The TMS1000 is a family of microcontrollers introduced by Texas Instruments in 1974. It combined a 4-bit central processor unit, read-only memory (ROM), random access memory (RAM), and input/output (I/O) lines as a complete "computer on a chip". It was intended for embedded systems in automobiles, appliances, games, and measurement instruments. It was the first high-volume commercial microcontroller (As described later, the predecessor TMS0100 series may not be regarded as microcontrollers). In 1974, chips in this family could be purchased in volume for around $2 each. By 1979 about 26 million parts in this family were sold every year. The TMS 1000 was used in Texas Instruments' own Speak & Spell educational toy, the Big Trak programmable toy vehicle and in the electronic game Simon. History TMS 0100 series The Smithsonian Institution says TI engineers Gary Boone and Michael Cochran succeeded in creating the first microcontroller (also called a microcomputer) in 1971. The TMS1802NC was a single-chip microcontroller which was announced September 17, 1971 and implemented a four-function calculator. The TMS1802NC, despite its designation, was not part of the TMS 1000 series; it was later redesignated TMS0102 as part of the TMS 0100 series, which was used in the TI Datamath calculator and the Sinclair Executive calculator. The TMS0100 series may not be considered microcontrollers. This is because it cannot be used for purposes other than calculators, and cannot execute user-created programs. TMS 1000 series The later TMS 1000 series went on the market in 1974. TI stressed the 4-bit TMS 1000 for use in pre-programmed embedded applications. A computer-on-a-chip combines the microprocessor core (CPU), memory, and I/O (input/output) lines onto one chip. The computer-on-a-chip patent, called the "microcomputer patent" at the time, , was awarded to Gary Boone and Michael J. Cochran of TI. Aside from this patent, the standard meaning of microcomputer is a computer using one or more microprocessors as its CPU(s), while the concept defined in the patent is more akin to a microcontroller. Description The TMS1000 family eventually included variants in both the original PMOS logic and also in NMOS and CMOS. Product variations included different sizes of ROM and RAM, different I/O counts, and ROMless versions intended for development or for use with external ROM. The original TMS1000 had 1024 x 8 bits of ROM, 64 x 4 bits of RAM, and 23 input/output lines. The TMS1000 family used mask-programmed ROM. Once the user