AN/UYK-20

The AN/UYK-20 "Data Processing Set" was a ruggedized small computer manufactured by Univac and used by the United States Navy for small and medium-sized shipboard and shore systems built in the 1970s. It featured non-volatile magnetic core memory and was housed in a heavy-duty metal cube-shaped box which was designed to fit through a 25-inch circular hatch.

In 1972, in response to the proliferation of small computer types in the Navy's inventory, the Chief of Naval Material mandated the use of the AN/UYK-20(V) in systems requiring a small digital processor.

Programmers and operators sometimes colloquially referred to this computer as the "Yuck Twenty."

In addition to various uses throughout the fleet, the system was used to train the U.S. Navy's Data Systems Technicians (DS) on digital computer theory and application. The eight or ten week course was broken into the following sections:
 * Macroinstructions
 * Microinstructions
 * Processor/Emulator
 * Memory
 * Input/Output
 * Graded Troubleshooting (Mids)

The AN/UYK-20 is still currently in use, but has been largely supplanted by the AN/UYK-44, which uses a 'superset' of the UYK-20 instruction set, meaning the UYK-44 will execute all of the UYK-20 instructions, as well as several new instructions specific to the UYK-44.