Operating System

1. Chapter (2)
Operating System Overview
Dr. Hnin Lai Nyo
Lecturer
Faculty of Computer Science

2. Lecture Contents
 Lecture 1: Operating System Objectives and Functions
 Lecture 2: The Evolution of Operating System
 Lecture 3: Major Achievements
 Lecture 4: Developments Leading to Modern Operating Systems
FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES

3. Lecture 3: Major Achievements
FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
 The Process
 Memory Management
 Information Protection and Security
 Scheduling and Resource Management

4. Learning Objectives
FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
 To know the major achievements in operating system
 To understand process management, memory management, information
protection and security, scheduling and resoruce management

5. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
 Four major theoretical advance in the development of OS:
 Processes
 Memory management
 Information protection and security
 Scheduling and resource management
Major Achievements in Operating Systems

6. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Processes
 A program in execution
 An instance of a program running on a computer
 The entity that can be assigned to and executed on a processor
 A unit of activity characterized by a single sequential thread of execution, a curent
state, and an assiciated set of system resources.

7. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Processes
Development of the Process
 Three major lines of computer system development created problems in timing
and synchronization that contributed to the development:
Multiprogramming
Batch Operation
 Processor is switched among the various programs residing
in main memory
Time Sharing  It is responsive to the individual user but be able to support many users simultaneously.
Real-time Transaction
Systems
 A number of users are entering queries or updates against a
database.

8. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Processes
Processes
Management
i
Context
Data
Program
(code)
Context
Data
Program
(code)
i
j
Process
list
Process
A
Process
B
b
h
Process index
PC
b
h
Base
limit
.
.
.
Other
registers
Main
memory
Processor
registers
Figure 2.8 Typical Process
Implementation

9. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
 The OS has five principle storage management responsibilities:
 Process isolation
 Automatic allocation and management
 Support of modular programming
 Protection and access control
 Long-term storage

10. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
 A facility that allows programs to address memory from a logical point of view,
without regard to the amount of main memory physically available.
 Conceived to meet the requirement of having multiple user jobs reside in main
memory concurrently.
 Allow processes to be comprised of a number of fixed size blocks, called pages.
 Program references a word by means of a virtual address (page no. + offset)
 Provides for a dynamic mapping between the virtual address used in the
program and a real address in main memory.
Virtual Memory
Paging

11. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
A1
A0 A2
A5
B0 B1 B2 B3
A7
A9
A8
B5 B6
Main
memory
User
program
A
User
program
B
Disk
Main memory consists of
a number of fixed-length
frames, each equal to the
size of a page. For a
program to execute, some
or all of its pages must be
in main memory.
Secondary memory
(Disk) can hold many
fixed-length pages. A
user program consists of
some number of pages.
Pages for all programs
plus the OS are on disk,
as are files.
Figure 2.9 Virtual Memory Concepts
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6

12. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
Figure 2.10 Virtual Memory Addressing
Virtual
address
Processor
Memory
management
unit
Main
memory
Secondary
memory
Real
address
Disk
address

13. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
Information Protection and Securtiy
 The nature of the threat that concerns an organization will vary greatly depending on the
circumstances.
 The problem involves controlling access to computer systems and the information stored in them.
 Much of the work in security and protection as it relates to OS can be roughly groupted into four
categories:
 Availability : protecting the system against interruption
 Confidentiality : Assures that the unauthorized users cannot read/access data
 Data integrity : Protection of data from unauthorized modification.
 Authenticity : the proper verfication of the identity of users and the validty of messages or data.

14. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Memory Management
Scheduling and Resource Management
 A key responsibility of an OS is managing resources.
 Any resource allocation and schedulig policy must consider three factors:
 All processes that are competing for the use of a particular resource to be equal and fair access.
 Fairness
 To discriminate among different classes of jobs with different service requirements.
 To make allocation and scheduling decisions to meet the total set of requirements
 Differential responsiveness
 The OS should attempt to maximize throughput, minimize response time and accomodate as many users as possible.
 Efficiency

15. FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
Summary
In this lecture, you learned about
 Three major lines of computer system development created problems in timing
and synchronization that contributed to the development.
 Five principal storage management responsibilities.
 Security and protection as it related to OS.
 Resource allocation and scheduling policy.

16. Learning Outcomes
FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
After the end of the lecture, the students will be able to:
 know the major theoretical advance in the development of operating
system.
 Understand memory management and resource allocation policies.

17. References
FACULTY OF COMPUTER SCIENCE, UNIVERSITY OF COMPUTER STUDIES
1. “Operating Systems, internal and Design Principles” by William
Stallings, 7th Edition, ISBN 13: 978-13-230998-1.