The Core Types: int, char, float, double

The everyday types

| Type | Typical size | Holds | |---|---|---| | int | 4 bytes | whole numbers, about ±2.1 billion | | char | 1 byte | one character — and a small integer (-128..127) | | float | 4 bytes | approximate real numbers, ~7 significant digits | | double | 8 bytes | approximate real numbers, ~15 significant digits |

Sizes are typical, not guaranteed — that is what sizeof (next lesson) is for. %zu prints a size_t (what sizeof returns).

char is a number

char c = 'A';        // character literal — a single quote
printf("%d\n", c);   // 65 — the ASCII code
printf("%c\n", c);   // A

'A' + 1 is 'B'. This identity between characters and small integers powers text processing in C.

signed and unsigned

An int is signed by default: it can be negative. unsigned int drops the sign and doubles the positive range. Mixing them in one expression is a classic bug source — for now, keep arithmetic in signed types.

float vs double

float rounds sooner. Default your real-number work to double (printf("%f", ...) prints a double).