Operating System. DCAP403

326 Pages·4.401 MB·English

by  Pooja Gupta

Operating System
DCAP403
Editor
Dr. Pooja Gupta
nil Sharma
www.lpude.in
DIRECTORATE OF DISTANCE EDUCATION
OPERATING SYSTEM
Edited By
Dr. Pooja Gupta
ISBN: 978-93-87034-83-9
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for
Lovely Professional University
Phagwara
CONTENTS
Unit 1: Introduction to Operating System 1
Sarabjit Kumar, Lovely Professional University
Unit 2: Operation and Function of Operating System 14
Pooja Gupta, Lovely Professional University
Unit 3: Operating System Structure 29
Deepak Mehta, Lovely Professional University
Unit 4: Process Management 48
Mithilesh Kumar Dubey, Lovely Professional University
Unit 5: Scheduling 70
Sahil Rampal, Lovely Professional University
Unit 6: Process Synchronization 96
Pooja Gupta, Lovely Professional University
Unit 7: Memory Management 119
Pawan Kumar, Lovely Professional University
Unit 8: File Management 139
Mithilesh Kumar Dubey, Lovely Professional University
Unit 9: I/O & Secondary Storage Structure 159
Ramandeep Kaur, Lovely Professional University
Unit 10: System Protection 182
Sarabjit Kumar, Lovely Professional University
Unit 11: System Security 200
Mandeep Kaur, Lovely Professional University
Unit 12: Security Solution 225
Ramandeep Kaur, Lovely Professional University
Unit 13: Case Study: Linux 241
Yadwinder Singh, Lovely Professional University
Unit 14: Windows 2000 300
Pooja Gupta, Lovely Professional University

SYLLABUS
Operating System
Objectives: In order to meet the ever increasing need of computers, study of operating system is compulsory. This is core
technology subject and the knowledge of which is absolutely essential for Computer Engineers. It familiarizes the students with
the concepts and functions of operating system. This subject provides knowledge to develop systems using advanced operating
system concepts.
(cid:122) To learn the evolution of Operating systems.
(cid:122) To study the operations performed by Operating System as a resource manager.
(cid:122) To study computer security issues and Operating System tools.
1. Introduction: Operating system Meaning, Supervisor & User mode, operating system operations & Functions, Types of
OS: Single-processor system, multiprogramming, Multiprocessing, Multitasking, Parallel, Distributed, RTOS etc.
2. Operating System Structure: OS Services, System Calls, System Programs, OS Structures, layered structure Virtual
machines,
3. Processes: Process Concept, PCB, Operation on Processes, Cooperating Processes, Inter process Communication,
Process Communication in Client Server Environment.
Threads: Concept of Thread, Kernel level & User level threads, Multithreading, Thread Libraries, Threading Issues
4. Scheduling: scheduling criteria, scheduling algorithms, Type of Scheduling: Long term, Short term & Medium term
scheduling, multi-processor scheduling algorithm, thread scheduling,
5. Process Synchronization: Critical Section problem, semaphores, monitors, Deadlock characterization, Handling of
deadlocks - deadlock prevention, avoidance, detection, recovery from deadlock.
6. Memory Management: Logical & Physical Address space, Swapping, Contiguous memory allocation, paging,
segmentation, Virtual memory, demand paging, Page replacement & Page Allocation algorithms, thrashing,
Performance issues
7. File Management: File concepts, access methods, directory structure, fi le system mounting, fi le sharing, protection,
Allocation methods, Free space Mgt., Directory Implementation.
8. I/O & Secondary Storage Structure: I/O H/W, Application I/O Interface, Kernel I/O subsystem, Disk Scheduling, disk
management, swap-space management, RAID structure.
9. System Protection: Goals of protection, Access matrix and its implementation, Access control and revocation of access
rights, capability-based systems
10. System Security: Security problem, program threats, system and network threats, cryptography as a security tools, user
authentication, implementing security defenses, fi rewalling to protect systems and networks.
Case studies Windows OS, Linux or any other OS

