Conversions and Casts

Implicit conversions

C silently converts in mixed expressions — the "usual arithmetic conversions": the smaller/weaker type is promoted to the wider one.

int i = 3;
double d = i;          // int -> double, exact: 3.0
double half = i / 2;   // int / int FIRST (0), then int -> double: 0.0!
double ok = i / 2.0;   // i promoted to double: 1.5

The assignment case truncates the other way: int x = 2.9; stores 2 — the fraction is dropped, not rounded.

Explicit casts

A cast says "convert on purpose":

double avg = (double)total / count;   // divide as doubles
int rounded = (int)(x + 0.5);         // round-half-up for positive x
char c = (char)('A' + 3);             // int -> char

Cast when you mean it; never to silence a warning you do not understand.