1. Computer Software

2. Introduction
A set of instructions given to the computer to solve a particular problem is called software
Also called computer program
Software tells the computer what to do and how to do
Hardware operates under the control of given set of instructions
Software is developed in computer programming language

3. Types of Software
System Software
Application Software

4. Application Software
A program or set of programs that are specially designed to solve the specific problem of users
Different kinds of application software
Commercial software, scientific software, financial packages, games, multimedia etc
Two main categories
Custom built software
Packaged Software

5. Custom-Built Software
Developed for a particular organization or customer
Also known as customize software
For example, software developed to maintain the records of students of a particular college

6. Packaged Software
Developed by software development organization for sale to the general public
Used to solve some common problems of many people or users
Examples
Word Processing Software
Spreadsheet Software
Database Management Software
Communication Software
Presentation Software
Graphics Software

7. Examples of Graphics Software
Computer Aided Design
Desktop Publishing
Painting Software
Image Editing Software
Video & Audio editing Software
Multimedia Authoring Software
Web Page Authoring Software

8. System Software
A program or set of programs that is specially designed to control different operations of the computer system
Controls the working of different parts of the computer
Enables the other application programs to execute properly
Examples:
Operating Systems
Utility Programs
Device Drivers
Language Processors

9. Operating System
An operating system is a collection of system programs that controls and coordinates the overall operation of the computer system
Also provide the interface between the user and the computer system
A computer needs an operating system to do work

10. Tasks of Operating System
Accepts input from input devices
Sends output to the output devices
Manages the application program in memory
Manages the files on the storage devices
Manages & controls the I/O devices

11. Operating System

12. Parts of Operating System
Resident Part
Also known as kernel
Contains the critical functions
Loaded into the main memory during the booting process of computer
Non-Resident Part
Loaded into the main memory when required

13. Examples of Operating System
Disk Operating System developed by Microsoft
Operating System 2 developed by IBM
XENIX developed by Microsoft
Windows developed by Microsoft

14. Operating System Functions
When computer is turned on the operating system is loaded into the main memory from the disk
Most of the operating system perform the similar functions

15. Operating System Functions
Booting a Computer
User-Interface
Running Programs
Managing Files
Memory Management
Scheduling Jobs
Configuring Devices
Establishing Internet Connection
Controlling Network
Task Management

16. Booting a Computer
The operating system consists of supervisor portion and a set of system programs
When the computer is switched on, the supervisor portion of the operating system is loaded in the RAM from the disk
The process to start or restart a computer is called booting process
Two Types
Cold boot
Warm Boot

17. Steps of Booting Process
When you turn on the computer, the electric signals make active the processor chip. The processor loads the instructions in ROM. These are computer start up instructions called Firmware. It is BIOS that is automatically activated when the computer is turned on and tests the computer hardware. This type of testing is called Power-On Self Training (POST)
After the POST process, the BIOS searches the operating system files called system files on the disk and load these into RAM and then the operating system takes the control of the computer

18. User Interface
User interface means how the user interacts with the computer to perform various tasks
User runs the application programs, open the documents, enters the data, print the output report
The operating system plays the main role for interfacing between user and computer
The hardware devices like keyboard, mouse, monitor are used for interfacing
Two main types of user interface
Command Line User Interface
Graphical User Interface

19. Running Programs
The operating system also provides the interface between the programs and the user
Through program, the user access other computer resources
There is built in instruction in program known as “system calls” that are used to request the services from the operating system
The application program sends the request to the operating system and the operating system gives the result back to the operating system

20. Running Programs Saving the data from memory in files on the disk
Loading the files from disk into memory
Sending the document on the printer
To copy or move the data from one document to another
For the services of hardware
To prepare the disk to store data etc

21. Managing Files
The data and programs are stored permanently on the disk for future use
The files are stored on the disk by giving a file name
The files are placed or stored in folders or directories
A folder may contain file or sub folders
The operating system maintain a list of these files and folders in the staring area of the disk called FAT
File Viewer utility program is used the names of files and sub folders
For Example, Windows Explorer

