This is Operating System Subject Notes where you can explore whole study related to Operating System.
This file consist of 5 units: Basics of Operating System, Process management, Process Synchronization & Deadlock, Memory management, and Storage Management respectively.
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Basic Overviews:
What is an Operating System?
Operating SYstem is a fundamental Software of the computer which Establishes the
communication between User & Computer System or Hardware.
Or
Operating System is a program which acts as an Intermediary b/w the user and Computer
hardware.
The one program which run all the time in the computer is called kernel, is the part of
operating system.
Goals of operating System:
● Establish the communication b/w user and computer hardware.
● Execute the user program and make any user problem easier.
● Use the Computer Hardware in an Efficient manner.
● Make the use of computer system convenient.
Structure of Computer System
Computer System can be divided into 4 components:
1. Hardware: These are the physical component of the Computer used to perform
specific tasks like printer, Speaker, Monitor, Mouse, and more.
2. Operating System: It is the special program which is used to operator the computer
system. It establish the communication b/w user & computer hardwares.
3. Application Program: Application Programs are special kind of programs used to
perform a single specific operation like Word processor, Any Game, Compiler, Video
game, and more.
4. Users: Every system require any user for giving Instruction so it is also a part of
Structure Computer System.
,What Operating System Do?
There are lot of works operating system do, but some basic & fundamental Works of
Operating system are:
Resource Allocation: The major task of the operating system is allocating resources to
multiple processes with scheduling. Resource allocation is another big concept of operating
system where multiple resources are allocated and deallocated by multiple processes at the
same time.
Task Management: Task management is also a duty of operating system in Computer
where OS decide the priority & timing of each of task.
Multi User handling: Some operating systems are also multi user supported which means a
single operating system can handle the task of multiple users at the time with efficiency &
correctness.
Memory management: The allocation of memory to various live programs, is also perform
by the operating system.
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Syllabus Topics:
Generations of Operating System:
There are total four generations of OS:
,1. The First Generation ( 1945 - 1955 ): Vacuum Tubes and
Plugboards
● Digital computers were not constructed until the second world war.
Calculating engines with mechanical relays were built at that time. However,
the mechanical relays were very slow and were later replaced with vacuum
tubes.
● These early computers were designed, built and maintained by a single group
of people.
● Programming languages were unknown and there were no operating systems
so all the programming was done in machine language. All the problems were
simple numerical calculations.
● By the 1950’s punch cards were introduced and this improved the computer
system.
● Instead of using plugboards, programs were written on cards and read into
the system.
, 2. The Second Generation ( 1955 - 1965 ): Transistors and Batch
Systems:
● Development of the actual operating system concept was introduced after the
invention of the transistor, allowing computers to be sold to demanding
customers.
● These machines were known as mainframes and were locked in
air-conditioned computer rooms with staff to operate them.
● The Batch System was introduced to reduce the wasted time in the computer.
A tray full of jobs was collected in the input room and read into the magnetic
tape.
● Then the batch operating system was loaded in which read the first job from
the tape and ran it. The output was written on the second tape.
● After the whole batch was done, the input and output tapes were removed
and the output tape was printed.
3. The Third Generation ( 1965 - 1980 ): Integrated Circuits and
Multiprogramming
● Until the 1960’s, there were two types of computer systems like the scientific and the
commercial computers.
● The third generation operating systems introduced multiprogramming which is th3
biggest achievement of OS at that time.
● This meant that the processor was not idle while a job was completing its I/O
operation. Another job was scheduled on the processor so that its time would not get
wasted.
4. The Fourth Generation ( 1980 - Present ): Personal Computers
● Personal Computers were easy to create with the development of large-scale
integrated circuits.
● These were chips containing thousands of transistors on a square centimetre of
silicon. Because of these, microcomputers were much cheaper than minicomputers
and this made it possible for a person to own one of them.
Types of OS:
Batch Operating System:
● Also called Multiprogramming Operating Systems.
● The users of the batch operating system do not interact with the computer directly.
Each user prepares his job on an offline device like punch cards and submit it to the
computer operator.
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