storing all instruction programs together with data in the same memory unit, so that, when needed, instructions could be changed in the same way as data. As a result of these techniques, computing and programming became much faster, more flexible, and more efficient with work. Regularly used subroutines did not have to be reprogrammed for each new program, but could be kept in "libraries" and read into memory only when needed. Hence, much of a given program could be created from the subroutine library. The computer memory became the collection site in which all parts of a long computation were kept, worked on piece by piece, and put together to form the final results. When the advantage of these techniques became clear, they became a standard practice. The first generation of modern programmed electronic computers to take advantage of these improvements was built 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 tape I/O devices. Physically, they were much smaller than ENIAC. Some were about the size of a grand piano and used only 2,500 electron tubes, a lot less then required by the earlier ENIAC. The first-generation stored-program computers needed a lot of maintenance, reached probably about 70 to 80% reliability of operation (ROO) and were used for 8 to 12 years. This group of computers included EDVAC and UNIVAC, the first commercially available computers. Early in the 50’s two important engineering discoveries changed the image of the electronic-computer field, from one of fast but unreliable hardware to an image of relatively high reliability and even more capability. These discoveries were the magnetic core ...
