1. Subtraction can be performed using addition by taking the complement of the subtrahend and adding it to the minuend.
2. The 1's complement of a binary number is obtained by flipping all bits, and 1's complement subtraction involves taking the complement of the smaller number and adding it to the larger number.
3. The 2's complement is obtained by adding 1 to the 1's complement, and 2's complement subtraction discards any carry when adding the 2's complement of the smaller number to the larger number.