Whatever is at A is the opposite of OUT
Logic Gates
A B C
1 1 1 <--- Or Truth table
0 1 1
0 0 0
1 0 1
Half Adder
1 1 1 <--- Or Truth table
0 1 1
0 0 0
1 0 1
Half Adder
This half adder adds two binary digits A and B and has two outputs: sum (s) and carry (c) however it doesn't provide a full sum.
XOR Gate
However there is a more efficient way of doing this in one gate the XOR which matches up to the truth table of the sum as it does the job of the Or and AND.