Int 15 Fn 01  - Multidos Plus - Request Resource Semaphore                 [T]

   AH = 01h
   AL = semaphore number (00h-3Fh)

Return: AH = status
       00h successful
       02h invalid semaphore number

Notes: if the semaphore is not owned, ownership is assigned to the calling
     task and the call returns immediately
   if the semaphore is already owned by another task, the calling task
     is placed on a queue for the semaphore and suspended until it can
     become owner of the semaphore
   semaphore 0 is used internally by MultiDOS to synchronize DOS access

See Also: AH=02h"MultiDOS",AH=10h"MultiDOS",AH=1Bh"MultiDOS"