Intel 4004

The Intel 4004 is a four-bit microprocessor introduced in 1971 for the Busicom 141-PF calculator. It integrated a processor’s arithmetic and control functions onto a single chip.

4004 instruction set: The operations encoded for execution by the Intel 4004, including arithmetic, data movement, and control instructions. These instructions defined what the processor could do within its four-bit architecture.
Busicom 141-PF: A desktop printing calculator whose design prompted Intel’s development of the 4004 chipset. Its calculator requirements shaped the processor’s instruction set and companion chips.
Microprocessor: A processor whose central functions are implemented in one or a small number of integrated circuits. The 4004 became an early commercial example of this device class.
Hardwired control unit: A processor control system whose operations are determined by fixed logic rather than stored microinstructions. The 4004’s control was implemented with logic on the chip, unlike control built from programmed microcode.
Intel 4004 architecture: The processor design built around a four-bit datapath, instruction control, and limited on-chip storage. Its architecture explains how a compact chip executed calculator programs.
Busicom: A Japanese company that commissioned Intel to design chips for a family of electronic calculators. Busicom’s contract supplied the commercial need behind the 4004.
Intel 8008: An eight-bit Intel microprocessor introduced in 1972, developed from a separate customer project. It followed the 4004 and extended Intel’s early processor work to eight-bit computing.
Bit-slice processor: A processor assembled from modular chips, each handling part of a word’s arithmetic or control. The 4004 integrated processor functions instead of requiring a board of bit-slice components.
Intel 4001: A companion chip that combined read-only memory with input/output ports for the MCS-4 system. The 4004 fetched calculator instructions from 4001 program-memory chips.
Federico Faggin: An Italian-American physicist and engineer who led the 4004’s chip design at Intel. He drove the silicon-gate implementation that made the processor practical.

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