To multiply and divide by powers of two, use the bitwise shift operator.
dividend / 2^n = (dividend >> n)
factor * 2^n = (factor << n).
bitwise addition and subtraction is done using xor.

1101

±0110

=====

1011

+c(b)

=====

xxxx
Where c(b) is the carry in terms of bits. The carry bits depend on whether it's addition or subtraction that's being performed, and maybe whether the numbers are signed or unsigned.