A.Users don’t need to be aware of the hardware architecture, the amount of memory and registers it has, or the port programming details.
B.The OS is on top of the hardware, and the application software runs on top of the OS.
C.The purpose of the OS is to show users the details of the processor registers, the flag bits and control bits, mode bits, etc.
D.Multiple applications use the software library provided by the OS for controlling the hardware.