II Year B.Sc. Computer Science-Major
Revised Syllabus Under CBCS W.E.F. 2023-2024
III-SEMESTER: Course 8: OPERATING SYSTEM (OS)
SRI VENKATESWARA UNIVERSITY, TIRUPATI.
UNIT – I
Introduction to Operating System
(Q) What is Operating System?
Introduction:
An Operating System acts as an intermediary between the user of a computer and computer
hardware. The purpose of an Operating System is to provide an environment in which a user can execute
programs conveniently and efficiently.
An Operating System is software that manages computer hardware. The hardware must provide
appropriate mechanisms to ensure the correct operation of the computer system and to prevent user
programs from interfering with the proper operation of the system.
Definition of Operating System:
An Operating System is define as a set of programs that are used to control various resources of a
computer system to provide efficient sharing of resources among various application programs that are
executed by various users.
(OR)
An Operating System is a program that controls the execution of application programs and acts as an
interface between the user and the computer hardware. From system point of view, the Operating System
acts as:
Resource Allocator: To allocate various resources to the programs.
Manager: To manage all the resources.
Controller: To control the all the activities of I/O devices and user programs.
Control Program: To manage the execution of user programs.
Examples of Operating System are MS-Windows (Windows Xp, Windows 2003 Server, Windows Vista,
Windows 7, Windows 8, Windows 10, and Windows 11), Linux, Android, Apple iOS, etc.
Now-a-Days Operating System is present on almost all electronic gadgets like Mobiles, iPads,
Tablets, PC‟s, Smart TV‟s etc. Some of the Mobile Operating Systems are Google Android OS, Apple iOS,
BlackBerry and Windows etc.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 1 II.B.Sc III-Sem Operating System-Major
,***********(Q) Explain about History or Generations of Operating System?
English Mathematician Charles Babbage (1792-1871) developed Analytical Machine (AI) the first true
digital computer which was purely mechanical, and the technology of his day could not produce. Operating
Systems have evolved through a number of distinct generations which spans roughly too few decades.
I. First Generation (1945 – 1955):
First generation was also known as Vacuum Tube.
The Machines were so primitive that programs were often entered one bit at a time on rows of
mechanical switches (Plug Boards).
No programming languages were available (not even Assembly Languages).
The earliest electronic digital computers had no Operating System.
Technology Vacuum Tubes
Programming PlugBoard (Setting some switches)
Programming Language Machine Language / Binary 1 or 0
Tasks Tables of Sine, Cosine, Logarithms
Operating System None (Instead Mechanical Gear Systems were used)
II. Second Generation (1955 – 1965):
Second Generation computers were also known as Transistors and Batch Systems.
By the late 1950‟s, Punched Cards were introduced.
The General Motors Research Laboratories implemented the first Operating System in early 1950‟s
for their Mainframe IBM S/360.
The systems of the 1950‟s generally ran one job at a time.
These were called Single-Stream Batch Processing Systems, because programs and data were
submitted in Groups or Batches.
A Batch referred to a set of similar tasks or jobs. Job Control Language was used to create the
instructions to execute the job.
The instructions were punched on a card which was then loaded onto a tape that had several such
cards and then it was finally sent to the processor.
Programs were known as job. Jobs were entered in groups called as Batch.
Second-generation computers were used for scientific and engineering calculations of physics and
engineering.
Technology Transistors
Programming Punch cards and Magnetic Taps
Programming Language Assembly Level Languages & FORTRAN.
Tasks Scientific and Engineering
Computer Mainframes
Operating System Batch System
III. Third Generation (1965 – 1980):
Third Generation computers were known Integrated Circuit (IC‟s).
By the 1950‟s, punched cards were introduced. The General Motors Research Laboratories the
systems of the 1960‟s were also Batch Processing Systems, but by running several jobs at once by
introducing three new concepts namely Multiprogramming, Spooling and Timesharing.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 2 II.B.Sc III-Sem Operating System-Major
, Multiprogramming: Multiprogramming is a technique in which several jobs are in main memory at
once; a processor is switched from job to job as needed to keep several jobs running simultaneously
by keeping the peripheral devices in use.
Spooling: Spooling stands for “Simultaneous Peripheral Operations On-Line”. Spooling that has an
ability to read jobs from cards onto the disk. Spooling technique is like Thread being spun to a spool
so that it may be later be unwound as needed.
