Research

An analog computer (spelled analogue in British English) is a form of computer that uses electrical, mechanical or hydraulic phenomena to model the problem being solved. More generally an analog computer uses one kind of physical quantity to represent the behaviour of another physical system, or mathematical function. Modeling a real physical system in a computer is called simulation.

The computer as described above is essentially just a calculator, and a very simple one at that. To be of any significant use in scientific problem solving, the computer must become programmable, in the sense that the sequence of calculations and decision making criteria to direct the calculations can be set out and made to control the sequence of steps taken by the calculator. The set of instructions which describe the process is called a program, and any programmable computer must have circuitry to allow it to execute the instruction sequence described in such a program. At the lowest level, the program is written in machine code, which is in a format appropriate for direct interpretation by the computer circuitry as the computer reads the instruction sequence from some source, such as the computer's memory. This language level is very far from any human language, and thus quite inappropriate for the description of the methods to solve scientific problems.

The history of computers is not all digital, from the humble slide rule to hydraulic models of the economy there is a rich history of both electronic and mechanical analog computers. Here are some of our favorite examples. These computers have certain advantages over their symbolic counterparts. They measure continuous variables in parallel and therefore their accuracy is limited only by the granularity with which their results are read and their speed is not limited by sequential operations.

This page contains a variety of analog computer impressions - most of these machines have been scrapped a long time ago (which really makes me feel sad). Where ever possible picture sources are cited, but in many cases I have no idea where the pictures came from. I hope that I do not violate any ones copyright with this collection of pictures. The pictures are shown for academic purposes only to keep these machines from getting forgotten.

Electronic analog computers may seem to be "simple" or "like a toy computer", in fact they are powerful tools that were used during the 1950s and 1960s to design and test systems like ICBMs, supersonic aircraft and spacecraft. But the analog computer can be used to model any physical system that can be described by mathematical formulas, even more mundane ones from modeling the effects of pollution on the fish population in a river to fine tuning the suspension on a new car design. Analog computers will not only test a fixed design but also allows variables to be quickly changed to test "what if" conditions. By scaling time as an independent variable, physical processes that happen quickly can be stretched out, and processes that happen over a long period can be shortened to make the process easier to study. And it is very easy to study variables at any point in the program while it is running to find faults in the program design.

OMR is an acronym for Optical Mark Recognition/Optical Mark Reader. OMR is now used for data entry. In the early’s OMR used two forms that were punched cards and paper tape which used actual holes instead of filling up the bubbles which we use in modern OMR.

Blaise Pascal invented the mechanical calculator in 1642. He conceived the idea while trying to help his father who had been assigned the task of reorganizing the tax revenues of the French province of Haute-Normandie ; first called Arithmetic Machine, Pascal's Calculator and later Pascaline, it could add and subtract directly and multiply and divide by repetition.

The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.

Napier's bones is an abacus created by John Napier for calculation of products and quotients of numbers that was based on Arab mathematics and lattice multiplication used by Matrakci Nasuh in the Umdet-ul Hisab and Fibonacci writing in the Liber Abaci. Also called Rabdology. Napier published his version of rods in a work printed in Edinburgh, Scotland, at the end of 1617 entitled Rabdologiæ. Using the multiplication tables embedded in the rods, multiplication can be reduced to addition operations and division to subtractions. More advanced use of the rods can even extract square roots. Note that Napier's bones are not the same as logarithms, with which Napier's name is also associated.

Since this book, first published in 1986, is still the most comprehensive history of machine translation (up to 1985), I am making the whole text available for researchers. Copyright remains with me and the publishers (Ellis Horwood). Publication and multiple-copy reproduction (in any form and for any purpose) of the whole or any part of the text is forbidden, except after prior permission from me and the publishers. However, single copies of sections or chapters may be made by individuals for private personal use only.