Linux Format



We’ve painted a picture of analogue and digital computers as being totally unconnecte­d, but this wasn’t always the case. An analogue computer can be connected to a digital computer, and the combinatio­n is referred to as a hybrid computer. These first appeared in the early ’60s and continued to be used until pure digital computers became fast enough to displace analogue computing.

The analogue computer part generally carried out the simulation by solving differenti­al equations, while the digital computer provided overall control. This was possible by permitting the digital computer to read the outputs of the summers and integrator­s using analogueto-digital converters, to adjust potentiome­ter values, and to switch the operationa­l mode of the analogue computer – for example, between Run, Hold (not included in our emulator, this mode stopped integrator­s integratin­g, thus halting the computatio­n) and IC. A classic example is an optimisati­on problem. Let’s say we have a mathematic­al model of the trajectory of a projectile, and we want to adjust the angle of launch until we achieve a particular range. This is a trial and error process, but doing it manually on a pure analogue computer could be a laborious and timeconsum­ing sequence of setting the angle, running the simulation, observing the result, resetting the angle, running another simulation, and so on. All this changes with a hybrid computer. Although it would do the same sort of thing, it would do some more quickly by eliminatin­g the need for human interventi­on.

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