If we baked 10 cookies and gave them out in batches of 3, how many would we have leftover after giving out all the full batches we could?

The modulo operator %, gives us the remainder after two numbers are divided.

int cookiesBaked = 10;
int cookiesLeftover = 10 % 3;
//cookiesLeftover holds 1

You have 1 cookie left after giving out all the batches of 3 you could!

Modulo can be a tricky concept, so let’s try another example.

Imagine we need to know whether a number is even or odd. An even number is divisible by 2.

Modulo can help! Dividing an even number by 2 will have a remainder of 0. Dividing an odd number by 2 will have a remainder of 1.

7 % 2
// 1, odd!
8 % 2
// 0, even!
9 % 2
// 1, odd!