Gary Kildall

Published Oct 31, 2023
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Gary Kildall, image: Nephilim Corporation

Image from Nephilim Corporation.

Gary Kildall (1942 - 1994) was an American computer scientist, entrepreneur, and technology educator. Among his contributions, he is best known for the development of PL/M, the first high-level programming language for microprocessors, and CP/M, an industry-standard operating system for early personal computers.


Kildall earned a B.A., M.S., and Ph.D. in computer science at the University of Washington. Kildall’s Ph.D. thesis founded data-flow analysis, an approach to using compilers to optimize code.

Technical Innovations

  • PL/M: A high-level programming language for microprocessors. Kildall developed PL/M for Intel in 1973 and it was used in Intel microprocessors throughout the ‘70s and ‘80s. PL/M is widely recognized as the first high-level programming language and compiler for microprocessors.
  • CP/M: An operating system for microprocessors. The invention of CP/M enabled microprocessors to communicate with disk drives, a necessity for the invention of personal computers. CP/M sold over 250,000 copies and anticipated much of the later functionality of MS-DOS, the precursor to Microsoft Windows.
  • BIOS: The Basic Input/Output System, a routine used to initialize the hardware and operating system on a microprocessor. Kildall developed BIOS to enable CP/M to be installed on different hardware without being modified.
  • XLT86: A compiler that translates source code written for the Intel 8080 microprocessor into source code for the Intel 8086 microprocessor (a source-to-source compiler or transcompiler). XLT86, released in 1982, was one of the first transcompilers to implement code optimization techniques, which were themselves pioneered by Kildall in his Ph.D. thesis.
  • KnowledgeDisc: A CD-ROM containing the entirety of Grolier’s Academic Encyclopedia. Kildall helped develop the file system and data structures for this product, which was released in 1985 as the first commercially-available CD-ROM product. Kildall presented the KnowledgeDisc at a keynote talk at the first annual Microsoft CD-ROM Conference.

Business Ventures

  • Digital Research, Inc. (DRI): A company founded by Kildall to sell operating system software including CP/M and its successors. DRI was sold in 1991 for 80-million USD.
  • Activenture: A spin-off company from DRI focusing on optical disc technology, such as the CD-ROM. Kildall released the KnowledgeDisc through Activenture.

Technology Education

  • After his Ph.D., Kildall taught computer science for several years at the Naval Postgraduate School in Monterey, California.
  • From 1983 to 1990, Kildall was a co-host of the PBS show Computer Connections, which documented developments in the growing personal computer industry.

Personal Writings

In his last years, Kildall worked on a memoir, titled Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry. The first several chapters of this manuscript are available for free.

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