What is the purpose of a page table in paging?

• A. Maps virtual pages to physical frames.
• B. Stores data in a particular page.
• C. Contains CPU instruction mappings.
• D. Tracks the number of swaps.

Answer: (A)

In paging, memory is divided into equal-sized pages and physical memory into frames. The page table serves as the lookup that tells the hardware which physical frame holds the data for each virtual page. Each entry corresponds to a virtual page and stores the frame number where that page currently lives, along with bits that indicate whether the page is in memory (valid), what kind of access is allowed (protection), and other status bits like dirty or referenced.

When the CPU generates a virtual address, it splits it into a page number and an offset. The page number is used to index the page table, which gives the frame number. That frame number, combined with the offset, produces the actual physical address. If the page isn’t currently in memory, a page fault will occur and the operating system will load it, updating the page table entry accordingly.

This mapping is what enables process isolation and efficient use of memory. The other options describe different kinds of storage or tracking, but they aren’t what the page table does: it doesn’t store data in a page, it doesn’t map CPU instructions, and it doesn’t track how many swaps have occurred.