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Mind, Machines and Victorian Computing
From: Science Museum
| By:
Doron Swade |
EDITOR'S INTRODUCTION |
Charles Babbage was one of the first designers of automatic calculating machines. His designs of vast mechanical calculating engines rank among the startling intellectual achievements of the nineteenth century. Although his work did not reach practical fruition in his lifetime, the partial constructions he did achieve represent the first successful embodiment of mathematical rule in mechanism--the replacement and extension of an office of human thought through mechanism. His work led him from mechanical arithmetic to fully-fledged computing. Doron Swade, assistant director and head of collections at the Science Museum, is an expert on the life and work of Charles Babbage and will be giving a paper exploring the significance of the birth of computing at the Locating the Victorians Conference in London, July 2001. Here he presents a fascinating introduction to a particularly important development in the history of science. |
he early decades of the nineteenth century were a time of unprecedented engineering ambition. Machines were the obsession of the age. Newspapers and scientific magazines trumpeted inventions, contraptions and mechanical novelties, reported with all seriousness, though many were clearly fanciful. |
Charles Babbage (1791-1871) was an English gentleman of science and an accomplished mathematician. 
He was born into an age when mathematical calculation relied not on calculating machines but on printed tables. Architects, engineers, scientists, bankers, insurers, actuaries and journeymen relied on these tables for calculation. One of the key applications of mathematical tables was navigation. Ships determined their position at sea using calculations based on the position of the stars. Errors in tables put life and property at risk. The stakes were high. |
Printed tables had a number of limitations--they handled a limited number of digits and using them required some knowledge of arithmetical procedures.  Moreover, the tables were prepared by human beings. Humans make mistakes and tables tended to be riddled with errors. The genesis episode occurred in 1821 when Babbage was checking a set of mathematical tables with his great friend, the astronomer, John Herschel. They were dismayed by the number of errors they found. 'I wish to God these calculations had been executed by steam!' exclaimed Babbage. The quest to enlist the assistance of machinery dominated the rest of his life. |
The sources of error in mathematical tables were fourfold. The original manual calculation might be wrong; the transcriber copying the results into lists might err; the typesetter might insert an incorrect piece of type in preparing printing plates; and finally, the proofreader might overlook mistakes. |
For Babbage the problem was errors in tables. The solution lay in machines--calculating engines. Infallible machines would, thought Babbage, eliminate all four sources of error at a stroke. The 'unerring certainty of mechanism' would ensure the integrity of the calculation, and if a printing apparatus was made an integral part of the machine then transcription, typesetting and proofreading errors could be avoided too and the fallible human would be eliminated from the process. The machines would automatically calculate and tabulate, producing their results not only on hard copy, but also on stereotype plates from which the tables could be printed. |
Babbage's mission to build these machines failed, but in the course of his attempts he was led from mechanised arithmetic to fully-fledged general purpose computing. |
The first mental leap and Difference Engine No.1
This transition occurred in two stages. The first was automation--the elimination of the need for continuous human intervention.  The handle of an engine could be turned to produce useful results, without the operator needing to understand the mathematical or mechanical principles upon which the machine is based. Babbage spent eleven years designing and developing Difference Engine No. 1, so-called because of the mathematical principle on which it is based--the method of finite differences. The section of the machine completed by Babbage's engineer, Joseph Clement, represents one of the finest examples of precision engineering of the time. But Clement walked out in 1833 after a dispute and the machine was never completed. Had it been it would have consisted of 25,000 parts and weighed between eight and ten tonnes |
This 'finished portion of the unfinished engine' is one of the most celebrated icons in the pre-history of computing.  It is the first automatic calculator and among the earliest ingressions of machinery into psychology: by turning a handle i.e. exerting physical force, the operator could achieve results which up to that point in history could only be accomplished by a mental act--thinking. The notion of a 'thinking machine' was not lost on Babbage or his contemporaries. 'The marvellous pulp and fibre of the brain had been substituted by brass and steel. He [Babbage] had taught wheelwork to think,' wrote a younger contemporary of Babbage's. |
The Analytical Engine
In 1834 Babbage conceived the machine for which he is called the first computer pioneer--the Analytical Engine. It remains utterly extraordinary that his designs embody, in mechanical form, virtually every essential logical feature of a modern electronic digital computer. The internal architecture of the Analytical Engine pre-echoes developments articulated over a hundred years later--during the early work on electronic machines in the 1940's. It features conditional branching--'if . . . then . . .' statements, i.e., automatically taking alternative courses of action depending on a particular result; 'looping' (repeating the same sequence of instructions); microprogramming; and pipelining--computational techniques assumed to be part of the 'modern' electronic age. The Analytical Engine has an internal repertoire of operations--automatic addition, subtraction, multiplication and division. Perhaps most importantly, it could be programmed using punched cards. In this way the user could instruct the machine to perform any sequence of operations in any order, any number of times, and take conditional action depending on the outcomes. Babbage worked on the design for the Analytical Engine on and off for the rest of his life but the machine was never built. A small experimental section was under construction at the time of his death in 1871. The whole machine would have been larger than a very big steam locomotive. |
The Difference Engine, although elaborate, was still a calculator and could only perform the specific functions it was designed to execute. It crunches numbers the only way it knows how. The Analytical Engine is a general- purpose programmable machine and had the potential to perform any calculation that could be expressed in algebraic notation. |
The second mental leap
Elaborate and versatile as his engine designs were, the context of the machines, for Babbage at least, was entirely mathematical: Babbage does not appear to have conceived of his machines as operating or manipulating entities other than numbers. The crucial step from mechanised arithmetic to computing appears to have been made not by Babbage but by Ada Lovelace, Byron's only legitimate daughter who met Babbage in 1833 at a society party. |
Entranced by the engines and their exuberant inventor, Lovelace became impassioned by the larger implications of automatic computation and published the first account in English on the Analytical Engine.  In this Lovelace took the crucial step in speculating that computing engines might manipulate symbols of which number was only one example. In other words numbers could represent entities other than quantity and a number-manipulating machine need not be confined to arithmetical process. She speculated that if the machine was taught the rules of harmony it could compose music; if it was taught grammar it could compose verse. Nowhere, at least in his published writings, does Babbage consider his inventions outside the context of mathematics. The notion of a 'computer' as a generalised symbol manipulator rather than only a number-cruncher represents the crucial transition in the development of the modern computer. |
Babbage's work and Lovelace's visionary speculations had no discernable influence on the development of the modern computer. The principles of computing embodied in Babbage's and Lovelace's work were reinvented in the electronic era largely in ignorance of what had gone before. Although there is no direct line of influence between the nineteenth century and the modern electronic digital computer, there is nonetheless a thread of continuity. The legend of Babbage and his works was not forgotten by the small band of scientists and engineers who continued to involve themselves in tabulation. What is astonishing is not only the technical ambitions of the designs but that the fundamental principles of computation were conceived in the nineteenth century by Babbage working in a mechanical rather than electronic medium. |
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