Why was ENIAC needed and from where in the IT has come the word computer.

ENIAC(Electronic Numerical Integrator and Computer) is the crown of the american engineering in 1940’s, which was created for the military purposes, and its not so surprising, because in the middle of WWII US army required artillery firing ballistic tables. Those tables were needed to artillerists for more accurate shooting and took into account many parameters, which affected on the trajectory of the flight for the artillery shell. In 1943 The laboratory of the ballistic researches, where all the work for calculating the tables were done manually, were barely managing with always rising volume of those calculations. And then the representatives of this laboratory contacted Moore’s Electrotechnical school in University of Pennsylvania to count on that the scientists would help them to automatize the work of «Computers». «Computers» that was the name of the clerks, whose mission was to calculate those ballistic tables(i.e. compute). That’s why also ENIAC was called the computer - analogy with hundreds of men who made those computations manually. WWII made a great influence on the development of the informational technology, in particular on the ENIAC, despite the fact that ENIAC was finished and ready for work in 1945. Nevertheless, it was used to calculate ballistic tables, but the most important role ENIAC played in the creation of the more powerful weapon, than the accurate artillery attack - it was used for simulation of the thermonuclear explosion.

When ENIAC appeared, it was the very first digital computer which could calculate two ten-digit numbers in 0,0002 seconds - 50000 times faster than an average human, 20000 times faster than a calculator and 1500 times faster than Mark I, and for specialized purposes, it was even faster. Wherein scientists did not have right to make any mistakes and did not have unlimited amount of time. If that project did not achieve the required result, the development in this field would slow down for a long period of time. In common cases people build their prototypes, see their mistakes and start their work from the beginning. Because of the war ENIAC’s scientists had to make the machine which will work from the first launch. After rigorous analysis scientists gave preferences to the decimal system instead of binary and separated all system to modules, so it would be easier to operate with introducing and using the data. Each functioning module of the ENIAC was equipped with local program management schemes. Those schemes contained switches, which were used to install the required function, which module could process when it was accessed. When the result was obtained the operation passed to the next module in the operating sequence. The structure of ENIAC additionally included initialization module, a high speed multiplier, divider, square root module, and so on.(For example:High-speed multiplier worked in a similar way as it was done by a person using the integrated multiplication table. The process of multiplying two ten digit numbers took 2.6 milliseconds) It was very hard for the scientists to make those modules which contained 840 instruction program that used subroutine, nested loops and indirect addressing for both data locations and jump destinations. ENIAC had almost 18000 electronic lamps which consumed 174 kW, producing 100 kilohertz with amount of memory of 20 number-words and as John Presper Eckert(main constructor of the ENIAC) said, they had in disposition all electronic lamps which provider could give. Developers used 10 types of lamps (technically 4 types were enough, simply their total amount was not sufficient). It was made to reduce the crash probability. Theoretically ENIAC had lots of points of failure (1.8 billion failure options per second), because of which people thought that there is no option of use the machine practically. Eckert solved this problem by simply reducing the voltage served to the lamps(5.7 volts instead of 6.3). Nonetheless ENIAC was breaking not so frequently - one time per 20 hours. It’s not so much by today’s standards but for that time it was enough to make a monthly amount of work of mechanical calculators.

All these were made to simulate the problems that cannot be solved using traditional mathematics. Even after the calculations for the decay of nuclear fission, ENIAC continued running programs like weather simulations for seven more years. After this it was replaced with newer, more powerful computers. And now it can be found at the Fort Sill Field Artillery museum. It was made a great effort to collect the «puzzles» remained from the ENIAC and bring it back to working order.

The main problem of the ENIAC was that the program was actually stored in what we now call «read-only memory» or ROM, while the Manchester’s «Baby’s» program was stored in the same memory used for data. This drawback was that programming it was a complete nightmare. To change the program meant total rewiring of it with thousands of switches in wiring plugboards.

ENIAC was not exactly perfect computer, it was built from zero without any previous experience of creation of such devices. Despite its flaws, the lessons learned from ENIAC helped developers improve the next generation, including EDVAC, UNIVAC and Whirlwind, all of which improved upon programmability and memory storage. ENIAC was built only in one exemplar and engineering solutions, realized in ENIAC were not used in the next constructions of the computers. ENIAC is not the computer of the first generation, it was the computer of the generation «zero» . The true meaning of the ENIAC is in his existence, which proved that there is an opportunity of creation a fully electronic computer, which could work long enough to justify the cost for its construction and produce tangible results.

P.S Fun fact: To avoid the crash of the system or short circuit Eckert involved so called «mouse test». So they put all samples of wires into the cage with mice to see which isolation they did not like, and used only those wires which passed the «mouse test»

Reference

1. History of Eniac (https://habrahabr.ru/company/1cloud/blog/301918/)
2. Programming the ENIAC: an example of why computer history is hard (http://www.computerhistory.org/atchm/programming-the-eniac-an-example-of-why-computer-history-is-hard/)
3. Trajectory calculation (http://zuse-z1.zib.de/simulations/eniac/history.html)