Electronic Numerical Integrator And Computer, better known as ENIAC was the first multipurpose computer in history. There had existed a few computers prior to it, but all of these though had been built to perform a single task. The ENIAC was not programmable as we think of in today’s terms, but could be used to make general calculations. It was also the first computer to be able to perform the IF statement. Although it was not a complicated IF statement it was very useful. Another revolutionary trait of ENIAC is the fact that it was exceedingly faster than any of its predecessors. This was the most useful thing about it because any computer before it might take 40 hours to do a calculation it could do in less than a minute.

John Mauchly had a lot of interest in creating a calculating machine. However, his colleagues, who said that it could never happen, laughed at his theories. Eventually Mauchly would meet John Atanasoff who would show Mauchly his Atanasoff-Berry machine. It was a special purpose machine and was also very slow. This Machine might have helped inspire Mauchly to work harder on his computation machine since he now knew one existed and how it worked.

Mauchly wanted to learn more about the latest electronic devices and machines so he went to Penn University also know as Moore School. Consequently he was hired as a teacher as many of the existing professors had been called away for World War II. Here is where he met J. Presper Eckert, known as "undoubtedly the best electronics engineer in the Moore School". He was only in his early twenties, and Eckert was a graduate student at the school. Eckert and Mauchly had plenty of time to discus the electronic computing device Mauchly wished to create as they worked together. Eckert said that it was possible to do this. Eckert then produced a memo called "The Use of Vacuum Tube Devices in Calculating.” This memo eventually reached the military, who would decide to sponsor their research out of need for faster computation.

The Military was one of the main reasons that this project happened. Calculations were needed to find the trajectories for certain weapons, and the current calculators could not keep up with the demands. When they found out Eckert and Mauchly already had the idea and plans for an electronic calculating device but lacked the funds.

Captain Herman Goldstine realized this and was able to present the concept to his superiors. A proposal was submitted to the Ballistic Research Laboratory. Eckert and Mauchly kept on producing arguments to support their work. On June 5, 1942 an agreement was made and the computer was named Electronic Numerical Integrator And Computer. They worked on the project in secret. No papers were published and discussions were limited. The computer was never finished in time to help out with the war, but still became quite useful when it was finished.

The hardware of the computer consisted of twenty accumulators. Each contained ten decade counters, which could hold ten digits each. One of the problems encountered when developing the computer was creating a reliable decade counter. Four different decade counters were tested during the development of ENIAC. Each accumulator when they worked properly could store both positive and negative numbers up to ten billion.

Another problem that they had was with the vacuum tubes. They needed the vacuum tubes to carry information. Most vacuum tubes were not very dependable though. If there were 17,480 tubes operating at a rate of 100,000 pulses per second it was calculated there would be 1.8 billion chances of a failure occurring each and every second. Thus much testing went on to find dependable vacuum tubes. Eckert went through and tested and found out why each vacuum tube failed in order to find a way to increase the life of each tube. Even one small glitch could affect the calculations largely and render it useless. Much caution had to be taken in order to prevent any glitches when soldering to make sure the tubes were preserved perfectly.

The IF statements in ENIAC were not great, but did exist. They worked in a very simple way. If the digit that is transmitted from the digit terminal was not zero, a given branch would be triggered. If the digit was zero, the branch would remain un-triggered. It was simple but helpful. If you wanted to check if two numbers were equal or not it could be done, where as it couldn’t previously.

ENIAC also contained ten steppers which could be used for creating loops. Each stepper can be associated with and output port. The output port can be routed as input at looped as many times as desired. It actually was more complicated than that. Since I did not comprehend how they worked that well I will not attempt to explain it to you.

There were a total of twenty accumulators in ENIAC. This meant that it could store up to twenty ten-digit numbers. On top of the ten digits, each accumulator held a sign for whether the number was positive or negative. It also could perform addition. From the use of addition subtraction, multiplication, division and square roots were also possible. There was no central memory so storage was limited to these twenty slots.

The ENIAC was not programmable because it did not have a memory. Its creators wished to make it programmable but only would do so as the creation of the ENIAC would allow. When it was finished it was only programmable be means of switches, cables and pulses. It could not store more that what was in it accumulators. Execution was done by setting the switches manually then turning it on. In its later years, Dr. John von Neumann had developed a way to convert the digit pulses of ENIAC to programming pulses.

In 1946 is was disassembled and moved to Aberdeen Proving Ground in 1947 where it was reassembled. Its maintenance was difficult there as there were thousands of components to maintain. Research and testing was done on the vacuum tubes. This information led to vast improvements on vacuum tubes themselves.

Over its life ENIAC was used for many calculations. It served the Navy and Air Force by making computations for them. It made many of the calculations needed in the creation of the hydrogen bomb. A list of some of its other uses included weather prediction, atomic-energy calculations, cosmic-ray studies, thermal ignition, random-number studies, and wind-tunnel design, among other scientific studies. By about 1953 EDVAC and ORDVAC had both been created and were beginning to take some of the workload from ENIAC.

Dr. John von Neumann had his part in its upgrades. He suggested a way to leave the cables on the machine in place. They could then input data using switches. This saved a lot of time an also caused a lot less error. Other technologies that had been developed elsewhere were added to the machine. It was equipped with a new function-table selector, a special memory-address selector, and special pulse-shaping circuits. These all went along with the new memory that it had been given.

Eventually it was decided that the cost of operating ENIAC was far above its worth. The other computers could handle its workload and were much less expensive to operate. As it lost its usefulness at 11:45 p.m. on October 2, 1955, the power to ENIAC was removed. Efforts were made to preserve it by Dr. von Neumann. Some of its parts still exist in museums today.

Contrary to popular belief, ENIAC was not the first general-purpose computer. In 1973 the patent for ENIAC was invalidated by the Judge Earl Larson of the US District Court in Minneapolis. Larson found that ENIAC was based on the ideas of John Vincent Atanasoff, who constructed ABC, the first electronic computer, around 19401.

John Atanasoff was finally acknowledged as the true inventor of the electronic computer. However, ABC also wasn't the first general-purpose computer, because actually it wasn't general-purpose, as it wasn't programmable. It was hardwired for solving systems of linear equations2.

The real first ever digital programmable general-purpose electronic computer was built around the same time in Germany. In 1941 Konrad Zuse, a German engineer, built Z3, a binary computer, controlled by perforated strips of film. The machine was fully programmable and in fact it contained almost all features of a modern computer, as defined by John von Neumann in Preliminary Discussion of the Logical Design of an Electronical Computing Instrument (1946)3. The only exception was that the program was not stored in the internal memory of Z3, but on the perforated film strip. However, ENIAC also did not posess this ability - the programming was done by manually rewiring part of the computer.

Now let's give our due respect to Konrad Zuse4.

Sources (to back my claims):
1 http://www.computer.org/history/development/1973.htm
2 http://www.wikipedia.org/wiki/Atanasoff_Berry_Computer
3 http://www.epemag.com/zuse/part4a.htm
4 http://www.bionomics.org/text/resource/articles/ar_015.html

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