Example: To print something, the program outputs the data on to a disk, once the data is
stored on the disk; CPU starts another program without waiting for the printer. When the
printer is ready the output stored on the disk will be printed by using the printer without the
help of CPU.
Timesharing: Timesharing systems were developed to Multiprogramming large number of
simultaneous interactive users. Timesharing is a technique used in Multiprogramming, in which each
user has an on-line (i.e, directly connected) terminal. Because the user is present and interacting
with the computer, the computer system must respond quickly to user requests, otherwise user
productivity could suffer.
Third generation computers were used for large scientific calculations and massive commercial data-
processing runs.
Technology Integrated Circuits (IC)
Type of Operating System Multi-Programming IBM OS S/360 & Timesharing & Spooling
Programming Language High-Level Languages like C, C++, Java, Visual Basic, and JavaScript
Hardware Complier and Interpreted
IV. Fourth Generation (Since 1980):
Fourth generation computers were also known as Personal computers.
With the development of Large Scale Integration Circuits (LSIC).
Microprocessor technology evolved to the point that it becomes possible to build desktop computers
as powerful as the Mainframes of the 1970‟s.
Two Operating Systems have dominated the personal computer scene: MS-DOS for Inter based PC‟s
and UNIX (SUN Microsystems) for the large personal computers using the Motorola 6899 CPU family.
Later Microsoft introduces Graphical User Interface (GUI) Operating System called „Windows‟.
Various versions of windows are Windows 95, Windows 98 (ME), Windows NT renamed as Windows
2000.
Later Network Operating System and Distributed Operating Systems were introduced.
Network Operating Systems uses Network Interface cards to provide user to work with many
computers. Example of Network Operating Systems MS Windows 2000, Xp, SUN Solaris, LINUX etc.
Distributed Operating Systems are used to run the applications at various processors of same
machine. Example of Distributed Operating Systems included UNIX®, LINUX® and Windows®.
Technology Large Scale Integrated Circuits (LSIC)
Type of Operating System DOS, Windows, MacOS, UNIX, LINX
Programming Language High-Level Languages like Database programming and Scripting.
Hardware Circuits / Chips & Transistors
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 3 II.B.Sc III-Sem Operating System-Major
, V. Fifth Generation (Since 1990):
Fifth generation was also known as Mobile Computer, made by using Ultra / Very Large Scale
Integrated Chips. New Operating Systems like Blackberry OS, iOS, Android became popular in the
market.
Devices become more portable and smaller in size. Artificial intelligence is used on a large scale to
construct a device, which uses natural language processing for analysis of input. Computers in this
era were capable of self-learning
Technology Very Large Scale Integrated Circuits (VLSIC)
Type of Operating System Android, iOS, Blackberry OS
Programming Language High-Level Languages like Artificial Intelligence Programming
Hardware Handheld devices, PDA, Smart Phone
(Q) Explain various Evolution of Operating System?
Evolution of Operating System: Operating Systems have evolved in past years. It went through several
changes before getting its original form. These changes in the Operating System are known as the Evolution
of Operating Systems.
1. Serial Processing
2. Batch Processing / Batch Systems.
3. Multiprogramming
4. Multitasking or Time-Sharing System
1. Serial Processing:
Users access the computer in series. From the late 1940's to mid-1950's, the programmer interacted
directly with computer hardware i.e., no Operating System.
These machines were run with a console consisting of display lights, toggle switches, some form of
input device and a printer.
Programs in machine code are loaded with the input device like card reader. If an error occurs the
program was halted and the error condition was indicated by lights.
Programmers examine the registers and main memory to determine error. If the program is success,
then output will appear on the printer.
Main problem here is the setup time: That is single program needs to load source program into
memory saving the compiled (object) program and then loading and linking together.
2. Simple Batch Systems:
To speed up processing jobs with similar needs are batched together and run as a group. Thus, the
programmers will leave their programs with the operator. The operator will sort programs into
batches with similar requirements.
The problems with Batch Systems are:
Lack of interaction between the user and Job. CPU is often ideal, because the speeds of the
mechanical I/O devices are slower than CPU.
For overcoming this problem use the Spooling Technique. Spool is a buffer that holds output for a
device, such as printer, that cannot accept interleaved data streams.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 4 II.B.Sc III-Sem Operating System-Major
Revised Syllabus Under CBCS W.E.F. 2023-2024
III-SEMESTER: Course 8: OPERATING SYSTEM (OS)
SRI VENKATESWARA UNIVERSITY, TIRUPATI.
