ITPEC FE Subject A April 2025 Question 13
The relation between virtual address and physical address is shown below. Each virtual page and page frame starts at a multiple of 4096 and ends 4095 addresses higher. Virtual address space 4K-8K corresponds to 4096-8191 and 8K to 12K corresponds to 8192-12287. Which of the following is the physical address corresponding to the virtual address numbered 8300?
Explanation
24684 — find the virtual page, map it to its page frame, and keep the offset.
- •Page size: 4K = 4096
- •Virtual address 8300 lies in the page 8K–12K (8192–12287), which maps to page frame 6
- •Offset within the page: 8300 − 8192 = 108
- •Page frame 6 is 24K–28K and starts at 6 × 4096 = 24576
- •Physical address: 24576 + 108 = 24684
Answer (d)
Why not others:
- •(a) 8192 — the start of the virtual page 8K–12K, with neither translation nor offset
- •(b) 8300 — the virtual address itself, as if no translation took place
- •(c) 24576 — the start of page frame 6, forgetting to add the offset 108
Key rule: Paging replaces only the page number; the offset within the page carries over unchanged, so the physical address is the frame's start plus the offset.
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