The paper describes two programs of a suite which is under development which enables the student to explore the behaviour of controlled and autonomous linear discrete time systems without the necessity to learn a simulation language. The first program, DCSS (Digital Control System Simulator), deals with the simulated behaviour of discrete systems with or without a variety of controllers. A wide range of default systems, up to fifth order with time delay, can be selected by single keystrokes; the range of inputs includes square wave, triangle wave, sinusoidal and repeated pulse signals and noise or constant offsets can be added. The second program, Filter, provides the user with a powerful digital filter design and simulation facility. Again, all options can be achieved with one or more keystrokes to select options from a menu. On starting the program, the user selects IIR or FIR filter structures, sets the clock rate and can then choose to design a filter, see the time response or see the frequency response. Consider, for the sake of brevity, the case of an MR filter. In the design sub-section, the user can specify the filter order, select Butterworth, Bessel, Chebyshev, Elliptic, Bessel or RC filters and lowpass, highpass, bandpass or bandstop characteristics. The programs are fully interactive and the user can interupt the program to alter the system, controller, set point or feedback configuration by single keystrokes.