for_loop

for(initalise, test, update)

for (expr1; expr2; expr3) {
body;
}

Is (almost always) equivalent to

expr1;
while (expr2)
{
body;
expr3;
}

the edge case is that technically expr3 is not in the compound statement.

non-example of while loop equivelancy

For loops are slightly different to while loops as expr3 is run every iteration.

n = 0;
while (n < 10) { // infinite loop
    continue;
    n++
}

Is not equivalent to.

for (n = 0; n < 10; n++){ // not an infinite loop
    continue;
}

omitting expressions in the for loop is legal. for(;;) is an infinite loop and is valid for(;i < 0;) is equivalent to while(i < 0)

for(int i; i < n; i++){ } in c99 the i variable cannot be accessed outside the for loop.

Also see the [[operator___20240603_115338#comma operator|comma operator]]