What is the main drawback of Pure Segmentation compared to Pure Paging?
Option B is correct. Because segments are variable-sized, allocating and deallocating them over time leads to External Fragmentation in physical RAM.
What is a 'Page Fault' in Virtual Memory systems?
Option B is correct. A Page Fault occurs when a referenced page has its valid bit set to '0' (invalid/not in RAM), prompting the OS to fetch it from disk.
Which page replacement algorithm suffers from Belady's Anomaly (where increasing allocated physical frames can INCREASE page fault count)?
Option C is correct. Belady's Anomaly occurs in FIFO page replacement, where adding more memory frames leads to more page faults for certain access strings.
Which page replacement algorithm provides the theoretically MINIMUM page fault rate for any reference string, but cannot be implemented in general-purpose OS because it requires future knowledge?
Option A is correct. Optimal (OPT) replaces the page that will not be used for the longest period in the FUTURE. It serves as a theoretical benchmark.
What is 'Thrashing' in an operating system?
Option C is correct. Thrashing occurs when processes do not have enough frames, causing constant page faulting and continuous page swapping.