The half adder is an example of a simple, functional digital circuit built from two logic gates. The half adder adds two one-bit binary numbers (AB). The output is the sum of the two bits (S) and the carry (C).
The truth table for a half-adder is:
| X |
Y |
C |
S |
| 0 |
0 |
0 |
0 |
| 0 |
1 |
0 |
1 |
| 1 |
0 |
0 |
1 |
| 1 |
1 |
1 |
0 |
‘x’ and ‘y’ are the two inputs, and S (Sum) and C (Carry) are the two outputs.
The Carry output is ‘O’ unless both the inputs are 1.
‘S’ represents the least significant bit of the sum.
The simplified sum of products (SOP) expressions is:
S = x’y + xy’, C = xy
