What is the purposes of hybrid computer?

A hybrid computer is a type of computer that is no longer made. It contains two interconnected computers: a digital computer and an analog computer. In most hybrid computers, part of the analog computer's program is entered manually by plugwires on plugboards and part by the digital computer switching relays and setting digitally controlled pots. The digital computer program was entered from tape or disk.

Most of them were custom built systems generally used for control system simulation modeling. The analog computer was programmed to model an open loop real world system and the digital computer was programmed to control it and thereby close the loop. Some systems tested this way were:

• Nuclear Reactor control systems
• Aircraft flight control systems
• Chemical reaction control systems
• Industrial process control systems
• etc.

Another use of hybrid computers was high speed drawing of "stroke graphics" (dots, vectors, arcs) on random deflection high brightness CRT displays (another long gone technology).

The last hybrid computers I saw operating were in about 1986. Haven't heard of any made since then.