Question

A computer's cpu consists of millions of tiny switches called

Answer 1

A computers's cpu consists of millions of tiny switches called Transistors.

Answer 2

A computer's CPU (Central Processing Unit) has millions of tiny switches called transistors.

The transistors are the small semiconductor devices which are used in almost every major electronic device. Actually, the reason behind the use of transistors in the 'Central Processing Unit' (CPU) of the computer is that the CPU requires a lot of logic gates for the purpose of processing the data and making logical calculations. And since if you scrap away all the abstraction layers, you'll find that  the computer works on binary at the most basic level. So, it's a must to have logic gates. And usually NMOS and PMOS transistors are used for building up these logic gates.