Sarabjit Kumar, Lovely Professional University Unit 1: Introduction to Operating System
Unit 1: Introduction to Operating System Notes
CONTENTS
Objectives
Introduction
1.1 Operating System: Meaning
1.2 History of Computer Operating Systems
1.3 Supervisor and User Mode
1.4 Goals of an Operating System
1.5 Generations of Operating Systems
1.5.1 0th Generation
1.5.2 First Generation (1951-1956)
1.5.3 Second Generation (1956-1964)
1.5.4 Third Generation (1964-1979)
1.5.5 Fourth Generation (1979 – Present)
1.6 Summary
1.7 Keywords
1.8 Self Assessment
1.9 Review Questions
1.10 Further Readings
Objectives
After studying this unit, you will be able to:
(cid:122) Defi ne operating system
(cid:122) Know supervisor and user mode
(cid:122) Explain various goals of an operating system
(cid:122) Describe generation of operating systems
Introduction
An Operating System (OS) is a collection of programs that acts as an interface between a user
of a computer and the computer hardware. The purpose of an operating system is to provide
an environment in which a user may execute the programs. Operating Systems are viewed as
resource managers. The main resource is the computer hardware in the form of processors,
storage, input/output devices, communication devices, and data. Some of the operating system
functions are: implementing the user interface, sharing hardware among users, allowing users
to share data among themselves, preventing users from interfering with one another, scheduling
resources among users, facilitating input/output, recovering from errors, accounting for resource
usage, facilitating parallel operations, organising data for secure and rapid access, and handling
network communications.
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Operating System
Notes 1.1 Operating System: Meaning
An operating system (sometimes abbreviated as “OS”) is the program that, after being initially
loaded into the computer by a boot program, manages all the other programs in a computer.
The other programs are called applications or application programs. The application programs
make use of the operating system by making requests for services through a defi ned Application
Program Interface (API). In addition, users can interact directly with the operating system
through a user interface such as a command language or a Graphical User Interface (GUI).
Figure 1.1: Operating System Interface
Hard Drive
Computer
Mouse Operating System
Monitor
Video Card
Sound Card
Keyboard Speakers
In a computer system, you fi nd four main components: the hardware, the operating system,
the application software and the users. In a computer system, the hardware provides the basic
computing resources. The applications programs defi ne the way in which these resources are
used to solve the computing problems of the users. The operating system controls and coordinates
the use of the hardware among the various systems programs and application programs for the
various users.
You can view an operating system as a resource allocator. A computer system has many resources
(hardware and software) that may be required to solve a problem: CPU time, memory space,
fi les storage space, input/output devices etc. The operating system acts as the manager of these
resources and allocates them to specifi c programs and users as necessary for their tasks. Since
there may be many, possibly confl icting, requests for resources, the operating system must decide
which requests are allocated resources to operate the computer system fairly and effi ciently.
An operating system is a control program. This program controls the execution of user programs
to prevent errors and improper use of the computer. Operating systems exist because: they are
a reasonable way to solve the problem of creating a usable computing system. The fundamental
goal of a computer system is to execute user programs and solve user problems.
While there is no universally agreed upon defi nition of the concept of an operating system, the
following is a reasonable starting point:
A computer’s operating system is a group of programs designed to serve two basic purposes:
1. To control the allocation and use of the computing system’s resources among the various
users and tasks, and
2. To provide an interface between the computer hardware and the programmer that simplifi es
and makes feasible the creation, coding, debugging, and maintenance of application
programs.
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Unit 1: Introduction to Operating System
An effective operating system should accomplish the following functions: Notes
1. Should act as a command interpreter by providing a user friendly environment.
2. Should facilitate communication with other users.
3. Facilitate the directory/fi le creation along with the security option.
4. Provide routines that handle the intricate details of I/O programming.
5. Provide access to compilers to translate programs from high-level languages to machine
language.
6. Provide a loader program to move the compiled program code to the computer’s memory
for execution.
7. Assure that when there are several active processes in the computer, each will get fair and
non-interfering access to the central processing unit for execution.
8. Take care of storage and device allocation.
9. Provide for long term storage of user information in the form of fi les.
10. Permit system resources to be shared among users when appropriate, and be protected
from unauthorised or mischievous intervention as necessary.
Figure 1.2: Abstract View of the Components of a Computer System
User 1 User 2 User 3 User n
Compiler Assembler Text editor Database
system
Application programs
Operating System
Computer hardware
Though systems programs such as editors and translators and the various utility programs (such
as sort and fi le transfer program) are not usually considered part of the operating system, the
operating system is responsible for providing access to these system resources.
The abstract view of the components of a computer system and the positioning of OS is shown
in the Figure 1.2.
Task “Operating system is a hardware or software”. Discuss.
1.2 History of Computer Operating Systems
Early computers lacked any form of operating system. The user had sole use of the machine and
would arrive armed with program and data, often on punched paper and tape. The program
would be loaded into the machine, and the machine would be set to work until the program
completed or crashed. Programs could generally be debugged via a front panel using switches
and lights. It is said that Alan Turing was a master of this on the early Manchester Mark I machine,
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