The motivation, history, and basic concepts of user-oriented languages for digital simulation of continuous systems are presented. Reference is made to two illustrative programs, the IBM 1130 and SYSTEM/360 Continuous System Modeling Programs (CSMP). Both programs accept user-oriented input statements for constructing simulation models and controlling simulation runs. The 1130 CSMP also allows on-line interaction by the user. An engineer or scientist at the console can alter the model or change run conditions based on direct observation of simulation outputs. The SYSTEM/360 CSMP is intended for batch-mode operation. It has extended facilities for describing the model and for obtaining automatic program control of successive simulation runs.