The equal sign is combined with the +, -, *, /, div and % operators to give the following shorthand versions of standard arithmetic operations:
a += b instead of a = a + b
a -= b instead of a = a - b
a *= b instead of a = a * b
a /= b instead of a = a / b
a div= b instead of a = a div b
a %= b instead of a = a % b