The document discusses the key features and functions of operating systems. It describes how operating systems allocate resources, manage devices and memory, and allow multiple programs to run simultaneously. Examples are given of some popular operating systems for microcomputers, minicomputers and mainframes. The functions of an operating system include input/output management, memory management, file management, and human-computer interfacing. Popular modern operating systems like Windows, Mac OS, Linux, and UNIX are also overviewed.

2. INTRODUCTION
Features of an Operating System
Operating System abbreviated as OS.
 It is responsible for
 Allocating system resources
 Processor times
 Disk space
 Managing peripheral devices
It manages CPU, Input, Output, Network equipments.
Microcomputer has a much simple OS than the
Mainframe

3. INTRODUCTION
Examples of Microcomputer OS:-
 Windows
 DOS
 OS/2
Examples of Minicomputer OS:-
 UNIX
 OS/400 etc.
Examples of Mainframe computer OS:-
 MVS (Multiple Virtual Storage)
 VAX (Virtual Address eXtension) etc.

4. Functions of An Operating System
1. Input / Output Device Management:-
Accept data through input devices transfer to memory and
sending to correct output devices.
1. Data Management:-
Manage data in the form of Directory and files in disk.
1. Memory Management:-
Allocate memory for each program even the OS also in its
memory for concurrent running purpose.
1. Backing Store Management:-
OS sending data from disk to memory and vice versa. It
stores the data in disk allocating space for the
directory and file.

5. Functions of An Operating System
5. Job Management:-
Set priority to the jobs and allocates memory to execute
them.
5. Resource Management and Scheduling:-
It manages its all resources. It also runs several programs at
once (known as programming). It does not do task as
per given order. But it manages the sequence to run
program and manages the memory space also.
5. Network Management:-
A user can enter into any network using user id and
password for security purpose. OS allows to access the
particular data or program to the authorized user in the
server.

6. Functions of An Operating System
8. File Management:-
The management of the file system is done by
the file manager of Operating System. To
save a file under a file name. The file
manager holds the information of the files:
• File type (folder file, sys file, hidden file, batch file, exe file
or text file.
• Location of storage
• File size in bytes.
• Access rights (who and how can the file accessed i.e. read
only, read-write, write only and delete permission.
• Date information (date of creation, date of modifiation, last
modify date etc.) purge

7. Functions of An Operating System
9. Interrupt Handling:-
 An interrupt is a signal to a processor.
 An event occurring on peripheral devices.
 A voluntary event occurring within process.
 An involuntary event occurring within a process.
 An event occurred by the action of operators.
 A timer interrupt.
9. Batch Processing:-
 It groups similar kind of jobs together and forms batch
files. These files are later executed when a request is
encountered.
9. Program Execution:-
 It loads the application programs in the memory and
executes them.

8. Functions of An Operating System
12. Virtual Storage:-
 It increases the capacity of the main memory without
increasing the size. First it broken the task into pages and
send them to execute in sequence page wise from
secondary storage device.
12. Error Handling:-
 It transforms the user about any error that occurs while
the execution of a program.
12. Security:-
 It deals with system security by monitoring the
accessibility options provided to program and data.

9. Functions of An Operating System
15. On-line Processing:-
 It processes the data instantaneously in on-line
processing. When a request is encountered, the software
instantly answers it and sends back to the exact node
where the request generated.
15. Human Computer Interface (HCI):-
 It allows the computer to communicate with the user.
1. Command driven:-
 This interface requires users to enter commands using the
special words known as “keywords”.
1. Menu Driven:-
 On-screen, text based menus that show all the options
available.
1. Graphical User Interface:-
 Most popular interface. It displays all the programs, files and
connections through small illustrations called “icons”.

10. Functions of An Operating System
17. Multiprogramming:-
 It can manipulate more than one program in the memory
at the same time.
1. Multi-user:-
 It allows more than one user to work at the same
time. MVS, VAX are the examples of the multi
user OS.
1. Multiprocessing:-
 It allows the utilization of multiple CPU in a single
computer system (parallel processing).
1. Multitasking:-
 It allows the execution of more than one program
on the same CPU simultaneously.

11. Popular Operating Systems
UNIX:-
UNIX was developed at AT&T Bell Labs
in early 1970s.
Features:-
Multitasking, Creation, synchronization and
termination of processes.
File Management system provides i. Directory
control, ii. File naming, iii. Ability of control
access files, shared access.

12. Popular Operating Systems
MS-DOS (Microsoft Disk Operating
System) :-
Originally developed for IBM Pc in 1981.
Now it is being used by Intel based PCs.
DOS commands are used for managing
files and directories.
It has limitation functionalities like
management of peripheral devices and no
multitasking.

13. Popular Operating Systems
MAC (Macintosh) :-
Apple Incorporation released the original
Macintosh operating system in 1984.
It is a GUI based OS.
It is easiest for beginning computer users.

14. Popular Operating Systems
Windows 95, 98 and 2000 :-
GUI, developed by Microsoft for Intel
microprocessors.
It support multiprocessing, multitasking.
It allows transfer of information between
applications.
It offers: better stability, improved
internet connectivity, updated drivers for
new peripherals including DVD-ROM
disks etc.

15. Popular Operating Systems
Windows CE :-
GUI, mainly designed for the palmtops.
It runs the applications like Office
applications.
It enables the user to work on them and
transfer to Desktops for printing purpose.
It includes scheduling calendar, address
book, e-mail, web browsing etc.
It also includes handwriting recognition
and voice recording.

16. Popular Operating Systems
Windows NT (New Technology):-
Specially designed for Client/Server
systems.
It is divided into two components Windows
NT workstation and Windows NT Server.
It is meant for Desktop computer.
Windows NT Server supports high security
level, directory services and web server.

17. Popular Operating Systems
Windows XP :-
It is introduced in 2001 from Microsoft’s Windows
family of operating system.
Its previous version was Windows Me.
It gives the user a more stable and reliable environment
then previous versions of Windows.
There are two versions of Windows XP, Home and
Professional.
It includes plug and play features for connecting to
wireless networks.

18. Popular Operating Systems
LINUX :-
The student of Finnish University named Linux
Torvalds created Linux in 1991.
It is a fastest growing OS for Intel based personal
computers.
It includes all the features of UNIX (multitasking,
virtual memory, Internet support, multiprocessing and
GUI).
LINUX is distributed using the Open Software
Foundation’s General Public License (GPL).
Linux could be obtained and used for free.