By Darwyn F. KelleyComputer Historian
What is the difference between a Computer and a Calculator? One the most satisfactory definition states, "An automatic computer is a machine that manipulates symbols in accordance with given rules in a predetermined and self-directed manner.."The most significant word here undoubtedly is "self directed". Any calculating device whether it be an abacus or an adding machine must be other-directed, that is, man directed.An automatic computer, however has the ability to accept data and then work upon that data according to a preset program without human intervention, although human beings must, of course, devise the program which controls the automatic manipulation of the data. Regardless whether the computer is one of the special-purpose types for solving engineering and scientific problems or a general-purpose computer manufactured in large quantities, the principle remains the same.How did computers come into being and why did anyone want to build one in the first place? Starting from crude methods of piling stones to represent numbers and proceeding hrough such ingenious devices as the abacus, he has long been in pursuit of improved calculating methods. He has always been limited however, by the state of technology in the times in which he lived. As long ago as the 1820's Charles Babbage, in England made a "difference engine"., which was sound in principle, but which unfortunately was very unreliable due to the availability of only crudely machined parts. The first true computer to be manufactured in any quantities was Ford Instrument Computer in 1915. A mechanical analog device. The Ford Computer was a marvel of gear trains, linkages, and differentials. It was difficult to keep in adjustment and very complicated to manufacture, but it did the job it was intended to do- find and keep the range for naval guns.In 1930, the first general-purpose computer was built at MIT under the direction of Dr. Vannever Bush. It to was a mechanical monster, but it could be disconnected and reconnected to solve different equations.All of these devices were analog. That is they operated on real inputs such as voltages or the rotation of gears and they produced real outputs, such as training of the guns of a main battery. Analog computers have both advantages and disadvantages. They produce almost instantaneous output, but since they act upon analogies to numbers rather than on numbers themselves, their output is never perfectly accurate. They can be used to train a gun but not to calculate a payroll.In 1939, a major breakthrough occurred when Dr. Howard Aiken of Harvard completed the basic plans for a sequential, digital, electromechanical computer. This computer was an unwieldy conglomeration of office calculating devices, but it embodied two important concepts. First, it operated on real numbers, rather than on analogs of numbers, and, second it had the ability to make decisions. That is, it could compare two numbers when a partial result had been obtained and then follow one of two paths for further computation, depending upon the result of the comparison. All computers operate on this principle today.Dr. Aiken's machine was still an electromechanical device and naturally was subject to failure through wear and tear and had such commonplace troubles as simply getting dirty. Also there were obvious physical limitation on the speeds which it could be operated.The next major breakthrough came in 1946, when the first all-electronic, digital sequential computer was delivered. It was many times faster and far more reliable than any mechanical computer could be. It was an invention of J. Presper Eckert and Dr. John Mauchly, who later formed a company which eventually became, the UNIVAC Division of Sperry Rand. The name of this first Electronic Computer was ENIAC. (Acronym for :Electronic Numeric Integrated Automatic Computer). It was the father of all modern electronic computers.Next, in rapid succession came BINAC, the first computer with serial logic; Univac I , the first commercial computer, the Univac 1103A, the first computer to use core storage, the Univac Solid State, the first all Solid State Computer to be offered commercially, The Univac LARC, the world's most powerful computer at that time.
The ENIAC computer, pictured above was installed ,at Aberdeen Proving Grounds , Aberdeen, Maryland. It weighed nearly 30 tons and occupied 15,000 square feet of floor space.ENIAC contained more than 19,000 vacuum tubes which were used to perform 5,000 additions per second. .As one might expect, making ENIAC function was a tedious task. Operators used plug boards and wires to program the desires operations and entered the numbers used in calculations by turning a series of dials until they corresponded to the correct digits.By today's standards, ENIAC was slow, but it was 60 times faster than the mechanical differential analyzer which it replaced and at that time this was a large advance. ENIAC led the computer field during the period 1949 through 1952 when it served as the main computer workhouse for the solution of scientific problems of the Nation. It was the major instrument for the computation of all ballistic tables for the U.S. Army and Air Force. As a Sperry Univac, Senior System Engineer, assigned to the Univac installation at the Aberdeen Proving Grounds in 1957. ENIAC was delivered to the Ballistics Research Laboratory, (BRL) in 1946, therefore I missed this installation but did have many discussions with the personnel that used to work on this first amazing computer. It actually was not used to solve "Knotty Nuclear Problems" , but actually computed firing tables for the White Sands missile range.BRL also had many firsts., EDVAC and ORDVAC Computers were very powerful military computers which replaced ENIAC. Around 1958/1959 BRL decided to build a very advanced Scientific Computer. BRLESC. (BRL Electronic Scientific Computer). This was a very expensive and powerful computer but it did contain vacuum tubes at the time when all commercial computers were switching to solid state devices. This computer was made obsolete by Solid State Technology.
BINAC
The next machine produced by the Eckert & Mauchly team was Binac, special-purpose computer, Only one was built. Binac embodied four important advances, however: it used serial instead of parallel logic; it was the first computer to be internally programmed; it was the first computer to use magnetic tape; and it was the first computer to use solid state elements. Internal programming eliminated the time-consuming and tedious task of changing a problem by connecting external cables.
In parallel-logic systems, if one wishes to add two 3 digit numbers, one provides three add circuits, one for each column. In a serial machine, the columns are added one at a time, sequentially. This arrangement eliminates many parts and, of course, when the number of parts goes down so does the cost.Binac's use of Magnetic tape was limited to small reels. Small as it was, however, this 2 inch reel was the forerunner of the complex tape input and storage systems.In part, Binac achieved the speed necessary to the successful operation of a serial machine by the use of crystal diodes instead of vacuum tubes for switches. All sequential machines really are giant switching networks. Vacuum tubes still were used for amplification, but this first use of crystal diodes, as long ago as 1948, foreshadowed today's all solid-state machines with their greatly increased speeds and greatly reduced size, power and cooling requirements, and costs. A solid state component uses the flow of electrons through a solid material.
