Reversible and endoreversible computing

Reversible combinatorial computers are built from basic cells with a three-bit digital input and a three-bit digital output. Such a computer can calculate both from left to right and from right to left, such that input pins and output pins are indistinguishable. In order to perform a calculation in a specific direction, an electric field should be applied externally. The inevitably frictional losses occur in the lines supplying the computer with the input data and in the lines draining the calculation results to the output registers. Such behavior is analogous to the endoreversible operation of heat engines and other energy converters.