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Questions and Answers
What does the present bit in a page table entry signify?
What does the present bit in a page table entry signify?
What happens when a page fault occurs?
What happens when a page fault occurs?
Which step is NOT part of handling a page fault?
Which step is NOT part of handling a page fault?
What does a truly invalid reference during a page fault lead to?
What does a truly invalid reference during a page fault lead to?
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What initiates a page fault interrupt?
What initiates a page fault interrupt?
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What is the primary purpose of demand paging in operating systems?
What is the primary purpose of demand paging in operating systems?
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During a page fault, which action is taken if the page is determined to be not in memory but not a reference error?
During a page fault, which action is taken if the page is determined to be not in memory but not a reference error?
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Which of the following best describes the role of the present bit in the page table?
Which of the following best describes the role of the present bit in the page table?
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What happens after the operating system copies the page from disk into a frame during a page fault?
What happens after the operating system copies the page from disk into a frame during a page fault?
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What would likely occur if the operating system detects a truly invalid reference during a page fault?
What would likely occur if the operating system detects a truly invalid reference during a page fault?
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Study Notes
Demand Paging
- Demand paging loads pages into memory only when needed, not at the start of execution.
- A "present bit" in the page table entry indicates whether the corresponding page is currently in memory.
- If a page is resident in memory, the entry points to the frame containing the page.
- A page fault is an interrupt when a program tries to access a non-resident page.
- The OS finds the page on disk, moves it to a frame, sets the present bit, and resumes execution.
Page Fault Handling
- A first access to a page triggers a page fault interrupt.
- The OS checks the page table:
- Invalid reference? Abort the program.
- Page not in memory?
- Find an empty frame.
- Read the page from disk into the frame.
- Update the page table (page/frame information).
- Set the present bit to 1.
- Restart the instruction causing the fault.
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Description
This quiz covers key concepts of demand paging and page fault handling within operating systems. It explains how pages are loaded into memory on demand and the steps involved when a page fault occurs, including the role of the OS in managing memory. Test your understanding of these critical components of virtual memory management.
