1. shmget()
   1. returns shmid for Shared Memory Segment key
2. shmdt()
   1. deletes the data segment referenced by shmaddr
3. shmat()
   1. blends shmid'ed sm-segment (SMS) into current data segment of the current process
   2. shmflag
      1. to handle user permssions
4. shmctrl()
   1. offers a bunch of control wrenches for messages