A small, fast, portable systems language — the language of operating systems, embedded devices, databases and the runtimes of most other languages.

A short history

Year	Milestone
1972	Dennis Ritchie creates C at Bell Labs (successor of B) to rewrite UNIX.
1978	The C Programming Language (K&R) by Kernighan & Ritchie — the de-facto standard, “K&R C”.
1989 / 1990	C89 / C90 — the first ANSI / ISO standard (“ANSI C”). Function prototypes, `void`, `const`.
1999	C99 — `//` comments, `long long`, `<stdint.h>`, `bool`, VLAs, designated initializers, `inline`, mixed declarations.
2011	C11 — `_Generic`, `_Static_assert`, anonymous structs/unions, `<threads.h>`, `<stdatomic.h>`, `_Alignas`; `gets` removed.
2018	C17 (C18) — bug-fix release of C11, no new features. The default standard for these notes.
2024	C23 — `bool`/`true`/`false` as keywords, `nullptr`, `constexpr`, `typeof`, `#embed`, binary literals `0b1010`, `[[attributes]]`.

Why learn C?

The trade-off

C gives you	C does NOT give you
Raw pointers and manual memory control	Garbage collection, bounds checks, null safety
Structs, unions, functions	Classes, inheritance, templates, exceptions
A tiny standard library	Built-in strings, lists, maps, networking
Speed and control	Protection from undefined behaviour — mistakes compile and silently misbehave

Hello, world

C

#include <stdio.h>

int main(void) {
    printf("Hello, world!\n");
    return 0;
}

Output

Hello, world!

Terminal

$ gcc hello.c -o hello        # compile (or: clang hello.c -o hello)
$ ./hello                     # run
Hello, world!
$ echo $?                     # exit status returned by main
0

Is C a high-level or low-level language?

What is the difference between C and C++?