Multiplication of bits in twos complement form

Question

Please help me with the following two's complement multiplication logic.

                     Actual      cropped

Unsigned 5 [101] 3 [011] 15 [001111] 7 [111]

Two’s comp. −3 [101] 3 [011] −9 [110111] −1 [111]

I cant understand how actual multiplication is different for unsigned and two's complement multiplication when bit for both are same.

Answer 1

Multiplication for signed and unsigned integers is performed by different rules (unlike addition and subtraction, for example).

The same bits can represent different data, actual interpretation depends on type.