| Adder | |||||||||||||
| In order to construct a CPU, we need to perform arithmetic and logical operations. | |||||||||||||
| Basic arithmetic operator: addition | |||||||||||||
| What's involved in adding binary numbers? | |||||||||||||
| carry | 0 | 1 | 1 | 0 | decimal | ||||||||
| 0 | 0 | 1 | 1 | 3 | |||||||||
| 0 | 1 | 1 | 0 | 6 | |||||||||
| result | 1 | 0 | 0 | 1 | 9 | ||||||||
| In each column: | |||||||||||||
| input: add 2 bits, along with a carry bit from the previous result | |||||||||||||
| output: 1 bit result, 1 bit carry | |||||||||||||