This shows how computer add numbers.
By swiching individual logics you add numbers together. The answer is in binnary so:
First row : logic source/lamp(answer) = 1
Second row : 2
Third row : 4
Fourth row : 8
This circuit can add numbers up to 15. You can add more but you will get lost.
Motivation and knowledge for making this circuit I got from youtube channel called:
"In One Lesson", There are few interesting videos about how CPU works (The best I have ever watched, so if you ever wonder how it works, check it out).
