In this lesson, we discuss the three stages of computing and how they relate to the constituent parts that make up the modern PC.
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. On one level this is true, and it is the beneficiary of much development in electronics technology. 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 as working 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.
Input is the first stage of computing, referring to any means that moves data (information) from the outside world into the processor—or from one component of the computer to another. 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 digital cameras are some of the most common.
Processing is the second stage of computing. This is the actual manipulation of data by the computer. Processing on early computers involved the tedious task of "number crunching" and then, later, storing large amounts of often-redundant data. Today, computers process an ever-expanding list of activities, including scientific and business tasks, as well as processing information for education, entertainment, organization, and much more. Computer processing technology also hides in many everyday appliances. Microprocessors run most of our mechanical and electronic devices including cars, cameras, VCRs, microwave ovens, telephones, and even supermarket checkout systems.
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-Rs, sound cards, and more.
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 word wrap 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 |
Keep in mind that this is a short list focusing on human interaction with the machine. The PC often takes information for its own components and processes that data for internal use, as when a drive is accessed or a display adapter sends signals to the monitor.
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.
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