After Binac, new developments came thick and fast. The memory utilized in Binac was mercury tank memory. The design of this storage device was based on the very simple fact that an electrical pulse could be converted to a sound pulse (by means of piezo-electric quartz crystal and that this sound crystal would travel at relative low speed through a body of mercury. When it came out the other end, it could be reconverted to an electrical pulse by another crystal, amplified, and sent back into the tank. The net result was that the "bit" of information kept circulating until such time until called for by the computers circuitry. Mercury Delay Memory was also utilized in the
One of the largest factors in the success of UNIVAC I was the revolutionary input-output equipment offered with it. All input to the computer and output from it was by means of magnetic tape. The magnetic tapes were prepared off-line by a Unityper and information from them was printed out (also offline) by a Uniprinter. A keyboard and a typewriter were also provided with UNIVAC I for getting information into and out of the computer, but these generally were used in the course of checking out programs and rarely during the actual computer run.The Uniservo I was for communication and intermediate storage between the input-output devices and the computer. The magnetic tape was recorded at 120 digits per inch and could move past the read-write heads at 100 inches per second. Since Mylar tape had not been invented and the other alternative was acetate film, (which was very unstable), Univac choose to use metallic tape. Uniservo used small tape reels because they each weighed 25 lbs, but were very reliable. Also vacuum buffering was not yet invented so the buffering technique was to use elaborate rubber bands.Before long, the Card-To-Tape Converter was added to the input-output array. It read punched cards and converted the data into pulses on magnetic tape ate the rate of 240 cards per minute. A single standard reel of tape could hold as many as 4000 punched cards. A new High Speed printer was introduced which read magnetic tape and printed at 600 lines per minute. Newer High-Speed Printers operated at about 720 lines per minute but technology at that time limited printer speeds to 720 line per minute.Improvement in Technology was an ongoing process. The Unityper II, occupied 2 cubic feet instead of 20. Besides costing less to begin width it costs less to maintain. Uniservo II tapes moved at the same speed as the Uniservo I tapes- 100 inches per second but they were effectively twice as fast because twice as much information was recorded per inch.
UNIVAC File Computer
Remington Rand, through its acquisitions of the Eckert-Mauchly Computer Corporation (EMCC) in February 1950 and Engineering Associates (ERA) in December 1951 became the leading (and for a brief time the only) computer vendor in the world. Remington Rand decided to market a medium -scale computer to be called the UNIVAC File Computer. As its name indicated the File Computer was intended to provide access to data files stores on magnetic drums. This was very unusual for that time. Most computers read in data records from punched cards, paper tape or magnetic tape, process them back out to cards or tape, but they had no provision for long term on-line storage of data. The original File Computer had a 1,070 word drum, a memory that had twelve 6-bit digits or characters per word. The computer performed decimal arithmetic on numbers represented in Excess-3(XS-3) code. In XS-3, each decimal digit was represented by a binary value three higher, that is, 0 by 000011, 1 by 000100, etc. There were also codes for letters and special characters, such as 0101100 for A, 010101 for B and so on. The 1070-word drum which had an average access time of 2.5 milliseconds, was for storage of data actually being worked on by the program. General storage data was provided by from one to ten 15,000 word drums, whose average access time was 17 milliseconds. It was possible to have a processor which did tape sorting and collating, separately from the central processor.Besides doing the usual sort of batch work, the File Computer could provide interactive access to the stored data via one to ten terminals, which were called "input-output devices", An input-output device consisted of an inquiry typewriter, a punched card unit(using either 80 or 90 column punched cards), a paper type unit, a printer, and an optional Magnetic Tape drive. The input-output devices could operate independently from the Central Processing complex and perform input-output operations while the processor was doing something else.The File Computer Model 1 was built in 1957. It has twenty words of core storage, a tiny amount, but enough to provide for some internal programming capability, It allowed for a combination of internal and plug board instructions in the same operation, There were 27 instructions in the internal instruction set, including the arithmetic, comparison, jumps, suppression of left zeros, test for input from I/O station, and transfer to the plug board. The plug board had 19 operations, one of which transfer of control to the program memory. The memory instructions were twelve-digits in length, the last three specified the instruction code, while the others comprised three three-digit storage addresses. A field upgrade was later available which replaced the main memory drum with 1740 words of core memory this upgrade increased the operating speed by a factor of 3.6.Eastern Airlines used a File Computer for their reservation system. In 1957 Eastern and the St. Paul engineering staff developed a terminal device, called an agent set, for use on the File Computer, which had a keyboard and push-button matrix for selection of the function to be performed. A demonstration of the agent set took place in August 1957, but the reservation system did not start running until September 1958. The system covered nine cities (Atlanta, Birmingham, Boston, Houston, New Orleans, New York-Newark, Philadelphia and Washington) and within two months was processing one transaction per second. Northwest Airlines started using this reservation system in November 1959 and Capitol Airlines followed in early 1960. Douglas Aircraft Company was the largest user of File Computers, with 7 installations. Other users of the File Computer included the C&P Telephone Co., Western Electric, Michigan Bell, First National City Bank, various Army and Marine Corp bases. (The photos above were taken by this writer in 1958 at Edgewood Army Chemical Center, Edgewood, Maryland)A series of development delays meant that the File Computers were delivered toward the end of the vacuum-tube generation of computer hardware. Transistor (second generation) computers began appearing in quantity in 1960 and 1961. These new Solid State computers made vacuum-tube computers such as the File Computer obsolete.
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