What a full adder does
A full adder combines three input bits and produces two outputs:
- Sum: the bit result of the addition
- Carry: the bit passed to the next position
For each problem, your goal is to find the correct outputs and then simplify the final answer if the exercise gives an expression.
Method
- Identify the three inputs.
Write them clearly and check that each one is a bit, so it is either 0 or 1.
- Add the inputs.
Treat the three bits as a small binary sum.
- Separate the result.
- The sum output is the rightmost bit of the binary result.
- The carry output is 1 when the total is 2 or 3, and 0 when the total is 0 or 1.
- Simplify the final answer.
If the answer is written as an expression, reduce it to its simplest correct form.
Quick check
Use the total number of 1s as a check:
- 0 or 1 one → carry 0
- 2 or 3 ones → carry 1
Then confirm the sum output matches the binary remainder.
Example idea
If the three inputs add to 2, the outputs are sum = 0 and carry = 1. Always verify that the two outputs together represent the same total as the inputs.