Digital logic for use in logic circuits that are designed to handle more than two levels (voltages, etc.). In q-valued logic there are q levels and each memory element (flip-flops, etc.) can exist in q different states. The classification of logic circuits into combinational and sequential circuits applies to multivalued logic exactly as it does to binary logic.

There is much interest currently in ternary logic (q = 3) and, to a somewhat lesser extent, in quaternary logic (q = 4). Such logics promise reduced numbers of logic gates, memory elements, and—perhaps most significantly—interconnections. Ternary logic is simple to implement in CMOS technology, and is likely to become important in the design of VLSI circuits. Its increased logical richness is shown by the fact that there are 16 possible two-input binary gates, but 19 683 such ternary gates (ignoring degeneracies in both cases).