The C Language — Dennis Ritchie

C was born because someone wanted to move UNIX to a different machine. The point matters.

From B to C

In 1969, Ken Thompson wrote the first UNIX in the assembly language of the PDP-7. In 1970, as UNIX was being moved to the PDP-11, he implemented a small high-level language he called B and began rewriting parts of UNIX's utilities in it.

But B had limits. It had no type system; every value was treated as a machine word. Handling characters or structures efficiently was awkward, and B could not exploit the PDP-11's rich addressing modes or 8-bit and 16-bit data types.

From 1971 to 1973, Dennis Ritchie extended B incrementally. What emerged—first called "New B"—became, by about 1972, recognisably the C of later years.

1973 — Rewriting UNIX in C

What made C historically decisive was the 1973 rewrite of UNIX itself in C.

Before this, no one had written an operating system in anything other than assembly. The OS and its hardware were inseparable. (Multics had used PL/I as a counterexample, but Multics was not, commercially, a success.)

For Bell Labs, the rewrite was an expensive short-term choice. The assembly version of UNIX existed and worked; throwing it away to redo the same work in an immature in-house language was, by ordinary management logic, indefensible.

It was also the choice that made UNIX portable. Where there was a C compiler, there was an OS. In 1977 UNIX was successfully ported to the Interdata 8/32, severing it from the PDP-11. From that moment, UNIX—and any OS that followed the same approach—was no longer tied to a single machine.

K&R

What put C in front of the world was the 1978 book by Brian Kernighan and Dennis Ritchie, The C Programming Language—universally known as K&R. Fewer than 230 pages. A complete language presented concisely.

K&R has been cited, repeatedly, as one of the most influential programming books ever written. The terseness of the prose, the smallness of the examples, the visible design behind it—the next generation of language designers learned C this way. Bjarne Stroustrup (C++), Brad Cox (Objective-C), Anders Hejlsberg (Turbo Pascal, C#, TypeScript), Linus Torvalds (Linux), Yukihiro Matsumoto (Ruby)—essentially all of them came up through K&R.

Half a Century Later

In 2026, C remains one of the most widely used languages in the world. The Linux kernel, the Windows kernel, the cores of macOS and iOS, the Android system layer, databases, web servers, embedded firmware—nearly everything beneath the application layer of modern computing still runs C.

A vertical stack of languages, descended from C, sits on top of it. C++ (1985), Objective-C (1984), Java (1995), C# (2000), Go (2009), Rust (2010), Zig (2016)—each, with its own syntax and design, defines itself against C in some way.

Dennis Ritchie died at home on 12 October 2011, quietly. Steve Jobs had died a week earlier; the coverage that day was Jobs. Outside the technical press, Ritchie's death was scarcely noted.

But of the computers operating in the world that day, more than nine in ten were—somewhere down the stack—executing the language he had designed.