Slides: Virtual Memory Wrap-Up

class: title
# Virtual Memory Wrap-Up
## CSC 213 – September 26, 2025

---
# Agenda for Today
1. Department Events
2. Upcoming Work
3. Hexadecimal Review
4. Address Translation on x86
5. Wrap Up

---
# Department Events

## CS Table: Open Source Software Supply-Chain Security
.indent[
  Tuesday, September 30th at noon in JRC 224C
]

## Flu Shot Clinic
.indent[
  October 2nd and 3rd from 9am–4pm in the Natatorium Lobby  
  Register with Hy-Vee at <https://tinyurl.com/f25-flu-shot>
]

*To receive 0.25% extra credit, send an email to let me know you attended no more than 48 hours after the event.*

---
class: section, blue
# Upcoming Work

---
# Malloc Lab

**Due:** Wednesday, October 8th by 11:59pm  
**Late Deadline:** Wednesday, October 15th by 11:59pm

## Questions?

---
class: section, blue
# Hexadecimal Review

---
class: section, gray
# Whiteboard: Hex Digits

---
# Hexadecimal Math
Consider two pointer values:
- `p = 0x7FF25310`
- `q = 0x7FF2430C`

1. Which pointer has a lower address?

2. If these pointers are the start and end of an array, how large is the array in bytes? *(Hint: the end of an array is a pointer just past the last byte.)*

3. How many bytes do you think an element of the array takes up?

---
# Pointer Alignment
Which of these pointers are aligned to multiples of 8 bytes?
What about 16 or 32 byte alignment?

1. `0x55500410`
2. `0xCA7F00D5`
3. `0x00400008`
4. `0x7FFD1040`
5. `0x64430CC0`
6. `0x1D2C3B4A`

---
class: section, blue
# Address Translation on x86

---
# Real Parameters for 32-bit x86
Let's consider how the basic paging scheme we discussed last time would work on a 32-bit x86 machine.
The design of x86 gives us two important parameters:

**Pointer Size:** 32 bits (four bytes)  
**Page Size:** 4096 bytes (4KB)

From those parameters, we can determine more information about the address space:

1. How large is an address space?
   In other words, how many bytes can we address with a 32-bit pointer?
   
2. How many pages make up an address space?

3. Let's assume a single entry in a page table takes up 4 bytes (32 bits).
   How large will one page table be?

---
class: section, gray
# Whiteboard: Multi-Level Page Tables

---
class: section, blue
# Wrap Up

---
# Reminders

## Lab
The malloc lab is due in just under two weeks.
Be sure to make some progress this weekend or early next week!

## Assignment
There is no assignment this week.

## Need Help?
My regular office hours schedule is now posted.
Don't forget about this weekend's mentor session on Sunday from 3–5pm.

## Reading

- **Interlude: Files and Directories** (OSTEP, Chapter 39)