UNIT – I
Introduction to Operating System
(Q) What is Operating System?
Introduction:
An Operating System acts as an intermediary between the user of a computer and computer
hardware. The purpose of an Operating System is to provide an environment in which a user can execute
programs conveniently and efficiently.
An Operating System is software that manages computer hardware. The hardware must provide
appropriate mechanisms to ensure the correct operation of the computer system and to prevent user
programs from interfering with the proper operation of the system.
Definition of Operating System:
An Operating System is define as a set of programs that are used to control various resources of a
computer system to provide efficient sharing of resources among various application programs that are
executed by various users.
(OR)
An Operating System is a program that controls the execution of application programs and acts as an
interface between the user and the computer hardware. From system point of view, the Operating System
acts as:
Resource Allocator: To allocate various resources to the programs.
Manager: To manage all the resources.
Controller: To control the all the activities of I/O devices and user programs.
Control Program: To manage the execution of user programs.
Examples of Operating System are MS-Windows (Windows Xp, Windows 2003 Server, Windows Vista,
Windows 7, Windows 8, Windows 10, and Windows 11), Linux, Android, Apple iOS, etc.
Now-a-Days Operating System is present on almost all electronic gadgets like Mobiles, iPads,
Tablets, PC‟s, Smart TV‟s etc. Some of the Mobile Operating Systems are Google Android OS, Apple iOS,
BlackBerry and Windows etc.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 1 II.B.Sc III-Sem Operating System-Major
,***********(Q) Explain about History or Generations of Operating System?
English Mathematician Charles Babbage (1792-1871) developed Analytical Machine (AI) the first true
digital computer which was purely mechanical, and the technology of his day could not produce. Operating
Systems have evolved through a number of distinct generations which spans roughly too few decades.
I. First Generation (1945 – 1955):
First generation was also known as Vacuum Tube.
The Machines were so primitive that programs were often entered one bit at a time on rows of
mechanical switches (Plug Boards).
No programming languages were available (not even Assembly Languages).
The earliest electronic digital computers had no Operating System.
Technology Vacuum Tubes
Programming PlugBoard (Setting some switches)
Programming Language Machine Language / Binary 1 or 0
Tasks Tables of Sine, Cosine, Logarithms
Operating System None (Instead Mechanical Gear Systems were used)
II. Second Generation (1955 – 1965):
Second Generation computers were also known as Transistors and Batch Systems.
By the late 1950‟s, Punched Cards were introduced.
The General Motors Research Laboratories implemented the first Operating System in early 1950‟s
for their Mainframe IBM S/360.
The systems of the 1950‟s generally ran one job at a time.
These were called Single-Stream Batch Processing Systems, because programs and data were
submitted in Groups or Batches.
A Batch referred to a set of similar tasks or jobs. Job Control Language was used to create the
instructions to execute the job.
The instructions were punched on a card which was then loaded onto a tape that had several such
cards and then it was finally sent to the processor.
Programs were known as job. Jobs were entered in groups called as Batch.
Second-generation computers were used for scientific and engineering calculations of physics and
engineering.
Technology Transistors
Programming Punch cards and Magnetic Taps
Programming Language Assembly Level Languages & FORTRAN.
Tasks Scientific and Engineering
Computer Mainframes
Operating System Batch System
III. Third Generation (1965 – 1980):
Third Generation computers were known Integrated Circuit (IC‟s).
By the 1950‟s, punched cards were introduced. The General Motors Research Laboratories the
systems of the 1960‟s were also Batch Processing Systems, but by running several jobs at once by
introducing three new concepts namely Multiprogramming, Spooling and Timesharing.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 2 II.B.Sc III-Sem Operating System-Major
, Multiprogramming: Multiprogramming is a technique in which several jobs are in main memory at
once; a processor is switched from job to job as needed to keep several jobs running simultaneously
by keeping the peripheral devices in use.
Spooling: Spooling stands for “Simultaneous Peripheral Operations On-Line”. Spooling that has an
ability to read jobs from cards onto the disk. Spooling technique is like Thread being spun to a spool
so that it may be later be unwound as needed.
