What do all those transistors do?
The CPU in your laptop or desktop has a lot of transistors in it. The Core i7-6700HQ that I'm typing this on has 1.35 billion of the little guys. Buck back in the day on of the earliest computers, ENIAC , had only 20 thousand vacuum tubes which more or less fufilled the same role as transistors do now. So what do all those extra transistors we've added accomplish, if we were able to do useful mathematical operations with just 20,000? Most of the increase in the speed at which we run computers, the clock rate, has come from replacing large and slow transistors with smaller and faster transistors after all. Well first, what was ENIAC doing with it's transistors? A single transistor isn't very useful. If you're willing to use a resistor too you can perform an operation like making an output the logical and of one input and the inverse of a second input, call it AND(A, NOT(B)). But that circuit is a very jury rigged thing which will be slow, ...