The document defines and describes operating systems. It states that an operating system is an interface between the user and computer that enables programs to run. It performs basic tasks like controlling memory, input/output devices, file management, and prioritizing requests. An operating system has four main layers - hardware, operating system software, system programs, and application programs. It also classifies operating systems as single-user or multi-user and describes their main differences. Key functions of operating systems include program creation/execution, input/output operations, error detection, resource allocation, accounting, and protection.

1. OPERATING
SYSTEM

2. What is operating
system?
 Operating System is an interface between the
user and computer.
 OS is a software, which makes a computer to
actually work.
 It is the software which enables to all the
programs that we use.
 OS acts as an interface between the
application programs and machine hardware.

3. What OS does?
An Operating System performs basic tasks such as
Controlling and allocating memory
Controlling input and output devices
Managing file system
Facilitating networking and
Prioritizing system requests.

4. Application
System programs
Software(OPERATINGSYSTEM)
Hardware
Structure of operating system?
Continued…………….

5. (1)HARDWARE:-Hardware consists of CPU, MAIN MEMORY,
INPUT/OUTPUT devices, etc.
(2) SOFTWARE(OPERATING SYSTEM):-Software includes
process management routines,
memory management routines, input/output control routines, file
management routines.
(3)SYSTEM PROGRAMS:-This layer consists of compilers, assemblers,
linker etc.
(4)APPLICATION PROGRAMS :-This is dependent on users need.
Ex.-Railway reservation system,
Bank database management system, etc.

6. FUNCTIONS OF OPERATING SYSTEM?
 The main functions of “OPERATINNG SYSTEMS” are:-
 Program creation
 Program execution
 Input /Output operations
 Error detection
 Resource allocation
 Accounting
 protection

7. CLASSIFICATION OF OPERATING SYSTEM?
 Operating System can also be classified as:-
SINGLE USER SYSTEMS
MULTI-USER SYSTEMS

8. Single user operating system:-
Provides a platform for only one
user at a time.
They are popularly associated with
desktop OPERATING SYSTEM which
run on stand alone system where no
user accounts are required.
Ex-DOS

9.  Provides regulated access for a number of
users by maintaining a database of known
users.
 Refers to computer systems that support
two or more users.
 Another term for multi user is time
sharing.
 All mainframes and all multi users system.
 Ex:-Unix, Multics, etc.
Multi user operating system:-

10. MULTIPROGRAMMING
:-It is technique to execute number of programs simultaneously
by a single processor
In multiprogramming, number of processes reside in main
memory at a time.
The OS picks and begins to executes one of the jobs in the
main memory.
If any I/O wait happened in a process, then CPU switches from
that job to another job
Hence CPU is not idle at a time.

11.  Time Sharing Systems
Time sharing or multi tasking system is a
logical extension of multiprogramming.
Multiple jobs are executed by switching
the CPU between them.
In this, the CPU time is shared by
different processes, so it is called as
“TIME SHARING SYSTEMS.”
Time slice is defined by the OS, for
sharing CPU time between processes.
Ex:-Multics, Unix, etc.
The End

12. -:Presented By:-
SUMIT KUMAR GUPTA
2015-2017
Department of Library &
Information Science
Lucknow university