An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. The operating system is a component of the system software in a computer system. Application programs usually require an operating system to function.

2. Definition: Operating system is the system
software which is designed and developed for
performing the following functions:
• Main memory management or Disk
management
• C.P.U. Scheduling i.e. process management.
• Secondary memory management or disk
management.
• I/O control.
• Creation of users interfaces area, so the
users can specify their requirements in the
form of commands.

3. Software : The software which is System designed
and developed only for computer system for making it
more users friendly is called system software.
Eg.:- Dos, Unix, Linux, Windows Compilers, Loaders,
Linkers, Dbms etc.
Application Software: The software which is
designed and develops for solving the problems of
different application field as like business, commerce,
education, research & development, medical,
engineering & technology is called application software.
Eg:- (i) Hospital management system.
•Examination control system.
•Inventory control system
•Railway information system
•Payroll information

4. Types Of Operating System: On the basis
of number of users and number of C.P.Us.
There are three types of O.S.
•Single user O.S.
•Multi user O.S.
•Multi processors O.S.
•Single User Operating System:  The O.S.
in which one single C.P.U is used by single
user at a time is called single user O.S.

5. Multi User Operating System:  The O.S in which
single C.P.U is used by more than one users at one
time is called multi user O.S.
Multi Processor Operating System: The O.S
in which more than one C.P.U is used by a single
user or more than one user in the parallel way is
called multi processor O.S. It is also known as
parallel system. Because more than one C.P.Us
works parallel i.e. at the same time to complete
the big job in very less time.

6. Types Of Operating System : On the basis of configuration & features
there are seven type of O.S. :--
•Batch Operating system. (Single user O.S )
•Multi programmed batch operating system. (Single user O.S )
•Multi programmed operating system. (Single user O.S.)
•Time sharing operating system. (Multi user O.S )
•Multi tasking operating system. (Single user O.S )
•Batch Operating System : IT is the oldest O.S in which the jobs are
executed in batches and the batch monitor controls all the environment.
One batch contains more than one jobs After making the batches, the first
batch is loaded into the memory(magnetic tape or punch card) and control
is transferred to batch monitor by the user and control is transferred to
batch monitor. Batch monitor is the central soft ware component of the
batch O.S which control all the activities of batch operating system. It allots
the job one by one to C.P.U sequentially for execution and when jobs of
one batch are completed then after the control is transferred to user so that
the next batch can be loaded in the memory.

7. •Multi Programmed Batch Operating System
: When very small size of semi conductor
memory has been introduced in the form of
buffer between memory and I/O unit hen it
become possible to perform the CPU operation
and I/O operation at the same time and so the
CPU idle time has been reduced. This new
form of batch operating system is known as
multi programmed batch operating system

8. Multi Programming Operating System : When the
complete memory has been substituted by semi conductor
memory i.e. RAM then the batch concept of operating
systems has been totally removed and facility has been
given to user for lading , executing, suspending or
resuming the processes according to the choice of users
but CPU can execute only one lob at one time. This new
concept of the O.S. is known as multi programming
operating systemAdvantages:
•Urgent job can be completed at the same time when it is
required.
•The C.P.U ideal time is very less.
•The errors will be removed at the same time when at the
same the same time when they are generated.
•Average waiting time and response time is very less.

9. Multi Tasking Operating System :
Multi programming O.S + Time sharing O.S (But the slot time
is not fixed) . It is just similar to the multiprogramming
operating system. It is a good form of multiprogramming
operating system in which more then one jobs can share the
CPU time depending upon their priorities at the same time.
So, we can say that more than one jobs can be executed at
time By combining the approaches of multi programming O.S
and time sharing O.S, The new concept of O.S has introduced
in which we can load more than one jobs in the memory as
well as we can also run more than one jobs at the same time.
The C.P.U time is shared by the jobs on the basis of priorities
i.e. C.P.U slot time is not fixed for all the jobs i.e. it can vary on
the basis of requirements So we can say it is the improved
from of multi programming operating system.

10. COMPONENTS OF OPERATING SYSTEM
•Process Management
•Main memory Management
•Secondary Memory Management
•File Management
•I/O Control System
•Command Interpreter
•Protection
•Networking

11. For Full OS Notes Contact @ 7631205203,
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