Unconventional computing.

Unconventional computing

Over time, computers evolved from mechanical computers and eventually from vacuum tubes to transistors . However, conceptually computational systems as flexible as a personal computer can be built out of almost anything. For example, a computer can be made out of billiard balls (billiard ball computer ); a often quoted example. [citation needed ] More realistically, modern computers are made out oftransistors made of photolithographed semiconductors .