Using shift operator for faster division and multiplication

Multiplications

12 * 2    =  12 << 1
12 * 4    =  12 << 2
12 * 8    =  12 << 3
12 * 16   =  12 << 4
12 * 32   =  12 << 5
12 * 64   =  12 << 6
12 * 128  =  12 << 7
12 * 256  =  12 << 8

Divisions

12 / 2    =  12 >> 1
12 / 4    =  12 >> 2
12 / 8    =  12 >> 3
12 / 16   =  12 >> 4
12 / 32   =  12 >> 5
12 / 64   =  12 >> 6
12 / 128  =  12 >> 7
12 / 256  =  12 >> 8