Introduction to Computer Science

A computer system has three main components: hardware, software, and people. The equipment associated with a computer system is called hardware. Software is a set of instructions that tells the hardware what to do. People, however, are the most important component of a computer system - people use the power of the computer for some purpose. In fact, this course will show you that the computer can be a tool for just about anyone from a business person, to an artist, to a housekeeper, to a student - an incredibly powerful and flexible tool.
Software is actually a computer program. To be more specific, a program is a set of step-by-step instructions that directs the computer to do the tasks you want it to do and to produce the results you want. A computer programmer is a person who writes programs. Most of us do not write programs, we use programs written by someone else. This means we are users - people who purchase and use computer software.

Hardware: Meeting the Machine

What is a computer? A six-year-old called a computer "radio, movies, and television combined!" A ten-year-old described a computer as "a television set you can talk to." The ten-year-old's definition is closer but still does not recognize the computer as a machine that has the power to make changes.
A computer is a machine that can be programmed to accept data (input), process it into useful information (output), and store it away (in a secondary storage device) for safekeeping or later reuse. The processing of input to output is directed by the software but performed by the hardware.

To function, a computer system requires four main aspects of data handling: input, processing, output, and storage. The hardware responsible for these four areas operates as follows:

Input devices accept data in a form that the computer can use; they then send the data to the processing unit.
The processor, more formally known as the central processing unit (CPU), has the electronic circuitry that manipulates input data into the information people want. The central processing unit executes computer instructions that are specified in the program.
Output devices show people the processed data-information in a form that they can use.
Storage usually means secondary storage. Secondary storage consists of devices, such as diskettes, which can store data and programs outside the computer itself. These devices supplement the computer's memory, which, as we will see, can hold data and programs only temporarily.