This document discusses memory management in operating systems. It defines memory management as allocating RAM to user programs and reclaiming memory after programs finish. It also describes protecting each user's memory from other programs. The document discusses physical and virtual memory, and types of virtual memory including paged, segmented, and swapped memory. It defines static and dynamic memory allocation, with static allocation assigning fixed memory at compile time and dynamic allocation assigning variable memory as needed from the heap.

1. Memory Management
Operating System

2. What is Memory Management ?
RAM
User program
User program
Give memory to user program

3. What is Memory Management ?
RAM
Finished work
User program
Reclaim Memory after finish the
work

4. What is Memory Management ?
RAM
User 1 Task
USER 1 Task
User 2 Task
Protecting each user’s memory area
from other user programs
USER 2 Task

5. Requirements for Memory Management
★ Relocation
★ Protection
★ Sharing
★ Logical Organization
★ Physical Organization

6. What is Physical Memory ?
❏ Actual RAM of the system
❏ Also called Primary Memory
❏ Directly accessible by CPU
❏ Holds instruction of programs to
execute
RAM

7. What is Virtual Memory ?
❖ An imaginary memory area supported by some OS in conjunction with
the hardware.
❖ An alternate set of memory addresses.
❖ Programs use these virtual addresses rather than real addresses to
store instructions and data.
❖ The purpose of virtual memory is to enlarge the address space

8. Kinds of Virtual Memory
The Heap
Allocated Memory
Paged Memory
Segmented Memory
Physical Memory

9. What is Segmented Memory ?
❖ An address space logically divided into sections, called segments.
❖ A segment has a set of permissions, and a length, associated with it.
❖ Segmented Memory is the additional 64 KB of RAM for early
computers.
❖ But most operating systems today don't use a segmented memory
model, with the advent of paging.

10. What is Paged Memory ?
A technique used by virtual memory operating systems to help ensure that
the data you need is available as quickly as possible.

11. What is Swapping ?
❏ To replace pages or segments of data in memory.
❏ Swapping is a useful technique that enables a computer to execute
programs and manipulate data files larger than main memory.
❏ The operating system copies as much data as possible into main
memory, and leaves the rest on the disk.When the operating system
needs data from the disk, it exchanges a portion of data in main memory
with a portion of data on the disk.

12. Allocated Memory
RAM
User program
User program
Process is called
Memory Allocation

13. Types of Memory Allocation
Static Memory Allocation
Dynamic Memory Allocation

14. Static Memory Allocation
int num = 10
RAM
x = 10
Stack
Heap

15. Dynamic Memory Allocation
char records [ ] = “Large
Data”
RAM
Large data
pointer
Heap
Stack