Central processing unit (CPU) on a single silicon chip (called microchip) that can be 'soft wired' by using different programming instructions. When coupled with memory and input-output devices, a microprocessor becomes a microcomputer. Intel 4004, one of the earliest microprocessors, had a 4-bit data bus and could address 4.5 kilobytes of memory. The first mass produced microprocessor was Intel 8080 that in 1973 cost about $400.