The world' s first microprocessor, released in 1971. The 4004 contained 2300 transistors (compared wITh 5.5 million in the 1996 Pentium Pro) and was intended for use in a calculator. IT processed data in 4 bITs, but ITs instructions were 8 bITs long. Program and Data memory were separate, IT had 1 kilobyte of data memory and a 12-bITPC for 4K of program memory (in the form of a 4 level stack, used for CALL and RET instructions). There were also sixteen 4-bIT (or eight 8-bIT) general purpose registers. The 4004 had 46 instructions. (1997-03-30)