HISTORY OF COMPUTERS
Historically, the most important early computing instrument is the abacus, which has been known widely for more than 2,000 years. Another computing instrument, the astrolabe, was also in use about 2,000 years ago for navigation.
Blaise Pascal is widely credited with the building of the first “digital calculating machine” in 1642. It performed only additions of numbers entered by means of dials and was intended to help Pascal’s father, who was a tax collector. In 1671, Gottfried Wilhelm von Leibniz invented a computer that was built in 1964; it could add and, by successive adding and shifting, multiply. Leibniz invented a special “stepped gear” mechanism for introducing the addend digits, and this mechanism is still in use. The prototypes built by Leibniz and Pascal were not widely used but remained curiosities until more than a century later, when Tomas of Colmar ( Charles Xavier Thomas ) developed (1820) the first commercially successful mechanical calculator that could add, subtract, multiply, and divide. A succession of improved “desk-top” mechanical calculators by various inventors followed, so that by about 1890, the available built-in operations included accumulation of partial results, and printing of results, each requiring manual initiation. These improvements were made primarily to suit commercial users, with little attention given to the needs of science.
While Thomas of Colmar was developing the desk-top calculator a series of very remarkable developments in computers was initiated in Cambridge, England, by Charles Babbage. Babbage realized (1812) that many long computations, especially those needed to prepare mathematical tables, consisted of routine operations that were regularly repeated; from this he surmised that it ought to be possible to do these operations automatically. He began to design an automatic mechanical calculating machine, which he called a “difference engine”, and by 1822 he has built a small working model for demonstration. With financial help from the British government, Babbage started construction of a full-scale difference engine in 1823. It was intended to be steam-powered; fully automatic, even to the printing of the resulting tables; and commanded by a fixed instruction program.
The difference engine, although of limited flexibility and applicability, was conceptually a great advance. Babbbage continued work on it for 10 years, but in 1833 he lost interest because he had a “better idea”—the construction of what today would be described as a general-purpose, fully program-controlled, automatic mechanical digital computer. Babbage called his machine an “analytical engine”; the characteristics aimed at by this design show true prescience, although this could not be fully appreciated until more than a century later. The plans for the analytical engine specified a parallel decimal computer operating on numbers (words) of 50 decimal digits and provided with a storage capacity (memory) of 1,000 such numbers. Built-in operations were to include everything that a modern general-purpose computer would need, even the all important “conditional control transfer” capability, which would allow instructions to be executed in any order, not just in numerical sequence. The analytical engine was to use Punched Cards (similar to those used in Jacquard loom), which were to be read into the machine from any of several reading stations. It was designed to operate automatically, by steam power, with only one attendant.
Babbage’s computers were never completed.
Various reasons are advanced for his failure, most frequently, the lack
of precision machining techniques at the time.
Another conjecture is that Babbage was working on the solution of a problem that few people in 1840 urgently needed to solve.
After Babbage, there was a temporary loss of interest in automatic digital computers. Between 1850-1900 great advances were made in mathematical physics, and it came to be understood that most observable dynamic phenomena can be characterized by differential equations, so that ready means for their solution and for the solution of other problems of calculus would be helpful. Moreover, from a practical standpoint, the availability of steam power caused manufacturing, transportation, and commerce to thrive and led to a period of great engineering achievement. The designing of railroads and the construction of steamships, textile mills, and bridges required differential calculus to determine such quantities as centers of gravity, centers of buoyancy, moments of inertia, and stress distributions; even the evaluation of the power output of a steam engine required practical mathematical integration. A strong need thus developed for a machine that could rapidly perform many repetitive calculations.
USE OF PUNCHED CARDS BY HOLLERITH
A step toward automated computation was the introduction of punched cards, which were first successfully used in connection with the computing in 1890 by Herman Hollerith and James Powers, working for the U.S. Census Bureau. They developed devices that could automatically read the information that been punched into cards, without human intermediation. Reading errors were
consequently greatly reduced, work flow was increased and, more important, stacks of punched cards could be used as an accessible memory store of almost unlimited capacity; furthermore, different problems could be stored on different batches of cards and worked on as needed.
These advantages were noted by commercial interests and soon led to the development of improved punched-card business-machine systems by International Business Machines (IBM), and other companies. These systems used electromechanical devices, in which electrical power provided mechanical motion—such as for turning the wheels of an adding machine. Such systems soon included features to feed in automatically a specified number of cards form a “read-in” station; perform operation such as addition, multiplication, and sorting; and feed out cards punched with results. The machines were slow, typically processing from 50-250 cards per minute, with each card holding up to 80 decimal numbers. At the time, however, punched cards were an enormous step forward.