Communications of the ACM

h show the execution characteristics of two types of commonly used programs in a large-scale, time-shared computer system. A software monitoring facility built into the supervisor was used for data collection during normal system operation. These data were analyzed, and results of this analysis are presented for a Fortran compiler and an interactive line file editor. Probability distribution functions and other data are given for such things as CPU intervals, I/O intervals, and the number of such intervals during execution. Empirical distributions are compared with simple theoretical distributions (exponential, hyperexponential, and geometric). Other data show paging characteristics of tasks as a function of the number of pages those tasks have in core.