Example: To print something, the program outputs the data on to a disk, once the data is
stored on the disk; CPU starts another program without waiting for the printer. When the
printer is ready the output stored on the disk will be printed by using the printer without the
help of CPU.
Timesharing: Timesharing systems were developed to Multiprogramming large number of
simultaneous interactive users. Timesharing is a technique used in Multiprogramming, in which each
user has an on-line (i.e, directly connected) terminal. Because the user is present and interacting
with the computer, the computer system must respond quickly to user requests, otherwise user
productivity could suffer.
Third generation computers were used for large scientific calculations and massive commercial data-
processing runs.
Technology Integrated Circuits (IC)
Type of Operating System Multi-Programming IBM OS S/360 & Timesharing & Spooling
Programming Language High-Level Languages like C, C++, Java, Visual Basic, and JavaScript
Hardware Complier and Interpreted
IV. Fourth Generation (Since 1980):
Fourth generation computers were also known as Personal computers.
With the development of Large Scale Integration Circuits (LSIC).
Microprocessor technology evolved to the point that it becomes possible to build desktop computers
as powerful as the Mainframes of the 1970‟s.
Two Operating Systems have dominated the personal computer scene: MS-DOS for Inter based PC‟s
and UNIX (SUN Microsystems) for the large personal computers using the Motorola 6899 CPU family.
Later Microsoft introduces Graphical User Interface (GUI) Operating System called „Windows‟.
Various versions of windows are Windows 95, Windows 98 (ME), Windows NT renamed as Windows
2000.
Later Network Operating System and Distributed Operating Systems were introduced.
Network Operating Systems uses Network Interface cards to provide user to work with many
computers. Example of Network Operating Systems MS Windows 2000, Xp, SUN Solaris, LINUX etc.
Distributed Operating Systems are used to run the applications at various processors of same
machine. Example of Distributed Operating Systems included UNIX®, LINUX® and Windows®.
Technology Large Scale Integrated Circuits (LSIC)
Type of Operating System DOS, Windows, MacOS, UNIX, LINX
Programming Language High-Level Languages like Database programming and Scripting.
Hardware Circuits / Chips & Transistors
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 3 II.B.Sc III-Sem Operating System-Major
, V. Fifth Generation (Since 1990):
Fifth generation was also known as Mobile Computer, made by using Ultra / Very Large Scale
Integrated Chips. New Operating Systems like Blackberry OS, iOS, Android became popular in the
market.
Devices become more portable and smaller in size. Artificial intelligence is used on a large scale to
construct a device, which uses natural language processing for analysis of input. Computers in this
era were capable of self-learning
Technology Very Large Scale Integrated Circuits (VLSIC)
Type of Operating System Android, iOS, Blackberry OS
Programming Language High-Level Languages like Artificial Intelligence Programming
Hardware Handheld devices, PDA, Smart Phone
(Q) Explain various Evolution of Operating System?
Evolution of Operating System: Operating Systems have evolved in past years. It went through several
changes before getting its original form. These changes in the Operating System are known as the Evolution
of Operating Systems.
1. Serial Processing
2. Batch Processing / Batch Systems.
3. Multiprogramming
4. Multitasking or Time-Sharing System
1. Serial Processing:
Users access the computer in series. From the late 1940's to mid-1950's, the programmer interacted
directly with computer hardware i.e., no Operating System.
These machines were run with a console consisting of display lights, toggle switches, some form of
input device and a printer.
Programs in machine code are loaded with the input device like card reader. If an error occurs the
program was halted and the error condition was indicated by lights.
Programmers examine the registers and main memory to determine error. If the program is success,
then output will appear on the printer.
Main problem here is the setup time: That is single program needs to load source program into
memory saving the compiled (object) program and then loading and linking together.
2. Simple Batch Systems:
To speed up processing jobs with similar needs are batched together and run as a group. Thus, the
programmers will leave their programs with the operator. The operator will sort programs into
batches with similar requirements.
The problems with Batch Systems are:
Lack of interaction between the user and Job. CPU is often ideal, because the speeds of the
mechanical I/O devices are slower than CPU.
For overcoming this problem use the Spooling Technique. Spool is a buffer that holds output for a
device, such as printer, that cannot accept interleaved data streams.
Shaik Mohammad Fareed. MCA, M.Sc, IRPM. Page 4 II.B.Sc III-Sem Operating System-Major
