The invention: The first general-purpose electronic digital computer.
The people behind the invention:
John Presper Eckert (1919-1995), an electrical engineer John William Mauchly (1907-1980), a physicist, engineer, and professor
John von Neumann (1903-1957), a Hungarian American
mathematician, physicist, and logician Herman Heine Goldstine (1913- ), an army mathematician Arthur Walter Burks (1915- ), a philosopher, engineer, and professor
John Vincent Atanasoff (1903-1995), a mathematician and physicist
A Technological Revolution
The Electronic Numerical Integrator and Calculator (ENIAC) was the first general-purpose electronic digital computer. By demonstrating the feasibility and value of electronic digital computation, it initiated the computer revolution. The ENIAC was developed during World War II (1939-1945) at the Moore School of Electrical Engineering by a team headed by John William Mauchly and John Pres-per Eckert, who were working on behalf of the U.S. Ordnance Ballistic Research Laboratory (BRL) at the Aberdeen Proving Ground in Maryland. Early in the war, the BRL’s need to generate ballistic firing tables already far outstripped the combined abilities of the available differential analyzers and teams of human computers.
In 1941, Mauchly had seen the special-purpose electronic computer developed by John Vincent Atanasoff to solve sets of linear equations. Atanasoff’s computer was severely limited in scope and was never fully completed. The functioning prototype, however, helped convince Mauchly of the feasibility of electronic digital computation and so led to Mauchly’s formal proposal in April, 1943, to develop the general-purpose ENIAC. The BRL, in desperate need of computational help, agreed to fund the project, with Lieutenant
Herman Heine Goldstine overseeing it for the U.S. Army.
This first substantial electronic computer was designed, built, and debugged within two and one-half years. Even given the highly talented team, it could be done only by taking as few design risks as possible. The ENIAC ended up as an electronic version of prior computers: Its functional organization was similar to that of the differential analyzer, while it was programmed via a plugboard (which was something like a telephone switchboard), much like the earlier electromechanical calculators made by the International Business Machines (IBM) Corporation. Another consequence was that the internal representation of numbers was decimal rather than the now-standard binary, since the familiar electromechanical computers used decimal digits.
Although the ENIAC was completed only after the end of the war, it was used primarily for military purposes. In fact, the first production run on the system was a two-month calculation needed for the design of the hydrogen bomb. John von Neumann, working as a consultant to both the Los Alamos Scientific Laboratory and the ENIAC project, arranged for the production run immediately prior to ENIAC’s formal dedication in 1946.
A Very Fast Machine
The ENIAC was an impressive machine: It contained 18,000 vacuum tubes, weighed 27 metric tons, and occupied a large room. The final cost to the U.S. Army was about $486,000. For this price, the army received a machine that computed up to a thousand times faster than its electromechanical precursors; for example, addition and subtraction required only 200 microseconds (200 millionths of a second). At its dedication ceremony, the ENIAC was fast enough to calculate a fired shell’s trajectory faster than the shell itself took to reach its target.
The machine also was much more complex than any predecessor and employed a risky new technology in vacuum tubes; this caused much concern about its potential reliability. In response to this concern, Eckert, the lead engineer, imposed strict safety factors on all components, requiring the design to use components at a level well below the manufacturers’ specified limits. The result was a machine that ran for as long as three days without a hardware malfunction.
Programming the ENIAC was effected by setting switches and physically connecting accumulators, function tables (a kind of manually set read-only memory), and control units. Connections were made via cables running between plugboards. This was a laborious and error-prone process, often requiring a one-day set time.
The team recognized this problem, and in early 1945, Eckert, Mauchly, and Neumann worked on the design of a new machine. Their basic idea was to treat both program and data in the same way, and in particular to store them in the same high-speed memory; in other words, they planned to produce a stored-program computer. Neumann described and explained this design in his “First Draft of a Report on the EDVAC” (EDVAC is an acronym for Electronic Discrete Variable Automatic Computer). In his report, Neumann contributed new design techniques and provided the first general, comprehensive description of the stored-program architecture.
After the delivery of the ENIAC, Neumann suggested that it could be wired up so that a set of instructions would be permanently available and could be selected by entries in the function tables. Engineers implemented the idea, providing sixty instructions that could be invoked from the programs stored into the function tables. Despite slowing down the computer’s calculations, this technique was so superior to plugboard programming that it was used exclusively thereafter. In this way, the ENIAC was converted into a kind of primitive stored-program computer.
Impact
The ENIAC’s electronic speed and the stored-program design of the EDVAC posed a serious engineering challenge: to produce a computer memory that would be large, inexpensive, and fast. Without such fast memories, the electronic control logic would spend most of its time idling. Vacuum tubes themselves (used in the control) were not an effective answer because of their large power requirements and heat generation.
The EDVAC design draft proposed using mercury delay lines, which had been used earlier in radars. These delay lines converted an electronic signal into a slower acoustic signal in a mercury solu-
tion; for continuous storage, the signal picked up at the other end was regenerated and sent back into the mercury. Maurice Vincent Wilkes at the University of Cambridge was the first to complete such a system, in May, 1949. One month earlier, Frederick Calland Williams and Tom Kilburn at Manchester University had brought their prototype computer into operation, which used cathode-ray tubes (CRTs) for its main storage. Thus, England took an early lead in developing computing systems, largely because of a more immediate practical design approach.
In the meantime, Eckert and Mauchly formed the Electronic Control Company (later the Eckert-Mauchly Computer Corporation). They produced the Binary Automatic Computer (BINAC) in 1949 and the Universal Automatic Computer (UNIVAC) I in 1951; both machines used mercury storage.
The memory problem that the ENIAC introduced was finally resolved with the invention of the magnetic core in the early 1950′s. Core memory was installed on the ENIAC and soon on all new machines. The ENIAC continued in operation until October, 1955, when parts of it were retired to the sonian Institution. The ENIAC proved the viability of digital electronics and led directly to the development of stored-program computers. Its impact can be seen in every modern digital computer.
See also Apple II computer; BINAC computer; Colossus computer; IBM Model 1401 computer; Personal computer; Supercomputer; UNIVAC computer.
