Remember the bit shift operation? « and »? Well if we left shift a number, we are multiplying that number by a power of two. For example, 1 = 0001. If we left shift it by 1, we’ll have 1 « 1 = 0010 = 2 = 1 * 2^1. If we left shift it by 2, we’ll have 1 « 2 = 0100 = 4 = 1 * 2^2. Thus, the general formula is:
a << b = a \* 2^b