Use of an algebraic language in laboratory control programming with small (4K) computers

Most lab-control programs for small (4K) computers must be written in assembly or machine language, making it necessary for the user to expend considerable time and effort both in learning assembly-programming skills and in writing programs. One of the most frequently used small laboratory computers (the PDP-8 series) can, however, be programmed to provide sophisticated control using an algebraic language (FOCAL) in as little as 4K memory locations. The FOCAL language includes a special program sequence, FNEW, which provides capacity for a single user-defined function written in machine language. This paper describes an implementation of the FNEW sequence that permits execution of multiple user-written machine language subprograms within a FOCAL program. Use of this capability in the context of process-control problems in the behavioral laboratory is discussed and illustrated.