SSC IMD SA 2017 – Question 143

Which of the following is used as an index into the page table?

• Frame bit
• Page number
• Page offset
• Frame offset

Detailed Explanation:

The correct answer is b) Page number (पृष्ठ संख्या).

In paged memory management, the CPU generates a logical address that is split by the hardware into two distinct parts:

• Page Number ($p$): Serves as an index into the process’s page table. The page table contains the base physical address of each frame in physical memory.
• Page Offset ($d$): Defines the specific byte/word displacement within the page. Combined with the frame base address, it yields the physical memory address:$$\text{Physical Address} = (\text{Frame Number} \times \text{Page Size}) + \text{Offset}$$

Step-by-step translation:

1. CPU extracts the page number $p$.
2. Hardware uses $p$ as an array index to access entry $p$ in the page table.
3. The frame number $f$ is retrieved from that entry.
4. $f$ is concatenated with offset $d$ to form the physical address.