Ternary computer

Ternary computers (also sometimes referred to as trinary) use three-valued logic in their calculations.

History

One of the earliest calculating machines, built by Thomas Fowler entirely from wood in 1840, was a ternary computer. The modern ternary computer (Setun, ...) was built in the late 1950s in the Soviet Union at the Moscow State University, and it had notable advantages to the binary computers (as lower electricity consumption and lower production cost) which eventually replaced it.

Balanced ternary

Ternary computing is commonly implemented in terms of balanced ternary, which uses the three digits -1, 0, and +1. The negative value of any balanced ternary number can be obtained by replacing every + with a – and vice versa. It is easy to subtract a number by inverting the + and – digits and then using normal addition. Balanced ternary can express negative values as easily as positive ones, without the need for a leading negative sign as with decimal numbers. These advantages make some calculations more efficient in ternary than binary.

"I often reflect that had the Ternary instead of the binary Notation been adopted in the Infancy of Society, machines something like the present would long ere this have been common, as the transition from mental to mechanical calculation would have been so very obvious and simple". (Fowler, 1840)

The future

With the advent of mass-produced binary components for computers, ternary computers have diminished to a small footnote in the history of computing. However, ternary logic's elegance and efficiency is predicted by Donald Knuth to bring them back into development in the future^[1]. Possible ways on how this can happen is by the combination of an optic computer with the ternary logic system ^[2] This future potential has also been remarked by certain companies as Hypres which is actively engaged in ternary computing. IBM too still infrequently reports on ternary computing topics (in its papers), yet is not actively engaged in it.