Slides: Swapping to Disk

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# Swapping to Disk
## CSC 213 – September 21, 2026

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# Agenda for Today
1. Department Events
2. Upcoming Work
3. Swapping
4. Wrap Up

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# Department Events

## CS Table: Digital Sovereignty
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  Tuesday, September 22nd at noon in JRC 224C
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## CS Picnic (RSVP Required)
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  Friday, September 25th at 5pm in Merrill Park East  
  RSVP today at <https://tinyurl.com/f26-cs-picnic>
]

## Flu and COVID Shot Clinic
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  October 1st and 2nd from 9am–4pm in the Harris Center  
  Register with Hy-Vee at <https://tinyurl.com/f26-flu-shot>
]

*To receive a token, send an email to let me know you attended no more than 48 hours after the event.*

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# Upcoming Work

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# Assignment 3: Archive Printer

**Due:** Monday, September 21st by 11:59pm  
**Late Deadline:** Wednesday, September 23rd at 10:00am

## Questions
**Should the `!<arch>` signature appear before each file header?**  
No, it is only at the beginning of the file.
That matches what you'll see if you look at the content of the test inputs included with the assignment.

**Do we have to use the `struct` approach described on the assignment page?**  
No, this is entirely optional.
You're welcome to skip it if it doesn't make sense.

**My code works locally, but not in the autograder. What could be wrong?**  
*We'll talk about some of the edge cases that could show up in the autograder tests but not the sample inputs.*

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# Virtual Memory Lab

**Due:** Wednesday, September 23rd by 11:59pm  
**Late Deadline:** Monday, September 28th by 11:59pm

## Questions
**My program seems to be stuck in an infinite loop of segfaults. What's wrong?**  
There are a couple possibilities:
1. The code in your segfault handler is causing a segfault
2. Your segfault handler isn't fixing the cause of the segfault before returning (e.g. you didn't make the read-only copy writable)

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# No Assignment This Week
We'll take a break from assignments this week.

## Grading Updates
You'll all receive full credit for this non-assignment assignment, so this has no impact on your grade in the course.
I also lowered the number of assignments required for each grade level, but this change is independent of our skipped assignment 4.

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# Swapping to Disk

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# Discussion: Swapping to Disk
**Questions for think, pair, share:**

1. What problems can the OS solve by moving data from memory to disk?

2. What new problems could be caused by swapping data from memory to disk?

3. How should the OS decide which page to move from memory to disk?
   Try to think of the best possible policy, ideally one that is actually possible to implement.

*Start by thinking of answers on your own. I will let you know when to start discussion.*

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# Whiteboard: Swapping to Disk

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# Reminders

## Upcoming Deadlines
- **Archive Printer:** due tonight, or Wednesday morning with a token
- **Virtual Memory Lab:** due Wednesday, or next Monday with a token

## Need help? Use your resources!
- Book an appointment during office hours
- Attend mentor office hours
- Review slides, readings, and other course resources
- Use tools like `gdb` and AddressSanitizer to catch and diagnose issues

## Reading

- **Review lab before class**
            
- **Free-Space Management** (OSTEP, Chapter 17)