Page replacement algorithms (FIFO, LRU, Optimal) in Operating Systems - Mini Project: Build & Apply

Understanding Page Replacement Algorithms: FIFO, LRU, and Optimal

📖 Scenario: You are learning how operating systems manage memory using page replacement algorithms. These algorithms decide which memory pages to remove when new pages need space.Imagine a small computer memory that can hold only a few pages at a time. When a new page is requested and memory is full, the system must replace one page using a specific strategy.

🎯 Goal: Build a simple step-by-step example showing how three page replacement algorithms (FIFO, LRU, Optimal) decide which page to replace when a new page is requested.You will create data structures to hold page requests, set up memory size, apply each algorithm's logic, and show the final memory state after processing requests.

📋 What You'll Learn

Create a list of page requests with exact values

Define the memory frame size as a variable

Implement the FIFO page replacement logic

Implement the LRU page replacement logic

Implement the Optimal page replacement logic

Show the final memory frames after processing all requests for each algorithm

💡 Why This Matters

🌍 Real World

Operating systems use page replacement algorithms to manage limited memory efficiently, improving computer performance.

💼 Career

Understanding these algorithms is important for roles in system programming, software development, and IT infrastructure management.

1

Set up the page request sequence

Create a list called page_requests with these exact page numbers in order: 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2

Operating Systems

# Create the list of page requests
# Your code here

Need a hint?

Use square brackets and commas to create the list with the exact numbers.

2

Define the memory frame size

Create a variable called frame_size and set it to the integer 3 to represent the number of pages memory can hold at once.

Operating Systems

page_requests = [7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2]
# Define the memory frame size
# Your code here

Need a hint?

Use a simple assignment to set frame_size to 3.

3

Implement FIFO page replacement logic

Write code to simulate the FIFO page replacement algorithm using the page_requests list and frame_size. Use a list called fifo_frames to hold pages in memory. For each page request, if the page is not in fifo_frames and memory is full, remove the oldest page (first in list) and add the new page at the end. If memory is not full, just add the new page. Use a for loop with variable page to process page_requests.

Operating Systems

page_requests = [7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2]
frame_size = 3
# Implement FIFO page replacement
# Your code here

Need a hint?

Use a list to hold frames and a loop to check each page. Remove the first page if full, then add the new page.

4

Implement LRU and Optimal page replacement logic and show final frames

Add code to simulate the LRU and Optimal page replacement algorithms using the same page_requests and frame_size. Create lists lru_frames and optimal_frames to hold pages. For LRU, replace the page that was least recently used when memory is full. For Optimal, replace the page that will not be used for the longest time in the future. Use for loops with variable i to track current position in page_requests. After processing all requests, the lists fifo_frames, lru_frames, and optimal_frames should show the final pages in memory for each algorithm.

Operating Systems

page_requests = [7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2]
frame_size = 3
fifo_frames = []
for page in page_requests:
    if page not in fifo_frames:
        if len(fifo_frames) == frame_size:
            fifo_frames.pop(0)
        fifo_frames.append(page)
# Implement LRU and Optimal page replacement
# Your code here

Need a hint?

For LRU, move recently used pages to the end of the list. For Optimal, check future requests to decide which page to replace.