Multiprogramming the RCA 601

Abstract

Multiprogramming may be defined as the execution of several computer programs concurrently, under a time-sharing mode, with the aim of keeping all independently operable computer components continuously busy. The benefit to be derived from such a multiprogramming mode of operation then is to achieve maximum computer effectiveness. However, the running time required to achieve multiprogramming must be significantly less than the resultant gain in computer effectiveness. There are three cogent reasons why multiprogramming can enhance computer effectiveness. Since most programs are either compute limited or Input-Output limited rather than evenly divided, a mixture of programs is potentially better balanced than a single program. Secondly, as computer capability increases, programs to be operated do not necessarily increase in size. Hence~ these programs are inherently incapable of utilizing the full capacity of the computer, whereas a program mixture would be able to use all of the computer capacity. Thirdly, the nature of a particular problem or the ineptitude of a programmer may result in poor simultaneity within individual programs. Since multiprogramming permits another program to use this “dead time”, more efficient use of the computer is made and the requirements on programmer ability is significantly reduced.