Writing Simulations in CSL

The word "simulation" is used in many contexts and has become one of the more confusing terms in the computer field. For example, it is used in the simulation of the order code of one computer on another, in the simulation of aircraft or guided weapon control systems by analogue computers, and in operational research. It is the latter use which is implied in the title and for which CSL is designed. The first version of CSL (Control and Simulation Language) was designed as a joint project by IBM United Kingdom Ltd. and Esso Petroleum Co. Ltd. (Buxton and Laski, 1962; CSL Reference Manual, 1962). Its initial applications were to the solution of problems in operational research connected with the control of industrial organizations. These problems were solved by simulation; that is, by writing in CSL a program purporting to imitate the working industrial system, and then studying the effect of changes in the methods of control of the system by manipulating the imitation program. The basic premise behind this approach is that it is cheaper and less disastrous to experiment with a computer program than to experiment with the reallife system of which that program is an imitation. Furthermore, it may be impossible to experiment on the real system if, for example, it does not yet exist.