Synopsis: 

       sem_clear(sem_id)

Arguments:

       sem_id - The semaphore ID.

       

Description:   This function clears a semaphore that was previous set by the calling task.     If an attempt is made to slear a semephore that was not previously set by the calling task then a error message is generated and the function will return -3.

Returns:    0 if the semaphore was successfully cleared by the calling task,  -1 if an invalid semaphore ID is specified, -3 if the semaphore was not set by the calling task.