold in the Byte . With the MITS Altair 8800 , a computer was finally presented in 1975 on which the CP / M could run. In 1976 IMSAI approached Gary Kildall and asked for a version of CP / M adapted to the IMSAI 8080 (a clone of Altair). CP / M already existed in version 1.2, and so Kildall had the idea of dividing his operating system into a hardware-specific part called BIOS and a hardware-independent part called BDOS. Clones of this computer that had a floppy disk drive and required CP / M as the operating system came onto the market at the end of the year, and by 1977 it was the most popular and widely used operating system in the world. CP / M ran on virtually any computer with an 8080 , 8085 , or Z80 processor.

In 1977, Kildall licensed CP / M to IMSAI for $ 25,000, laying the foundation for DRI's steep economic rise.

In 1981 DRI had 75 employees and annual sales of six million dollars. In the same year, IBM announced its plans for the IBM personal computer . In 1980, IBM turned to Digital Research in search of an operating system for the IBM PC, which was under development. Allegedly, Bill Gates personally referred IBM to DRI. Microsoft had sold a plug-in card for the Apple II with which the CP / M-80 could also be used on this computer. The card sold so well that Microsoft sold almost as many CP / M licenses in a bundle as DRI itself. For this reason, IBM is alleged to have initially mistakenly asked Microsoft about the delivery of an operating system. As an established system with 200,000 installations, CP / M was probably the first choice for the future operating system of the new IBM PC, but Digital Research finally lost with its CP / M to Microsoft's MS-DOS . To this day, the reasons why no contract was concluded between Digital Research and IBM are the subject of speculation.

Rumor has it that IBM representatives did not meet Gary Kildall when they asked him to offer the operating system. According to this, Gary Kildall should have preferred to go gliding. However, this version is controversial, because in certain circles it was well known that Gary Kildall actually left business matters to his wife Dorothy. And so another rumor says that she was simply not ready to sign a confidentiality agreement, as the IBM representatives had asked her to do. Tom Rolander, then an employee at Digital Research, however, testified that Gary Kildall flew with him to a meeting with NorthStar Computers that morning, came back after lunch and signed the confidentiality agreement. According to his account, a deal was not reached with IBM because both the payment was too low (100,000 USD for the exclusive right to sell the CP / M-86 without volume restrictions) and the request to rename the operating system to PC-DOS was not acceptable. If Gary Kildall had agreed to this, he would have had to grant this right to all customers.

These are said to have returned to Bill Gates. Gates offered IBM to supply an operating system. He got it from a small company called Seattle Computer Products . It was a CP / M clone for the 8086 CPU called 86-DOS . It was programmed by Tim Paterson . He had orientated himself closely to the properties and operating system interfaces of CP / M. Microsoft initially licensed 86-DOS and bought the rights to it in late July 1981. Version 1.0 of the PC DOS operating system that was delivered later was a version of 86-DOS that was adapted to the IBM PC. When Gary Kildall found out about the similarity of the two operating systems while they were still in development, he wrote to IBM and Bill Gates asking for clarification. It was only then that IBM learned how PC-DOS came about. DRI received $ 800,000 for not suing IBM, and IBM agreed to offer CP / M-86 for the IBM PC as well and pay license fees. However, it was offered at six times the price of PC-DOS, which is why PC-DOS very soon became dominant.

In 1983, Gary Kildall developed GEM, the Graphical Environment Manager , a graphical operating system interface, which Kildall was inspired to develop by working with Apple's Lisa and which was licensed by Atari in 1984 for its ST computers. GEM was available earlier than Microsoft Windows and had much lower hardware requirements. But Kildall did not recognize the potential that GEM had, and so it was hardly actively marketed and soon overtaken by the products of Apple and Microsoft. Unlike Microsoft, Apple even sued DRI because of its similarity to the Mac OS, which is why it had to be adapted. In fact, DRI came under increasing pressure due to the success of Microsoft's MS-DOS, and there was a crisis within the company, not least because Kildall and his wife had split up in 1983 (and later divorced), but both stayed with the company.

In May 1988, Digital Research brought an MS-DOS -compatible operating system to the market with DR-DOS , since the multitasking concurrent CP / M-86 , which was brought onto the market in 1984, did not conflict with the dominant position of MS DOS was able to prevail. He also developed the data format for the multimedia CD and launched "Grolier's Encyclopedia" on CD-ROM, a lexicon that was one of the first products to use hypertext for navigation.

In 1991, Kildall sold Digital Research to Novell and moved to West Lake Hills , a suburb of Austin , Texas . Here he founded the company Prometheus Light and Sound and got involved with AIDS- infected children and young people.

Although the sale of Digital Research to Novell had made him a very wealthy man, it brought little luck to Gary Kildall in his private life. Friends reported that the fact that people like Bill Gates and Steve Jobs were hailed as pioneers in the face of the rise of the personal computer while it (like others) was being forgotten deeply offended him - although he never made this public. In addition, his second marriage also broke up.

Whether PC DOS violated the copyrights of CP / M is still the subject of speculation. There are rumors of threatened lawsuits and secret deals, but neither side has ever spoken publicly about them. Shortly before his death, Kildall wrote his 226-page memoir, which allegedly also included an account with Microsoft, but they have not yet been published. However, they served as a template for a chapter on Gary Kildall in a 2004 book by Harold Evans : They Made America . For the last few years of his life, Gary Kildall worked extensively on a manuscript for a book: Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry .

Kildall firmly believed that PC DOS was infringing its copyrights on CP / M. But the jurisprudence regarding computer software was still in its infancy back then. The historic decision in the Apple against Franklin case , which first confirmed the applicability of copyright to software in the USA, was only two years ago and, according to employees and friends, Kildall did not want to get involved in a lengthy and costly legal battle with IBM. Many years later, in several interviews, Gary Kildall is reported to have said: “Ask Bill [Gates] why the string in function 9 ends with a dollar sign. He can't answer. Only I know. ”Former associates of his, like Gordon Eubanks, portrayed him as someone who avoided conflict. He believed that the better system would prevail on the market, and for a long time DRI didn't offer programming languages ​​because he didn't want to provoke Bill Gates.

Gary Kildall died on July 11, 1994 at the age of 52 of internal bleeding from a head injury sustained on July 8, 1994 in Monterey, California.


  • Bernd Leitenberger: Computer history (s) The first years of the PC. BOD, Norderstedt 2012, ISBN 978-3-8423-5164-6 , pp. 86-105

Web links

Individual evidence

  1. A unified approach to global program optimization | Proceedings of the 1st annual ACM SIGACT-SIGPLAN symposium on Principles of programming languages. Retrieved June 25, 2020 .
  2. a b Bernd Leitenberger: Computergeschichte (n) pp. 96–99
  3. Bernd Leitenberger: Computergeschichte (n) pp. 101-101
  4. Bernd Leitenberger: Computergeschichte (n) P. 102 ff