C Standards (C89/C90 to C23)

The ISO versions of C and what each added.

Easy

C89/C90 — the first standard (ANSI C).
C99 — // comments, stdint.h, bool, inline, variable-length arrays, declarations anywhere.
C11 — threads, atomics, _Generic, _Static_assert, anonymous structs/unions.
C17 — bug-fix release.
C23 — true/false/bool/nullptr keywords, typeof, constexpr objects, binary literals 0b1010, digit separators 1'000'000, #embed. Select one with gcc -std=c17 and say which standard your project uses.

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