undertook (1945) a theoretical study of computation that demonstrated that a computer could have a very simple, fixed physical structure and yet be able to execute any kind of computation effectively by means of proper programmed control without the need for any changes in hardware. Von Neumann contributed a new understanding of how practical fast computers should be organized and built; these ideas, often referred to as the stored-program technique, became fundamental for future generations of high-speed digital computers.The stored-program technique involves many features of computer design and function besides the one named; in combination, these features make very-high-speed operation feasible. Details cannot be given here, but considering what 1,000 arithmetic operations per second imply may provide a glimpse. If each instruction in a job program were used only once in consecutive order, no human programmer could generate enough instructions to keep the computer busy. Arrangements must be made, therefore, for parts of the job program called subroutines to be used repeatedly in a manner that depends on how the computation progresses. Also, it would clearly be helpful if instructions could be altered as needed during a computation to make them behave differently. Von Neumann met these two needs by providing a special type of machine instruction called conditional control transfer who permitted the program sequence to be interrupted and reinitiated at any point and by storing all instruction programs together with data in the same memory unit, so that, when desired, instructions could be arithmetically modified in the same way as data.Computing and programming became faster, more flexible, and more efficient, with the instructions in subroutines performing far more computational work. Frequently used subroutines did not have to be reprogrammed for each new problem but could be kept intact in "libraries" and read into memory when neede...
