It includes contents about computer software and its types, functions and types of operating system etc.

1. Introduction to Computer
Software
Mr. Roshan Bhattarai
Kathmandu, Nepal

2. Computer Software
• Computer hardware alone cannot perform any particular
function without software
• Software makes the hardware to function
• It acts as an interface between the user and the
computer
• Software is a set of instructions that runs the computer
system and performs the task of the user

3. Types of Software
• The two primary software categories are system
software and application software:
• System Software
– Operating System
– Utility Software
• Application Software
– General Purpose (Packaged)
– Specific Purpose (Tailored)

4. a) System software
• Is software that controls a computer
• runs applications on it,
• providing the resources and environment for application
software
• Includes operating systems (OS) and utility programs that
operate and maintain a computer system

5. i) Operating systems
• Operating systems are the most important programs that
run on a computer.
• manages and coordinates the functions performed by
the computer hardware
• serves as an intermediary between the user, application
programs and computer’s system hardware

6. • also known as master control program or a resource
manager as it manages and coordinates the activities
within the computer
• Operating systems perform basic tasks, such as
– recognizing input from input devices,
– sending output to output devices,
– keeping track of files and directories on the disk, and
– controlling peripheral devices such as disk drives and
printers
• Most commonly used operating systems include
Microsoft Windows, MS-DOS, UNIX, Mac OS, Linux etc.

7. ii) Utility Software
• Utility program performs a very specific task, usually
related to managing system resources
• also called system support software as they provide useful
services to the users
• enhance and extend the operating system’s capabilities
and
• assists in maintaining, managing, and protecting computer
system resources
• Some of the utility software are:
– Backup utilities, Security software, System restore,
Compression utilities, Search utilities, Device drivers,
CD/DVD burners etc

8. Device Driver
• Any device that connects to a computer includes
– associated software that must be installed in order for
the operating system to recognize and communicate
with the device
• allows higher level computer programs to interact with a
hardware device
• acts as a translator between a device and the applications
• come on a CD packaged with the peripheral device, or
• can be downloaded from the manufacturer’s Web site
• Some of the device driver applications are: Interfacing with
Printer, Interfacing with Sound Card, Interfacing with
Webcams, Interfacing with Game Controllers etc.

9. Antivirus
• A computer virus is a software program that causes
damage to the computer system or perform ant
malicious act
• Antivirus software is a computer program that detects,
prevents, removes or takes action to malicious software
programs such as viruses, worms, Trojan horses etc.
• Modern antivirus software attempts to identify malware
by searching computer’s files and memory for virus
signatures
• Some of the popular antivirus is Norton, Kaspersky, Avast
Pro, Avira AVG etc.

10. b) Application software
• are designed and developed for the users in order to
make the day to day use of computers
• Much application software have their own purpose and
functionality
• Eg: word processor, spreadsheet, presentation tools, web
browser, media players etc
• Broadly, there are two types of application software:
– Customized or Tailored Software
– packaged or general software

11. i) Customized or Tailored software/Specific purpose
• software designed to meet the specific requirements of
an organization or individual
• developed on the demand of customer by developers
• Eg: banking software, college MIS, bill processing
software, library management system etc.
ii) Packaged Software/General purpose
• software designed to fulfill the requirements of general
users to perform generalized tasks
• developed and sold on the open market
• Eg: word processors, spreadsheets, presentation
packages, database management systems etc.

12. Functions of Operating System
1. Processor Management
• OS decides which process gets the processor when and
for how much time
• This function is called process scheduling
• An Operating System does the following activities for
processor management:
– Keeps tracks of processor and status of process
– Allocates the processor (CPU) to a process
– De-allocates processor when a process is no longer
required

13. 2. Device Management
• controlling all the computer’s Input/ Output devices
• provides an interface between the devices and the
system
• manages device communication via their respective
drivers
• It does the following activities for device management
– Keeps tracks of all devices
– Decides which process gets the device when and for how
much time
– Allocates the device in the efficient way
– De-allocates devices

14. 3. Memory Management
• locating memory appropriately is vital to improve CPU
utilization and system efficiency
• refers to management of Primary Memory
• An Operating System does the following activities for
memory management:
– Keeps tracks of primary memory, i.e., what part are in use by
whom, what parts are not in use
– decides which process will get memory when and how much
– Allocates the memory when a process requests it to do so and
– de-allocates the memory when a process no longer needs it or
has been terminated

15. 4. Deadlock Prevention
• During processing,
– a situation can arise in which a resource shared by two or more
processes cannot continue because the resource required by one
process is held by the other
• This situation is called deadlock
• Operating system ensures that the above condition does
not hold by carefully allocating resources

16. 5. Command Interpretation
• Operating system
– reads the commands,
– interprets them and
– translates them into a detailed set of instructions that the
computer hardware can understand
6. Security
• By means of password and similar other techniques,
– operating system prevents unauthorized access to device,
programs and data

17. Types of Operating System
1. Batch Processing OS
– jobs with similar need are grouped together and run
as a group on a computer system
2. Real Time Operating System
– Processing must be done within fixed time constraint
– provides quick response time
– considered to function correctly only if it returns the
correct result within any time constraint

18. 3. Single-user OS
– allows only one user to operate at a time eg: Ms-DOS.
– we cannot run another program at same time
– we will have to close the first program, only then we
would be able to work on another program or
software
4. Multi-user OS
– allows simultaneous access to a computer system
through two or more terminals
– ticket reservation system that supports hundreds of
terminal under control of a single program is
controlled by multi-user operating system

19. 5. Multi-tasking OS
– two or more program's can be executed by one user
concurrently on the same computer with one central
processor
– Operating system directs the processor to spend a
predetermined amount of time executing the
instruction for each program one at a time
6. Multi-processing OS
– processing done by two or more processors linked
together to perform work
– simultaneously and precisely at the same time