22. Memory Management
Memory unit has very important role for data processing
Processor takes data and instructions from RAM during processing
The operating system loads the data and programs into RAM and allocates the memory areas and manage these properly
When the program is closed, the operating system clears the memory area allocated to that program and its data

23. Memory Management
During data processing some operating system use the hard disk as memory, called virtual memory
During processing, operating system transfer some of data from RAM to hard disk and reload when required, called swapping
This technique of swapping data between memory and hard disk is called paging
Operating systems spends a lot of time in paging process, instead of executing the application software, it is referred to as Thrashing

24. Scheduling Jobs
A job is an activity or operation that a processor performs
May be receiving data from input device
Sending output to the output device
Loading data from disk into RAM
Operating system determines the order in which jobs are to be processed
First Come First Serve Basis
Priority Basis
If there are multiple jobs of the same nature, the operating system place the request in buffer, temporary, process called spooling

25. Configuring Devices
The functions of devices attached with the computer are controlled by the special system software called device drivers
Device driver tells the operating system how to communicate with a device
Each device has its own device driver
When you boot a computer, the operating system loads each device driver
Usually the operating system has built-in device driver for commonly used input/output devices
Operating system automatically install these driver

26. Establishing Internet Connection
Operating System provides means to establish connection between your computer and the ISP (Internet Service Provider) server
Some Operating System have built-in program used to access the information on the internet
Information downloaded from the internet is managed by the operating system in RAM as well as in disk

27. Controlling Network
Some operating system are specially developed for networking
Called Network Operating System (NOS)
A network operating system organizes and coordinates multiple users and make it possible to access and share resources on network
Overall functions of users are controlled by NOS
Creation of account of new user
Deletion of user account if required
NOS also has security features
Require a user name and password to access the network
Cannot be accessed by un-authorized persons

28. Task Management
A task is an operating such as storing, printing, calculating etc
A computer can perform many tasks at a time
Some operating system can handle more than one program at the same time
The operating system manage all these tasks
Some operating system have single user functionality and can support only one user at a time

29. Task Management The operating system performs the following tasks:
Multi Tasking
Multi Programming
Multiprocessing
Time Sharing
Multithreading
Virtual Memory
Spooling

30. Types of Operating System
In the past, operating system were computer dependent
An operating system running on one machine could not be run another different type of machine
Three basic categories of operating system are:
Personal Computer Operating System
Network Operating System
Embedded Operating System

31. Personal Computer Operating System
Also called stand alone operating system or single user operating system
Used to operate personal computers
Examples
DOS
Mac OS
Windows

32. Network Operating System
Supports the network
Typically resides on a server and controls the devices or computers connected to the network
Examples:
Windows NT Server
Windows 2000 Server
UNIX
Solaris
Novell’ s Netware

33. Embedded Operating System
Different special electronic devices and handheld computers are also controlled by the operating systems that are stored in the ROM chip
Examples:
Windows CE
Pocket PC 2002
Palm Operating System

34. Difference between Windows & DOS
DOS provides command line Interface, while Windows provides Graphical User Interface
DOS is single tasking operating system, While Windows is multi-tasking operating system
DOS does not provide plug and play feature, while Windows provide plug and play feature

35. Utility Programs
A software that helps the user to solve the specific problems related to the software and hardware is called utility programs
It is system software
A large number of utility programs are available for the service of hardware and software
Most operating system include various utility programs
While others are available on CDs or can be downloaded from the internet

36. Utility Programs File Viewer File Compression
Diagnostic Utility Program
Un-Installer
Disk Scanner
Disk Defragmenter
Back up Utility

37. Device Drivers
The programs that operate and control the devices attached to the computer are called device drivers
The keyboard, mouse, disk driver, CD-ROM drive, Modem, Printer etc require to install software that tells the computer how to use the device
When you purchase a new hardware device, manufacturer of the device also provides you a disk containing a device driver

38. References
Introduction to Information Technology by Riaz Shahid, CM Aslam and Safia Iftikhar
The Concepts of Information Technology by Imran Saeed, Ahsan Raza, Tariq Mehmood and Zafar Hussain