d. Thus, much of a given program could be assembled from the subroutine library. The all-purpose computer memory became the assembly place in which parts of a long computation were stored, worked on piecewise, and assembled to form the final results. The computer control served as an errand runner for the overall process. As soon as the advantages of these techniques became clear, the techniques became standard practice.The first generation of modern programmed electronic computers to take advantage of these improvements appeared in 1947. This group included computers using random access memory (RAM), which is a memory designed to give almost constant access to any particular piece of information. These machines had punched card or punched-tape input and output devices and RAMs of 1,000-word capacity with an access time of 0.5 microseconds (0.5? 10 sec); some of them could perform multiplications in 2 to 4 microseconds. Physically, they were much more compact than ENIAC: some were about the size of a grand piano and required 2,500 small electron tubes, far fewer than required by the earlier machines. The first-generation stored-program computers required considerable maintenance, attained perhaps 70% to 80% reliable operation, and were used for 8 to 12 years. Typically, they were programmed directly in machine language, although by the mid-1950s progress had been made in aspects of advanced programming. These machines included EDVAC and UNIVAC, the first commercially available computers. Advances in the 1950sEarly in the 1950s two important engineering discoveries changed the image of the field, from one of fast but often unreliable hardware to an image of relatively high reliability and even greater capability. These discoveries were the magnetic-core memory and the transistor-circuit element.These new technical discoveries rapidly found their way into new models of digital computers; RAM capacities increased from 8,000 to 64,000 wor...
