Intel introduced the first commercially available single-chip microprocessor, the Intel 4004, in 1971.
The project began in 1969 when Japanese calculator maker Busicom asked Intel to create a chipset for a programmable calculator. Intel engineer Marcian Hoff proposed a more general-purpose design, and Federico Faggin led its implementation with contributions from Stanley Mazor and Busicom engineer Masatoshi Shima.
The 4-bit 4004 contained about 2,300 transistors and was initially designed for Busicom’s 141-PF printing calculator. Production units reached Busicom in March 1971, while Intel publicly announced the processor in November. Its significance was not that it was the first computer processor of any kind, but that it placed a general-purpose CPU on one integrated circuit.
A common mix-up involves Texas Instruments’ TMS0100, announced earlier in September 1971. That chip combined processor, memory, and fixed programming functions and is generally classified as an early microcontroller. The 4004 was designed as a programmable microprocessor using external memory and I/O chips.