This document discusses operating systems and their functions. It defines an operating system as a program that mediates between application programs and hardware components, acting as an interface between users and computer resources. The key needs for an operating system are to make proper use of hardware resources, provide a consistent way for applications to deal with hardware without knowing details, and control and coordinate all computer system activities like memory allocation, process prioritization, networking and file management. The major functions of an operating system are device management, process management, memory management and storage management. It also discusses process scheduling and the types of scheduling that can occur.

1. OPERATING SYSTEM
BY
PRIYANKA SHARMA
ASSISTANT PROFESSOR
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2. INTRODUCTION
An operating system is the core component of computer.
It is a program that mediates between application programs and
hardware components.
An interface between the user and computer hardware resources.
A collection of software or series of programs which performs
various types of functions for the purpose of managing and
organizing files.
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3. NEEDS FOR OPERATING SYSTEM
A computer would be useless without operating system as it is not
able to do anything on its own.
 As the application programs are not able to access the hardware
resources directly. Therefore, an operating system is needed to make
the proper usage of hardware resources.
It provides a stable and consistent way for most of the application to
deal with the hardware without having to know all the details of the
hardware.
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4. NEEDS FOR OPERATING SYSTEM
It makes the computer ready for taking instructions from the user.
The operating system controls and co-ordinates all the activities of a
computer system.
The operating system performs the basic tasks such as controlling
and allocating memory, prioritising the processes for instructions,
networking, facilitating and managing files.
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5. OPERATING
SYSTEM
It acts as the interface
between the users and
hardware of the
computer.
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6. FUNCTIONS OF OPERATING
SYSTEM
oDevice management:-
In a computer system there is a lot of speed mismatch between the
CPU and the input output devices.
The job of an operating system is to maintain the balance between the
input output devices and it has to keep the CPU busy.
It includes the management of speed of different devices , unit of
transfer, sharing of resources etc.
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7. FUNCTIONS OF OPERATING
SYSTEM
oProcess management
The operating system must guarantee that the each process or a
running application is treated equally in terms of the time allocated
for CPU to them.
It means that the processor should be efficiently utilised.
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8. FUNCTIONS OF OPERATING
SYSTEM
oMemory management
It is the act of managing the computer memory as each process should
have sufficient memory for its execution.
The different types of memory in the system should be utilized
properly so that the processes in the system can run effectively.
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9. FUNCTIONS OF OPERATING
SYSTEM
oStorage management:
It is the process which describes the technologies and processes used
by the system to improve t5he performance of data resources.
It is a wide process as it includes the virtualization, replication,
security, compression of data, analyses of traffic etc.
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10. PROCESSOR SCHEDULING IN
OPERATING SYSTEM
•As processes enter the system, they are put into a job queue.
•The processes which are actually in ready state in the main memory
are put into the ready queue.
•And the process waiting for the particular input output devices are
put in the device queue.
•The operating system has to select the processes from these queues.
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11. SCHEDULING OCCURS
Process switches from running state to waiting state.
Process switching from running state to ready state.
Process switching from waiting state to ready state.
Process terminates or exits.
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12. PRE EMPTIVE SCHEDULING
In this scheduling the CPU is allocated to a process and it keeps the
same until that process reaches to any waiting state.
It enters to the waiting state if it requires any input output device.
So the process releases the CPU only if it enters the waiting state.
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13. NON-PRE EMPTIVE SCHEDULING
In this scheduling the CPU is allocated to a process and it is never
released.
It means that once we have allocated the CPU to process it will not
switch until it is completed.
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14. www.advanced.edu.in

15. PRIYANKA SHARMA
ASSISTANT PROFESSOR
priyankavirgo.dixit@gmail.com
AITM
70 KM, DELHI-MATHURA ROAD, AURANGABAD,PALWAL
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