Adders

Building an Adder The Boolean operations can be built electronically using transistors. Applying an electrical current to a terminal is the equivalent to 1 or True. No current means 0 or False. Using a combination of these operations wired together, we can do simple arithmetic. Further combinations and the use of electronic storage enable use to do more complex calculations.

A D B E Adder AND XOR This adds the inputs A and B. binary decimal 00 01 1 10 2 11 3 B XOR E This adds the inputs A and B. The output is shown by D and E together.

Input Output A B D E DE 00 1 01 10 2 + + + + p q p AND q 1 p q p XOR q 1 p q p XOR q 1 binary decimal 00 01 1 10 2 11 3 Input Output A B D E DE 00 1 01 10 2 + + + +

D A G B F E H C AND XOR AND XOR XOR This adds the inputs A, B and C. The output is shown by G and H together.

Input Output A B C D E F G H GH 00 1 01 10 2 11 3 + + + + + + + + + + binary decimal 00 01 1 10 2 11 3 Input Output A B C D E F G H GH 00 1 01 10 2 11 3 + + + + + + + + + + + + + + + +