Transitions and time-sharing

It is argued that there is considerable confusion surrounding the use of terms that describe transitions between behaviours. After an attempt to clarify this issue, the concept of time-sharing is examined. It is concluded that interruption experiments are not relevant to time-sharing as originally defined. The functional significance of time-sharing is also considered. Previous attempts to suggest functions for time-sharing are shown to be incorrect. If time-sharing is to make functional sense, there must in general be some asymmetry in the costs and benefits of the activities involved.