semaphore
Data structure provided by OS/2, and used for synchronization between threads and/or processes. OS/2 Version 2.0 allows mutex semaphores, event semaphores and muxwait semaphores. Semaphores may also be private (owned and accessible by a single process) or shared (accessible by all processes in the system). A process may create up to 65,535 private semaphores, and there may be a system-wide total of up to 65,535 shared semaphores in existence at any time.