Reprogramming ENIAC involved a hike (part 2)Even with 18,000 vacuum tubes, ENIAC could only hold 20 numbers at a time. However, thanks to the elimination of moving parts it ran much faster than the Mark I: a multiplication that required 6 seconds on the Mark I could be performed on ENIAC in 2.8 thousandths of a second. ENIAC's basic clock speed was 100,000 cycles per second. Today's home computers employ clock speeds of 1,000,000,000 cycles per second. Built with $500,000 from the U.S. Army, ENIAC's first task was to compute whether or not it was possible to build a hydrogen bomb (the atomic bomb was completed during the war and hence is older than ENIAC). The very first problem run on ENIAC required only 20 seconds and was checked against an answer obtained after forty hours of work with a mechanical calculator. After chewing on half a million punch cards for six weeks, ENIAC did humanity no favor when it declared the hydrogen bomb feasible. This first ENIAC program remains classified even today.
Once ENIAC was finished and proved worthy of the cost of its development, its designers set about to eliminate the obnoxious fact that reprogramming the computer required a physical modification of all the patch cords and switches. It took days to change ENIAC's program. Eckert and Mauchly's next teamed up with the mathematician John von Neumann to design EDVAC, which pioneered the stored program. Because he was the first to publish a description of this new computer, von Neumann is often wrongly credited with the realization that the program (that is, the sequence of computation steps) could be represented electronically just as the data was. But this major breakthrough can be found in Eckert's notes long before he ever started working with von Neumann. Eckert was no slouch: while in high school Eckert had scored the second highest math SAT score in the entire country.
After ENIAC and EDVAC came other computers with humorous names such as ILLIAC, JOHNNIAC, and, of course, MANIAC. ILLIAC was built at the University of Illinois at Champaign-Urbana, which is probably why the science fiction author Arthur C. Clarke chose to have the HAL computer of his famous book "2001: A Space Odyssey" born at Champaign-Urbana. Have you ever noticed that you can shift each of the letters of IBM backward by one alphabet position and get HAL?