The document provides an overview of computer software, highlighting the essential role of software in enabling hardware functionality as an interface for users. It categorizes software into system software (including operating systems and utility software) and application software (general and specific purpose), detailing their functions and examples. The document also explains the operating system's responsibilities, such as process management, device management, memory management, and security, alongside different types of operating systems like batch processing, real-time, single-user, multi-user, multi-tasking, and multi-processing.

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