ions too difficult to solve in any other way were evaluated with such machines. During both world wars, mechanical and, later, electrical analog computing systems were used as torpedo course predictors in submarines and as bombsight controllers in aircraft. Another system was designed to predict spring floods in the Mississippi River Basin. In the 1940s, Howard Aiken, a Harvard University mathematician, created what is usually considered the first digital computer. This machine was constructed from mechanical adding machine parts. The instruction sequence to be used to solve a problem was fed into the machine on a roll of punched paper tape, rather than being stored in the computer. In 1945, however, a computer with program storage was built, based on the concepts of the Hungarian-American mathematician John von Neumann. The instructions were stored within a so-called memory, freeing the computer from the speed limitations of the paper tape reader during execution and permitting problems to be solved without rewiring the computer. III. EARLY PROGRESS The rapidly advancing field of electronics led to construction of the first general-purpose all-electronic computer in 1946 at the University of Pennsylvania by the American engineer John Presper Eckert, Jr. and the American physicist John William Mauchly. Called ENIAC, for Electronic Numerical Integrator And Computer, the device contained 18,000 vacuum tubes and had a speed of several hundred multiplications per minute. Its program was wired into the processor and had to be manually altered. The use of the transistor in computers in the late 1950s marked the advent of smaller, faster, and more versatile logical elements than were possible with vacuum- tube machines. Because transistors use much less power and have a much longer life, this development alone was responsible for the improved machines called second-generation computers. Components became smaller, as did inter-component spacing...
