Types & sizeof in C
From the C cheat sheet · Variables & Types · verified Jul 2026
Types & sizeof
C's built-in types and their sizes.
c
// Quick Reference
int i = 42;
long l = 42L;
double d = 3.14;
char c = 'A';
unsigned u = 10;
bool ok = true; // C23 keyword💡 In C23, bool/true/false are keywords - older C needed #include <stdbool.h>.
⚡ Type sizes are platform-dependent; use <stdint.h> (int32_t) when the width matters.
📌 Print sizeof (a size_t) with %zu; using %d there is technically wrong.
🟢 unsigned types wrap around on overflow; signed integer overflow is undefined behavior.
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