The GMC-4 is the only 4-bit microcomputer to be mass-produced in the last 30 years (as of 2009). It was produced by Gakken, a Japanese publisher who distributed it with a magazine attached to a box containing the components required to assemble the computer. It is based on the Texas Instruments TMS1100 microcontroller.
The GMC-4 is a modernized version of Gakken's 1983 Gakken FX-System, also known as the R-165. This system was also sold by Radio Shack as the Science Fair Microcomputer Trainer, but replaced the FX's circuit board with hand-wired circuity assembled by the user using springs to hold short bits of wire.
The purpose of the GMC-4 is education. It provides an accessible way to learn about assembly language and the principles of computing.
References
External links
Description of the kit, assembly language and example programs
Example programs gmc4cc (C Compiler for GMC-4) G4CBASIC