Currently available microcomputer development systems/tools become rather inefficient when employed to debug real-time malfunctions; that is, intermittent or even unrepeatable hardware/software malfunctions encountered in time-critical applications. A new debugging technique, namely the Action-replay Debugging Technique, is proposed which can efficiently deal with a large class of these malfunctions. The aim of the Action-replay Debugging Technique is to provide an environment which is suitable for real-time debugging. In particular, an identical processor to the target, or a simulator of it, is forced to re-execute, or Action-replay, repeatedly and at any desirable speed the exact program path which the target processor traversed during the original interaction wi th its real-time environment. During successive "Action-replays" the user can investigate the system's behaviour (including timing characteristics) without real-time constraints which normally exist in time-critical applications.