Computers come in many varieties, from the tiny computers built into household appliances, to the astounding supercomputers that have helped scientists map the human genome. But no matter how big it is or how it is used, every computer is part of a system. A complete computer system consists of four parts
The mechanical devices that make up the computer are called hardware. Hardware is any part of the computer you can touch. A computer’s hardware consists of interconnected electronic devices that you can use to control the computer’s operation, input, and output. (The generic term device refers to any piece of hardware.)
Software is a set of instructions that makes the computer perform tasks. In other words, software tells the computer what to do. (The term program refers to any piece of software.) Some programs exist primarily for the computer's use to help it perform tasks and manage its own resources. Other types of programs exist for the user, enabling him or her to perform tasks such as creating documents. Thousands of different software programs are available for use on personal computers.
Data consist of individual facts or pieces of information that by themselves may not make much sense to a person. A computer’s primary job is to process these tiny pieces of data in various ways, converting them into useful information. For example, if you saw the average highway mileages of six different cars, all the different pieces of data might not mean much to you. However; if someone created a chart from the data that visually compared and ranked the vehicles’ mileages, you could probably make sense of it at a glance. This is one example of data being processed into useful information.
People are the computer operators, also known as users. It can be argued that some computer systems are complete without a person’s involvement; however, no computer is totally autonomous. Even if a computer can do its job without a person sitting in front of it, people still design, build, program, and repair computer systems. This lack of autonomy is especially true of personal computer systems, which arc the focus of this book and are designed specifically for use by people.