The lowest level form of software which has direct contact with the computer hardware. It manages resources as well as other software programs sitting on top. The operating system takes care of all the low level functions a computer performs and is probably the most complex piece of software in circulation.Software which can normally be bought from stores is called application software. These packages serve infinite purposes and can vary from office applications, like word processors, spreadsheets, payroll systems, account systems, anti-virus applications and database driven software, to games, communication and multimedia applications.

Software applications need to be loaded through a disk or through a network link from an office server or internet. It loads into the computer memory and normally gets installed on the local computer’s internal drive. Once resident there, every time the package is called from the user, it loads into the computer’s memory and execution starts. Some applications remain resident in the computer’s memory for as long as the computer is functioning. These are normally functions forming part of the operating system and other applications like network applications, anti-virus software and device drivers.