# 1 Software

The instructions are brought together in software. Software is a collection of the instructions that tell the computer how to work. In contrast, the physical hardware from which the system is built and actually performs the work is called hardware.

Software can be split into two categories, application software and operating systems. Application software is the name given to programs which enable a computer to perform specific tasks. The program that processes the image in the digital camera is one example; a word processor running on a PC is another.

In computers that are running several application programs, the programs may well be sharing some of the computer’s resources, such as its display or its hard disk. If this is the case then an operating system provides general-purpose software that controls the sharing of resources amongst the various programs, making sure that they are not competing for the same resource. The operating system on a PC makes it possible for, say, information about incoming email to appear on the screen whilst a word processor is running and a document is printing. The operating systems you are most likely to be familiar with in business and in schools is Windows®. There are however many other operating systems, such as macOS on Apple Macs, and iOS on Apple smartphones. The majority of other smartphones use Android as their operating system. Google developed of Android from UNIX, an operating system that is far older than Windows and very popular for back office functions that run at scale and require excellent reliability. For example, UNIX is used on nearly all internet servers.

Very simple computers, such as the one in the kitchen scales, have only one program running and consist of a modest set of resources. In such simple systems the distinction between the operating system and the application program is not clearly defined, and it is not customary to distinguish between them. This is typical of embedded computers, but then they are dedicated to deliver one task. In more complex computers an operating system becomes useful, and in something as complex as a PC it is a crucial component.

In the next section you will look a little more closely at operating systems. Then you will be introduced to how application programs are developed. Finally, you will see a little of a special form of application programming, and how to program for the internet.

OpenLearn - An introduction to computers and computer systems
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