Quiz Entry - updated: 2026.07.14
What are the C keywords (reserved words)?
32 reserved words in C89/90 (types, modifiers, storage classes, control flow, and a few operators), with more added by later standards.
| Category | Keywords |
|---|---|
| Data types | char, short, int, long, float, double, void |
| Type modifiers | signed, unsigned, const, volatile |
| Storage class | auto, register, static, extern |
| Control flow | if, else, switch, case, default, for, while, do, break, continue, goto, return |
| User types | struct, union, enum, typedef |
| Operators | sizeof |
Cannot use these as identifiers:
// ERROR: 'if' is a keyword
int if = 5;
// OK in C (but not in C++)
int class = 10;
C99 additions: inline, restrict, _Bool, _Complex, _Imaginary
C11 additions: _Alignas, _Alignof, _Atomic, _Generic, _Noreturn, _Static_assert, _Thread_local
Tip: Keywords starting with _ and uppercase are reserved for future standards.