Computer Software

A complete notes on Computer Software for BCA, BIT and BIM. Topic: computer software, system software, utility software, application software,operating system,types of operating system,function of operating system, batch operating system,network operating system, real time operating system, distributed operating system, open source software, malicious software, computer virus, worms, trojan horse

Computer Software

Computer software

Computer needs both hardware and software for it’s proper functioning. Computer software is a collection of data or programs that tells computer how to perform a task.

A program is a set of instruction which performs specific tasks. Programs are coded in different programming languages.

Types of Software

  1. System Software
  2. Utility software
  3. Application software

System Software

System software provides basic functionality to the computer. It is required for the working of computer itself. It provides environment for other types of software to work by co ordinating with computer hardware. It acts as an interface between user, application and computer hardware.

Example: Operating system, device drivers etc.

Utility software

Utility software are those software that helps in maintenance of computer. Anti-virus protects computer from viruses. Disk compression helps to compress content of a disk for increasing the capacity of a disk Cryptography helps to encrypt and decrypt files.

Example: Antivirus, disk cleaners, backup utility etc.

Application software

Application software is used to solve or perform specific task or problems. These software are installed as per user need.

Example: MS- Word for writing and editing documents, Photoshop for photo editing, Tally for accounting information etc.

Operating System

Operating system is a system software that acts as a interface between user  and computer hardware. Different application software used by user needs environment for performing task which is provided by operating system.

Example: Linux, Windows, MS-Dos etc.


  1. It provides an environment/platform in which application software can run.
  2. It manages different resources of computer like file storage, memory space, input output devices etc.
  3. It controls and manage execution different programs to prevent errors.
  4. It provides a interface for user in the form of commands or graphical interface.
  5. It provides proper authentication and authorization of computer system and its resources.

Types of operating system


Open Source Operating System

Open source refers to a program or software in which the source code of a software/program is available to the public for use or modification from the orginal without paying any charge.

In open source, the programmer improves the code and do some modification and share the changes within a particular community. Every individual can access those software with it’s source code. Simply, the software which can be used without any charge is free software and the software which can be used and it’s source code is available free of cost is open source software.

Example of open source operating system: Linux, UNIX, Ubuntu etc.


Malicious Software

The software which are made with an intention to harm the computer system are called malicious software.
Example: Virus, Trojan horse etc.


Virus is a destructive program that gets attach to a healthy program itself and starts replicating  to spread across a network. Virus infects only when a program infected with a virus is executed.

Virus harms computer system by corrupting and deleting data or files, changing the functionality of software application, erasing the hard disk etc.

Viruses mostly spreads by downloading files on internet, attachment in email etc.

Example: “I Love You”, ”Melissa” etc.


Worms is also self-replicating software. It uses network and security holes to replicate itself. A worm doesn’t modify a program like a virus, but makes computer slow by consuming the resources of the computer due to replication.

Example: “Code Red”, “Nimda” etc.

Trojan Horse

Trojan horse is a destructive program that acts as something useful but in fact are malicious codes. It doesn’t replicate itself. Trojan horses can corrupt software applications and damages files.