Lesson 1: The Three Stages of Computing

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In this lesson, we discuss the three stages of computing and how they relate to the constituent parts that make up the modern personal computer.

After this lesson, you will be able to:

• Describe the three stages of computing.

Estimated lesson time: 5 minutes

A modern computer looks like a complicated device. It is constructed of many hardware components connected with what seem to be miles of interwoven wires. Despite this apparent complexity, however, a computer, just like a calculator, handles information in three stages: input, processing, and output. (See Figure 3.1.) Each piece of hardware can be classified in one (and sometimes two) of these three stages. We can also use these three stages to classify any aspect of a computer's operation or the function of any of its components. During the troubleshooting phase of a repair job, it is often useful to categorize a problem according to which of the three stages it occurs in.

Figure 3.1 Three stages of computing

Input

Input is the first stage of computing. Input refers to any means that moves data (information) from the outside world into the processor. Today's PC can support a wide variety of input devices; keyboards, mouse devices, voice recognition devices, sound cards, modems, scanners, tape drives, CD/DVD drives, and video cameras are some of the most common.

Processing

Processing is the second stage of computing: the actual manipulation of data by the computer. Computers were designed initially as tools to carry out the tedious task of "number crunching" and then, later, to store large amounts of often redundant data. Today, computers not only fulfill ever-expanding scientific and business roles, but they also fill our lives with education, entertainment, organization, information processing, and—occasionally—frustration. As we enter this new century, computers have become a necessity of life and are often taken for granted. Even for people who do not own or use a personal computer, they are an increasing part of everyday life. And computer technology hides in many everyday appliances. Microprocessors run most of our mechanical and electronic devices, including cars, cameras, VCRs, microwave ovens, telephones, and the checkout system at the supermarket.

Output

Output is the third stage of computing. All the input and processing in the world won't do us any good unless we can get the information back from the computer in a comprehensible and usable form. Output devices today come in many forms: monitors, printers, fax machines, modems, plotters, CD-recordable discs, sound cards, and more.

Input, Processing, and Output

Whenever you sit down at a computer and run an application—whether it is a game, spreadsheet, database, or word processor—you are an active part of the input, processing, and output operation of that computer. The following table provides some examples.

Application	Function
Word processor	Input: Typing your words. Processing: Formatting the text (such as wordwrap and fonts). Output: Storing the text and allowing you to retrieve or print it.
Spreadsheet	Input: Typing or providing numbers (such as sales figures). Processing: Applying one or more formulas to the data. Output: Displaying the results of the calculation in numeric or graphical form.
Database	Input: Typing information into a data form. Processing: Indexing and storing the data records. Output: Producing reports showing selected data records.
Game	Input: Moving your chess piece. Processing: Computer calculating how to respond to your move. Output: Computer making a move.

Lesson Summary

The following points summarize the main elements of this lesson:

• All computer hardware can be classified according to its primary function: input, processing, or output.
• Any time you sit down at a computer and run an application, you are using the input, processing, and output stages of computing.