Dennis Ritchie

His father, Alistair Ritchie, worked at Bell Labs and co-wrote The Design of Switching Circuits, a standard text on how telephone equipment makes decisions. The son grew up in Summit, New Jersey, took Harvard degrees in physics and applied mathematics in 1963, and in 1967 walked into the Bell Labs Computing Science Research Center, where he stayed for the rest of his working life. In 1968 he completed a draft doctoral thesis on computational complexity and program structure under Patrick Fischer, and never officially received the degree. The thesis then went missing. In 2020 the Computer History Museum recovered a copy by working through both families.

Bell Labs pulled out of the Multics operating system. Ken Thompson found a discarded PDP-7 and wrote his own system on it, with Ritchie and others helping, and in 1970 Brian Kernighan proposed calling it Unix, at the older project's expense. Thompson wrote a language called B. Ritchie replaced it with C, which sits close enough to the hardware to build an operating system in and far enough from it to move that system to a different machine. Then they used C to write Unix, and the two stopped being separable. In 1978 Ritchie and Kernighan published The C Programming Language, known ever since by their initials. In the same decade he worked out an attack on the M-209 cipher machine with James Reeds and Robert Morris.

The M-209 attack could break messages of 2,000 to 2,500 letters. After talking to the National Security Agency, who said foreign governments were still using such machines, the three authors decided not to publish. That is the only time his work was held back, and he held it back himself. Everything else went everywhere and carried his name nowhere. C is the ancestor of C++, Objective-C, C# and Java. Linux and the BSD systems grew out of Unix, and Ritchie called the Linux phenomenon delightful, treating it as a continuation of what he and Thompson had begun rather than as a theft. Doug McIlroy summed up their years at the Labs by writing that anything not otherwise attributed could safely be assumed to be theirs.

He was found dead at his house in Berkeley Heights, New Jersey on October 12, 2011, at 70. He had lived alone and had been in poor health for years after treatment for prostate cancer and heart disease, and the date is recorded with a qualifier because nobody was there. Steve Jobs had died a week earlier and the obituary pages were full. The releases that followed were dedicated to him instead — Fedora 16 a month later, FreeBSD 9.0 in January 2012 — and an asteroid carries his name. Paul Ceruzzi wrote the line that stuck: if you had a microscope and could look inside a computer, you would see his work everywhere in there.

Dennis Ritchie's life against the full span of the corpus.

• Unix invention
  Begun by Ken Thompson on a discarded PDP-7, with Ritchie and others 1969
• The C programming language invention
  Low enough to write an operating system in, portable enough to move it 1972
• The UNIX Time-Sharing System article
  Written with Thompson. The paper that told the outside world what they had. 1974
• The C Programming Language book
  Written with Brian Kernighan and known ever after as K and R 1978
• Plan 9 from Bell Labs invention
  The successor operating system he worked on after Unix 1992

• 1963 aged ~22 Graduates from Harvard in physics and applied mathematics
• 1967 aged ~26 Joins the Bell Labs Computing Science Research Center His father had spent his career at the same company.
• 1968 aged ~27 Completes a doctoral thesis he never formally receives a degree for The Computer History Museum found a copy of it in 2020.
• 1969 aged ~28 Helps Ken Thompson build an operating system on a cast-off PDP-7
• 1970 aged ~29 Brian Kernighan suggests calling it Unix The name is a joke at the expense of Multics.
• 1972 aged ~31 Creates C to replace Thompson's language B
• 1978 aged ~37 Publishes The C Programming Language with Kernighan
• April 21, 1999 aged 57 Receives the National Medal of Technology from Bill Clinton with Thompson
• October 12, 2011 aged 70 Found dead at his home in Berkeley Heights at 70 He had received the Japan Prize with Thompson earlier that year.

• Ken Thompson b. 1943
  Co-created Unix at Bell Labs and later co-designed the Go programming language. co-created Unix with
• Claude Shannon 1916–2001
  Mathematician and engineer who founded information theory, the basis of all digital communication. the Bell Labs precedent
• Grace Hopper 1906–1992
  Computer scientist and Navy rear admiral who helped develop early programming languages and computing. the earlier language designer
• John von Neumann 1903–1957
  Hungarian-American mathematician and engineer whose computer architecture remains the basis of modern computing. built the machine his work assumed
• Steve Jobs 1955–2011
  Co-founder of Apple who revolutionized personal computing, music, and mobile communications. died a week before him