Model V
# Model V

The Model V was among the early electromechanical general purpose computers, designed by George Stibitz and built by Bell Telephone Laboratories, operational in 1946.

Only two machines were built: first one was installed at National Advisory Committee for Aeronautics (NACA, later NASA), the second (1947) at the US Army’s Ballistic Research Laboratory (BRL).

## Construction

Design was started in 1944. The tape-controlled (Harvard architecture) machine had two (design allowed for a total of six) processors ("computers") that could operate independently, an early form of multiprocessing.

The Model V weighed about 10 short tons (9.1 t).

## Significance

* Inspired Richard Hamming to investigate the automatic error-correction, which led to invention of Hamming codes
* One of the early electromechanical general purpose computers
* First American machine and first George Stibitz design to use floating-point arithmetic
* Had an early form of multiprocessing
* Had a very primitive form of an operating system, albeit in hardware. A separate hardware control unit existed to direct the sequence of computer operations.

## Model VI

Built and used internally by Bell Telephone Laboratories, operational in 1949.

Simplified version of the Model V (only one processor, about half the relays) but with several improvements, including one of the earliest use of the microcode.

