1. System Software:
System software or operating system is the software used by your computer to translate inputs from various sources into a language which a machine can understand. Basically, the OS coordinates the different hardware components of a computer. There are many OS in the market.

The most popular OS are from the stable of Microsoft. We have all heard, used and wondered at the Windows software, which is an OS. Starting with Windows, Microsoft has migrated to Vista, its latest offering in the market.

It may come as a surprise to you that there are other operating systems used by others. Among these UNIX is used for large office setups with extensive networking. XENIX is a software which has now become redundant. HP -UX and AIX are some operating systems used by HP computers. Apache OS is quite popular with web servers. IBM still uses proprietary operating systems for its main frames. Proprietary systems are generally built with the help of a variant of UNIX operating system.

2. Application Software:
A normal user rarely gets to see the operating system or to work with it. But all of us are familiar with application software which we must use to interact with our computers. Popular examples of application software are the Microsoft Office suite which includes Word, Excel and PowerPoint.

We have used these applications extensively. Internet Explorer, Mozilla Firefox is two applications used to access the internet. E-mail software like Outlook Express is used to manage Emails. It is obvious that all software utilized for working on a computer is classified as application software. In fact all user interfaces are an application. The anti-virus is an application and so is the Media player.

3. Programming Languages:
Now this is a kind of computer software which is used exclusively by computer programmers. Unless we are also programmers, we are unlikely to come across programming languages. A simple way to understand programming languages is to think of them as bricks which can be used to create applications and operating system.

C++, Java and Simlab are some popular programming languages. Generally Java is used for internet applications. C++ is a language of professional developers and used extensively in developing operating systems. PHP is another language used for internet applications. There is a new class of languages which are being utilized for the mobiles. These are light weight, modular languages which are used to design mobile applications.

Computer software falls under three basic categories; System software or operating system, application software and programming languages. We usually use applications on a day to day basis. These applications are themselves created using programming languages.