Software is a set of computer programs which does some tasks in the system. The software runs on the hardware of the system and is intangible. WebPages, desktop applications, video games and other products are all software developed using scripting or programming languages. Assembly language is also used to develop software. The operating system in turn is software called system software. Other type of software includes application software, middleware, firmware and testware. Most of the software products may show platform specificity. Based on the license, there are open source software and proprietary software. An open source software can be modified and redistributed by anyone.