Operating System (OS)
System maintenance:

always requires several programs
is not required if the system is well written
is usually not necessary
None of these
is necessary on all systems, regardless of how good

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Operating System (OS)
The Memory Buffer Register (MBR)

contains the address of the memory location that is to be read from or stored into.
is a group of electrical circuits (hardware), that performs the intent of instructions fetched from memory.
None of these
is a hardware memory device which denotes the location of the current instruction being executed.
contains a copy of the designated memory location specified by the MAR after a "read" or the new contents of the memory prior to a "write".

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