Remainder and Odd/Even Check

Remainder and Odd/Even Checks

The remainder operator % is one of the most useful tricks in C.

The remainder operator

% gives what is left over after a division:

printf("%d\n", 7 % 2);   // 1
printf("%d\n", 7 % 3);   // 1
printf("%d\n", 12 % 6);  // 0

The even-number check

x % 2 == 0 is true exactly when x is even:

int x = 8;
if (x % 2 == 0) {
    printf("Even");
}

Quotient and remainder together

10 / 4 is the quotient (2) and 10 % 4 is the remainder (2). Together they cover everything a division leaves behind.

TL;DR

• % gives the remainder of a division.
• Check even numbers with x % 2 == 0.
• Quotient comes from /, remainder from %.
• a % b is always 0 when b divides a evenly.