GATE CS 2021 Set 1 Q11 — Memory Management and Virtual Memory

Let us analyze each statement individually to determine its correctness:

• Statement A: Paging helps solve the issue of external fragmentation (Correct)
  In paging, physical memory is divided into fixed-size blocks called frames, and logical memory is divided into blocks of the same size called pages. Since any page of a process can be mapped to any available physical frame, physical memory does not need to be contiguous. This completely eliminates external fragmentation.


• Statement B: Page size has no impact on internal fragmentation (Incorrect)
  Internal fragmentation occurs when a process does not fully occupy its last allocated page. On average, the internal fragmentation per process is estimated to be half of the page size ($\frac{S}{2}$, where $S$ is the page size). Therefore, larger page sizes lead to greater internal fragmentation, meaning page size directly impacts it.


• Statement C: Paging incurs memory overheads (Correct)
  To translate logical addresses to physical addresses, the operating system must maintain a page table for each process. These page tables reside in physical memory and consume space, thereby introducing memory overhead.


• Statement D: Multi-level paging is necessary to support pages of different sizes (Incorrect)
  The primary purpose of multi-level paging is to avoid keeping the entire page table of a process contiguously in main memory, thereby reducing the memory overhead for large virtual address spaces. It is not a mechanism required to support pages of different sizes.

Thus, the correct statements are A and C.