Operating System MCQs

Indexed access searches an index that maps keys or record numbers to data locations.
It combines fast lookup with the ability to traverse records in an indexed order.

The open-file table records kernel state needed while files are actively open.
Process file descriptors refer to these entries rather than duplicating all underlying information.

File locks can provide shared-read or exclusive-write coordination among processes.
They help preserve consistency when several users or programs access the same file.

Mapped I/O allows the page cache pages to appear directly in the process address space.
This can reduce system-call and data-copy overhead for suitable access patterns.

File attributes are metadata such as name, owner, size, type, timestamps, and permissions.
The other options are data contained within a file.

An instruction may span pages and access multiple operands, requiring several resident frames.
Too few frames could make correct execution or page-fault restart impossible.

Proportional allocation gives larger processes a larger share of the available frame pool.
The policy can be extended with minimums, maximums, or priority adjustments.

The working set estimates the process's current locality of active pages.
Keeping this set resident helps the process execute with a low page-fault rate.

During thrashing, frequent page faults cause heavy disk activity and little useful CPU execution.
Reducing multiprogramming or allocating more frames to active working sets can restore performance.

Memory mapping lets ordinary loads and stores reference file-backed virtual pages.
The operating system handles page faults, caching, and eventual write-back.

Prepaging attempts to reduce a burst of future page faults by fetching a cluster of likely useful pages.
If predictions are poor, unnecessary I/O and memory use can result.

A precise page fault occurs before the instruction successfully completes its required memory access.
Restarting the instruction preserves the same program behavior as if the page had already been present.