Introduction #

So far, we talked about CPU time and scheduling.
Now let’s talk about memory, which is just as important.

Every program needs memory to run.
It needs memory for:

• Code
• Variables
• Data structures
• Temporary values

But memory is limited, and many programs run at the same time.

Managing this memory is one of the core jobs of an operating system.

Why Memory Management Is Needed #

Imagine a system without memory management.

Programs would:

• Use any memory address they want
• Overwrite each other’s data
• Corrupt system memory
• Crash the whole system with one mistake

In early systems, this actually happened.

Modern operating systems exist to prevent this.

What the OS Does with Memory #

The operating system controls memory usage for all programs.

It decides:

• How much memory a program gets
• Where that memory is located
• Which memory belongs to which process
• When memory should be freed

A program never directly controls physical memory.
It always goes through the operating system.

Process Memory Isolation #

Each running process thinks it has its own memory space.

This is not accidental.

The OS makes sure:

• One process cannot read another process’s memory
• One process cannot overwrite system memory
• A crash in one process does not affect others

This isolation is critical for stability and security.

Logical vs Physical View (Basic Idea) #

From the program’s point of view:

• Memory looks continuous
• Addresses start from zero
• Everything looks simple

From the hardware’s point of view:

• Memory is physical
• Shared between all processes
• Limited in size

The operating system sits in between and maps what the program sees to real memory.

You don’t need to know the details yet.
Just remember that programs never see real physical memory directly.

Memory Allocation and Deallocation #

When a program runs, it:

• Requests memory
• Uses it
• Releases it when done

The operating system:

• Gives memory when available
• Tracks who owns it
• Reclaims it when the process exits

If this is not done properly:

• Memory leaks happen
• System performance degrades
• Eventually, programs fail to run

This is why memory management exists.

Why This Matters in Linux #

Linux systems often run:

• Many long-running processes
• Background services
• Servers that stay up for months

Without proper memory management:

• The system would slow down
• Processes would fail randomly
• Reboots would be frequent

Good memory management keeps Linux stable even under heavy load.

Summary #

Memory management is required because:

• Memory is limited
• Many programs run at the same time
• Programs must be isolated
• Crashes must be contained

The operating system:

• Controls memory allocation
• Protects memory between processes
• Hides physical memory details from programs

This overview is the base.
Later lessons will go deeper into paging, virtual memory, and MMU concepts.