Operating System MCQs

SCAN behaves like an elevator, processing requests along the current sweep before reversing.
This offers more predictable waiting than repeatedly selecting only the nearest request.

C-SCAN treats the cylinders as a circular queue and provides a more uniform wait across locations.
The return movement resets the sweep rather than servicing requests in the opposite direction.

A dedicated swap partition can be managed directly with policies optimized for paging traffic.
A swap file is more flexible, but it may involve additional file-system mapping overhead.

A protection domain defines the current authority of a subject over system objects.
Changing domains can change the operations the subject is permitted to perform.

Rows commonly represent subjects or domains, columns represent objects, and entries contain access rights.
Access-control lists and capability lists are practical ways to store parts of this conceptual matrix.

A hypervisor multiplexes physical CPU, memory, storage, and devices among virtual machines.
It also enforces isolation between guests and controls privileged operations.

Least privilege limits the damage possible from mistakes, compromised software, or abused credentials.
Permissions should be minimal in scope and duration while still allowing the required work.

Indexed allocation centralizes the addresses of a file's data blocks in an index structure.
This supports direct access without requiring physically adjacent blocks.

A bitmap provides a compact, indexable representation of free and used blocks.
It also makes finding contiguous runs possible through bit scanning.

A free list chains available blocks so allocation can remove blocks from the list and deallocation can return them.
Finding large contiguous runs may be less efficient than with a bitmap.

Seek time is the mechanical movement time needed to position the disk arm over the desired cylinder.
Rotational latency then waits for the desired sector to rotate under the head.

FCFS disk scheduling preserves request order and is simple and fair by arrival time.
It may produce large head movements when successive requests are far apart.