Design of a PDP 11/40 simulator

This paper describes a PDP 11/40 simulator written in ALGOL W. The simulator imitates an 11/40 with 4K, a console I/O device, and a rudimentary operating system. The design allows an operator to sit at a remote terminal and perform the same functions that could be performed at the console of an 11/40. Fixed point instructions, traps, interrupts, illegal operation handling, and front panel switch control are implemented. The operating system monitors program execution, provides disk I/O, and establishes the environment in which the program operates. A powerful trace feature prints selected information during program simulation.ALGOL W provides a means to implement a well structured simulator to which additional features and experimental instructions are easily added. The simulator provides an environment where educational, experimental, and debugging work may be readily accomplished.