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ENIAC: the “first” Electronic Computer

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ENIAC: the “first” Electronic Computer Chapter 3 ENIAC: The “first” electronic computer In 1941, a key inventor of the ENIAC machine, John Mauchly, was teaching physics in Ursinus College in Philadelphia. One day, he received an invitation from the Moore Engineering School, UPenn, asking him to nominate a student for a 10 week summer program aimed at math and physics students. He decided to enroll himself in the course. 1 ABC John, very much interested in electronic com- puting, already got into touch with John Atana- soff, a professor in Iowa State, who had come up with a prototype of a digital computer with the help of Clifford Barry, one of his students. This machine was later referred to as “ABC”, i.e., the “Atanasoff Barry Computer”. This machines was declared in 1973 by a US District Court to be the first electronic digital comput- ing device. 2 A bit more... Conceived in 1937 and successfully tested in 1942, ABC was designed only to solve systems of linear equations. Thus, it is not a general purpose machine. Moreover, its intermediate result storage mech- anism, a paper card writer/reader, was unreli- able. When inventor John Vincent Atanasoff left Iowa State for World War II assignments, work on the machine was discontinued. 3 A bit more... On the other hand, ABC pioneered important elements of modern computing, including bi- nary arithmetic and electronic switching ele- ments, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. It was thus designated an IEEE Milestone in 1990. Let’s check out how to use this machine to solve some simple equations as we did back in fifth/sixth grade. 4 The historic background The Pearl Harbor got hit on Dec. 7, 1941, and the War began. Many new weapons, includ- ing new “guns”, were developed and tested in the Army’s Aberdeen Proving Ground, 80 miles away in Maryland. For each new gun to hit its target, the Army needed a new table showing the distance a shell would travel for every firing angle between five degrees and nearly vertical. By the middle of 1942, Moore School hired over a room full of women mathematicians doing vital war work, calculating ballistic tables for the military. 5 Track calculation Assume that the gun sends out bullet at the speed of 150 ft/sec. To plot its trajectory, assume that the gun aims at 30 degrees, we go through the following steps: 1. break the initial velocity into its vertical and horizontal components. ◦ Vx = 150 × cos(30 ) = 130 ft/sec, ◦ Vy = 150 × sin(30 ) = 75 ft/sec. 2. Choose a value for time and calculate the horizontal distance at that time. For example, after one section, the bullet travels horizontally x = Vx × t = 130 ∗ 1 = 130 ft. 6 3. Similarly, after one second, it travels verti- cally 2 y = Vy × t − 0.5 × g × t = 75(1) − 0.5 ∗ 32.2 ∗ 12 = 58.9 ft, where g is the gravitational acceleration. 4. For each value on time, we can calculate such a point, and we can then collect all such points and draw the trajectory on a sheet of graph paper. As you can see, the concept and the calcu- lation of trajectory is quite technical, com- plicated, but purely mechanical. Thus, some powerful tool was needed. 7 What is available? The only available tools at that time were me- chanic desk calculators, and it took about 40 hours to calculate one trajectory, using such a desk calculator. Thus it took lots of time and lots of persons to complete this task. At that point, UPenn also had a “differential analyzer”, one of five in the whole world. It was about 20 feet long, a complicated but purely mechanical device. It took this beast about forty-five minutes to finish a trajectory calculation. Two people operated that machine eight hours a day, six days a week, no vacations, except July 4 and Christmas, during the entire war. 8 The big question Such a task, albeit important, is boring, labor intensive, slow, but highly mechanical, as it is just calculation based on known formulas. The question is certainly “Could we do it bet- ter and faster?” I bet you all know the answer now, which kicks off the computer age. History repeatedly shows us that “Need is the mother of all the inventions.” 9 ENIAC was the answer After seeing this differential analyzer in oper- ation, John Mauchly, as early as August of 1942, wrote a note to the other professors in the Moore School, proposing to build an elec- tronic computer that would do the work that the differential analyzer had been doing. In terms of processing speed, John estimated that, if he could get a computer to operate at 100,000 additions per second, it would take just 10 minutes or less to calculate a firing trajectory. 10 This is the beginning of ENIAC, namely, “Elec- tronic Numerical Integrator and Calculator”. Originally, John’s ideas was not well received, since people were very busy then, also thinking the war would be over quick, so why bother? But, when things got worse, more and bigger, John’s idea was taken up more seriously. Thus, it is this need for a more efficient tool to support the war effort that was crucial to get the ENIAC project funded. 11 It is not just talking Just as John Mauchly was a mathematician and physicist, another person, Presper Eckert was an electrical engineer. It is the work of this combination that eventually made it happen. They started the design by simulating the pro- cess where it was done by hand. Essentially, they used some electronic device to store the numbers in decimal, and carry out the four basic operations, to solve the differential equa- tions that defined the path of a shell from the gun to its target. 12 Sounds long, but... Although such a calculation would take mil- lions of operations, it would not take long when the machine was to operate at the speed of 100,000 operations per second. Mauchly figured it would take about five min- utes to find out one trajectory. 13 Money first Once the design was completed, the head of the Moore School went to the Army’s Ballistic Research Lab for the financial support. On April 8, 1943, they submitted a formal pro- posal, and a final contract was signed off on June 5, which authorized six months of re- search and development of a “electronic nu- merical integrator and computer”at the cost of $61,700. 14 It was huge When ENIAC was completed, it cost half a million, occupying a room 50 feet by 30, with 18,000 vacuum tubes, 70, 000 resistors, etc.. It also generated lots of heat and the cooling systems weighted a couple of tons. The following machine shows how the machine looked like. Let’s find out more about it. 15 The role played by women The ENIAC was not completed when the War ended. All the real computers, i.e., the hu- man calculators, got laid off then, except five, who were chosen to be trained as program- mers, again in 10 weeks. It is important to point out that women worked side by side with men, and were primarily re- sponsible for the daily running of ENIAC, which is so clear in the video clips. 16 The role played by women Female programmers also developed improve- ments to ENIAC, and were honored in 1997 by the Women in Technology Hall of Fame. It is thus really a pity to see so few female students are among us today in choosing CS as their majors. 17 Not impressive technically Technically speaking, ENIAC had no internal memory, so by programming, it really meant plugging in and pulling out cables to form dif- ferent circuitry in a switch panel. For example, to calculate a firing table for a particular gun, it would take days to rewire the machine. The following figure shows the wires and switch panels in ENIAC. Thus, at that time, programming was even more diffi- cult than what we are doing today. 18 What did it do? ENIAC was finally ready in November 1945, and its first problem was to test the feasibility of the hydrogen bomb, and its first run was deemed successful. It was then introduced to the public in Febru- ary, 1946, as a “thinking machine”. The inter- est for such a machine was intense and world- wide. The first order for an ENIAC came within 10 days from Moscow, which was not accepted. 19 What happened afterwards? Even as ENIAC was constructed, its creators, Mauchly and Eckert thought this machine was useless, being so big, and started to work on its sequel, which was based on the binary system. In such a system, every number is represented in two digits, 0 and 1, but not in 10 digits as we are used to, just as all the computers do. This transition makes the computer much more reliable and drastically cuts down the number of components that a computer contains, since we now only need two different parts, instead of ten. Although it is difficult for us to work with a bi- nary system, it fits right in with a digital com- puter. 20 What else? Such a successor would also come with an in- ternal memory to store the program and data, which makes programming much faster. The ENIAC creators also thought about the potential commercial use of a computer, which was very visionary at the moment.
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