Intel 4004 processor (open), manufactured by the Intel Corporation, United States, 1971.

The first microprocessor to be sold commercially, the Intel 4004, was initially developed for the Busicom calculator. The design process began in 1969 when the Nippon Calculating Machine Corporation commissioned Intel to design 12 custom chips for its new calculator. Intel’s engineers suggested that 4 chips would be sufficient; one of those chips would eventually become the 4004. Later Intel bought back the rights for the chip for $60,000 so that they could produce and sell the chip independently. It was first publicly advertised in a 1971 edition of Electronic News. Meanwhile, the Nippon Corporation went bankrupt and the Busicom calculator was never released.