Need of Software

A computer's hardware, however sophisticated, cannot be spoken to directly. A human user has no way of instructing a processor or a printer in the raw electrical terms those devices understand. This is the gap software exists to fill: the sole purpose of software is to make the computer hardware useful and operational.

Software as the interface

Software knows how to make the different hardware components of a computer work — and, crucially, how to make them communicate with each other as well as with the end user. Since we cannot talk to or instruct the hardware directly, software sits between us and the machine, acting as an interface between human users and the hardware. Every command a user gives passes through software before it ever reaches a physical component, and every result the hardware produces passes back through software before the user sees it.

The three categories of software

Not all software plays the same role. Depending on its mode of interaction with the hardware and the functions it is meant to perform, software is broadly classified into three categories:

• System software — the software that deals with the hardware directly and provides the basic functionality to operate the computer.
• Programming tools — the software used to write and develop other software.
• Application software — the software that serves the specific requirements of end users.

This categorisation is depicted in Figure 1.9, which arranges the categories in layers between the user at the top and the hardware at the bottom. …