Memory Management

This lesson covers memory management in depth, focusing on paging, segmentation, virtual memory and page replacement algorithms. The OCR H446 specification requires you to understand how the OS manages memory to allow multiple processes to run efficiently.

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Why Memory Management Matters

The OS must:

• Allocate memory to each process so it has space for its code, data and stack.
• Protect each process's memory from being accessed by other processes.
• Optimise memory usage so that as many processes as possible can run simultaneously.
• Handle situations where the total memory required by all running processes exceeds the physical RAM.

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Paging

How Paging Works

The OS divides virtual memory (the address space seen by each process) into fixed-size blocks called pages and divides physical RAM into fixed-size blocks called frames. Pages and frames are the same size (commonly 4 KB).

Virtual Memory (Process A)        Physical RAM (Frames)