-113;
binary of 113 = 1110001
2's comp of any binary number: (go from right to left)
rule 1: if any 0 occurs, ignore it.
rule 2: first 1, ignore it.
rule 3: complement every digit.
2's comp of 1110001 = 0001111 (first rule not applied, because there is no 0's)
113 = 0001111 (in 2's comp)
-113 = 10001111 (1 in mbs for -ve)