Analog Computers

There are two distinct families of computing device available to us today, the all pervasive digital computer and almost forgotten analog computer. These two types of computer operate on quite different principles.

The digital computer is a sequential device, in general, operating on data one step at a time, in addition the digital computer represents data internally using a quite verbose but very robust form of representation called binary. Thus a single transistor in a digital computer can only store two states, on and off. Obviously to store a number to any sensible degree of precision, many transistors are required.

An analog computer operates in a completely opposite way to the digital computer. For a start, all operations in an analog computer are performed in parallel. Secondly, data are represented in an analog computer as voltages, a very compact but not necessarily robust form of storage (prone to noise corruption). A single capacitor (equivalent to the digital computer's use of a transistor) in an analog computer can represent one continuous variable.

EC-1 Educational Analog Computer, introduced in 1960 by Heathkit

The Heathkit Educational Analog Computer is completely self-contained and contains nine DC operational amplifiers with provision for balancing without removing problem setup. It also features three initial condition power supplies, five coefficient potentiometers, four sets of relay contacts, an electronically regulated power supply and a built-in repetitive oscillator for automatic operation. The complete EC-1 kit also contains an assortment of precision resistors, capacitors, special silicon diodes and patch cords for setting up scores of complex computer problems easily and accurately.

Vannevar Bush's differential analyzer

The world's first electronic analog computer filled a room at the Massachusetts Institute of Technology. Vannevar Bush's differential analyzer crunched through calculus in seconds, although technicians often spent hours setting it up to solve an equation. A labyrinth of wheels, discs, shafts and gears handled the brainwork with precision unmatched by any contemporaneous machine. But its heyday was short, as digital computers developed after World War II put the analyzer out to pasture.