1. In a data processing apparatus wherein a queue of representations of processes awaiting the occurrence of a particular kind of event are stored in a memory member of said system, wherein a data element in the form of a semaphore is held in the memory member of said system, said data element having a tally field representing depending on its value one of (a) the number of process representations in said queue and (b) the number of times said particular kind of event has occurred or the number of resources awaiting processes, said tally field being decremented by one when a process requests a resource and incremented by one when either an event occurs or a resource is awaiting processes and wherein said apparatus during the execution of a process executes instructions of a particular class, a system for selectively initializing the data element or returning the data element to a preloaded value depending upon semaphore type, comprising: retrieving means controlled by one of said instructions for retrieving said data element from the memory member; testing means for testing the tally field of the data element retrieved from the memory member and in response generating a first signal when said tally field represents the number of process representations in said queue and a second signal when said tally field represents either the number of times said particular kind of events has occurred or the number of resources awaiting processes; initializating means responsive to said second signal and controlled by said one instruction for changing the number represented by said tally field either to zero when the tally field represents the number of times said particular kind of event has occurred or to a preloaded zero or positive value when the tally field represents the number of resources awaiting processes; and control means responsive to said first signal and controlled by said one instruction for controlling said apparatus to cease execution of said one instruction and to commence executing a different instruction.