A microprocessor (abbreviated as µP or uP) is an electronic computer central processing unit (CPU) made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (aka microchip or just chip). Before the advent of microprocessors, electronic CPUs were made from discrete (separate) TTL integrated circuits; before that, individual transistors; and before that, from vacuum tubes. There have even been designs for simple computing machines ...