Intel 4004 definition processor
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-bit PC
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.