Dennis Ritchie

Dennis MacAlistair Ritchie (1941-2011) designed the C programming language and, with Ken Thompson, co-created UNIX. He spent his entire working life at Bell Labs and shunned the spotlight, but the two artefacts he left behind — C and UNIX — still run, directly or by descent, inside very nearly every operating system, language runtime, network appliance and embedded device on Earth.

Background

Ritchie was born on 9 September 1941 in Bronxville, New York. His father, Alistair Ritchie, was a long-serving switching engineer at Bell Labs and a co-author of the standard textbook The Design of Switching Circuits (1951). The influence ran deep: Dennis would eventually seek a career at the same laboratory.

He studied physics at Harvard, earning a bachelor's degree in 1963 and submitting a doctoral thesis in applied mathematics on subrecursive hierarchies in 1968. The doctorate was never formally awarded — by his own account he forgot to pay the modest binding fee required to deposit a bound copy of the thesis with the university. The story has become a favourite illustration of his slight, almost airy vanity.

In 1967 Ritchie joined the Computing Sciences Research Center at Bell Labs, in Building 1127, Murray Hill. He stayed there for the next forty-four years without once changing employers.

Major Contributions

UNIX (1969-)

In 1969, just after Bell pulled out of the MIT-GE-Bell joint Multics project, Ken Thompson began prototyping a small, congenial time-sharing system on a disused DEC PDP-7. That prototype became UNIX. Ritchie joined the effort early, leading work on the filesystem, the device-driver layer and, crucially, the later rewriting of the whole kernel in C.

The UNIX design philosophy — small tools combined through pipes, everything is a file, text is the universal interface — was hammered out by Ritchie, Thompson, Brian Kernighan, Doug McIlroy and the rest of the tiny Building 1127 team. There was no ARPA or AT&T mandate driving the work; it was undertaken on internal research time, which is part of the legend.

The C Language (1972-)

The earliest UNIX was written in assembler, but between 1971 and 1973 Ritchie evolved Thompson's B language into something quite new: C, with structures, a type system and a regularised treatment of pointers. In 1973 the UNIX kernel itself was rewritten in C — the first sustained demonstration that a portable operating system, with performance close to machine code, was actually feasible.

In 1978 Ritchie and Brian Kernighan published The C Programming Language (universally known as K&R). The canonical "hello, world" first appeared in print in that book. K&R set the standard, in concision and density, for every programming-language primer that followed.

C was standardised by ANSI in 1989 (C89) and by ISO in 1990. Since then it has formed the substrate of the Linux kernel, the Windows NT kernel, the lower layers of macOS, almost every embedded system, and the interpreters for Python, Ruby and many others. The vast majority of the world's foundational software is written in C.

Plan 9 and Inferno

In the late 1980s Ritchie, Thompson, Rob Pike and others began work on Plan 9 from Bell Labs, a distributed operating system intended as UNIX's successor. Plan 9 was never a commercial success, but it introduced UTF-8, generalised the /proc filesystem and seeded design ideas that resurfaced in the Go language. In the 1990s Ritchie also led work on Inferno, a Plan 9 derivative.

Awards and Honours

• 1983 — ACM Turing Award, jointly with Ken Thompson, "for the development of generic operating systems theory and specifically for the implementation of the UNIX operating system."
• 1990 — IEEE Richard W. Hamming Medal.
• 1999 — US National Medal of Technology, presented by President Clinton.
• 2011 — Japan Prize for Information and Communications, jointly with Ken Thompson.

Legacy

Ritchie never married. He died at his home in Berkeley Heights, New Jersey, on or about 12 October 2011, aged 70. He had long been in poor health with heart disease and prostate cancer; living alone, he was found some days after his death, and the precise date is an estimate.

His passing was largely overshadowed by the wave of tributes for Steve Jobs, who had died a week earlier. The observation that "Jobs built the iPhone, but it ran because Ritchie wrote C and UNIX" circulated widely on social media — and it was substantially correct. The XNU kernel inside macOS and iOS is a hybrid of BSD and Mach, both of them UNIX descendants. Ritchie's work sat under Jobs's products as their literal foundation.

Ritchie remained, to the end, a working scientist at Bell Labs. He founded no startup, took no professorship, wrote no books for the general reader. Beyond royalties from K&R, he left little estate. In his obituary Brian Kernighan wrote that he was "modest, courteous and, so far as we ever saw, the most intellectually honest person we knew."

The claim that contemporary computer culture cannot be imagined without C and UNIX is not hyperbole. Ritchie built the kind of substrate that is invisible while it works and noticed only when it fails. He, too, was that sort of presence; and he left, very quietly, in much the same way.