The invention: The world’s first electronic general-purpose digital computer.

The people behind the invention:

John Presper Eckert (1919-1995), an American electrical engineer John W. Mauchly (1907-1980), an American physicist John von Neumann (1903-1957), a Hungarian American mathematician
Alan Mathison Turing (1912-1954), an English mathematician

Computer Evolution

In the 1820′s, there was a need for error-free mathematical and astronomical tables for use in navigation, unreliable versions of which were being produced by human “computers.” The problem moved English mathematician and inventor Charles Babbage to design and partially construct some of the earliest prototypes of modern computers, with substantial but inadequate funding from the British government. In the 1880′s, the search by the U.S. Bureau of the Census for a more efficient method of compiling the 1890 census led American inventor Herman Hollerith to devise a punched-card calculator, a machine that reduced by several years the time required to process the data.
The emergence of modern electronic computers began during World War II (1939-1945), when there was an urgent need in the American military for reliable and quickly produced mathematical tables that could be used to aim various types of artillery. The calculation of very complex tables had progressed somewhat since Babbage’s day, and the human computers were being assisted by mechanical calculators. Still, the growing demand for increased accuracy and efficiency was pushing the limits of these machines. Finally, in 1946, following three years of intense work at the University of Pennsylvania’s Moore School of Engineering, John Presper Eckert and John W. Mauchly presented their solution to the problems in the form of the Electronic Numerical Integrator and Calculator (ENIAC) the world’s first electronic general-purpose digital computer.
The ENIAC, built under a contract with the Army’s Ballistic Research Laboratory, became a great success for Eckert and Mauchly, but even before it was completed, they were setting their sights on loftier targets. The primary drawback of the ENIAC was the great difficulty involved in programming it. Whenever the operators needed to instruct the machine to shift from one type of calculation to another, they had to reset a vast array of dials and switches, unplug and replug numerous cables, and make various other adjustments to the multiple pieces of hardware involved. Such a mode of operation was deemed acceptable for the ENIAC because, in computing firing tables, it would need reprogramming only occasionally. Yet if instructions could be stored in a machine’s memory, along with the data, such a machine would be able to handle a wide range of calculations with ease and efficiency.

The Turing Concept

The idea of a stored-program computer had first appeared in a paper published by English mathematician Alan Mathison Turing in 1937. In this paper, Turing described a hypothetical machine of quite simple design that could be used to solve a wide range of logical and mathematical problems. One significant aspect of this imaginary Turing machine was that the tape that would run through it would contain both information to be processed and instructions on how to process it. The tape would thus be a type of memory device, storing both the data and the program as sets of symbols that the machine could “read” and understand. Turing never attempted to construct this machine, and it was not until 1946 that he developed a design for an electronic stored-program computer, a prototype of which was built in 1950.
In the meantime, John von Neumann, a Hungarian American mathematician acquainted with Turing’s ideas, joined Eckert and Mauchly in 1944 and contributed to the design of ENIAC’s successor, the Electronic Discrete Variable Automatic Computer (EDVAC), another project financed by the Army. The EDVAC was the first computer designed to incorporate the concept of the stored program.
In March of 1946, Eckert and Mauchly, frustrated by a controversy over patent rights for the ENIAC, resigned from the Moore School. Several months later, they formed the Philadelphia-based Electronic Control Company on the strength of a contract from the National Bureau of Standards and the Census Bureau to build a much grander computer, the Universal Automatic Computer (UNIVAC). They thus abandoned the EDVAC project, which was finally completed by the Moore School in 1952, but they incorporated the main features of the EDVAC into the design of the UNIVAC.
Building the UNIVAC, however, proved to be much more involved and expensive than anticipated, and the funds provided by the original contract were inadequate. Eckert and Mauchly, therefore, took on several other smaller projects in an effort to raise funds. On October 9,1947, they signed a contract with the Northrop Corporation of Hawthorne, California, to produce a relatively small computer to be used in the guidance system of a top-secret missile called the Snark, which Northrop was building for the Air Force. This computer, the Binary Automatic Computer (BINAC), turned out to be Eckert and Mauchly’s first commercial sale and the first stored-program computer completed in the United States.
The BINAC was designed to be at least a preliminary version of a compact, airborne computer. It had two main processing units. These contained a total of fourteen hundred vacuum tubes, a drastic reduction from the eighteen thousand used in the ENIAC. There were also two memory units, as well as two power supplies, an input converter unit, and an input console, which used either a typewriter keyboard or an encoded magnetic tape (the first time such tape was used for computer input). Because of its dual processing, memory, and power units, the BINAC was actually two computers, each of which would continually check its results against those of the other in an effort to identify errors.
The BINAC became operational in August, 1949. Public demonstrations of the computer were held in Philadelphia from August 18 through August 20.


The design embodied in the BINAC is the real source of its significance. It demonstrated successfully the benefits of the dual processor design for minimizing errors, a feature adopted in many subsequent computers. It showed the suitability of magnetic tape as an input-output medium. Its most important new feature was its ability to store programs in its relatively spacious memory, the principle that Eckert, Mauchly, and von Neumann had originally designed into the EDVAC. In this respect, the BINAC was a direct descendant of the EDVAC.
In addition, the stored-program principle gave electronic computers new powers, quickness, and automatic control that, as they have continued to grow, have contributed immensely to the aura of intelligence often associated with their operation.
The BINAC successfully demonstrated some of these impressive new powers in August of 1949 to eager observers from a number of major American corporations. It helped to convince many influential leaders of the commercial segment of society of the promise of electronic computers. In doing so, the BINAC helped to ensure the further evolution of computers.
See also Apple II computer; BINAC computer; Colossus computer; ENIAC computer; IBM Model 1401 computer; Personal computer; Supercomputer; UNIVAC computer.

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