lesson A   Computer functions

Objectives

After completing this lesson you should be able to:

• Identify the five major functions that all computers perform—data input, output, processing, storage, and retrieval—and provide examples of each
• Describe how computers store information and distinguish between bits and bytes
• Identify common bit and byte abbreviations and perform simple bit and byte arithmetic

Basic computer functions

All computers, from the smallest hand held computer to the largest supercomputer, perform the same basic functions with digital information. Those functions are:

• Input—typing characters at a keyboard, moving the mouse around the screen or speaking to a computer
• Output—displaying characters or pictures on the screen, printing a research paper, or sending an e-mail message
• Process—calculating the square root of a number, sorting a list of names, or producing a three-dimensional image
• Store—saving your research paper or resume, keeping track of your credit card purchases, or archiving digital pictures of your relatives
• Retrieve—recalling a list of addresses or business contacts

Computers perform these five fundamental functions in different ways and at different speeds, but they all use digital data to perform the tasks.

What does digital mean?

Computers store information using bits and bytes. A bit, short for binary digit, is either a 0 or a 1. It's the smallest piece of information in the binary number system used by computers. Bits are normally combined in groups of eight to form bytes. A byte is one character. For example, the word information contains eleven characters or bytes of data.

A special coding scheme called ASCII is used to combine bits and bytes into characters that we recognize. For example, in ASCII code the letter a is represented in bits by 01100001. This binary number is equivalent to 97 in the decimal system and is the ASCII code for a. Fortunately, you don't have to know binary arithmetic or the ASCII codes for each character to be productive on a computer. If you did, you probably wouldn't be online now. However, it is useful to know what bits and bytes are because they appear everywhere in computing.

A computer can now store millions and billions of bytes of information in its memory and on its hard disk. The table below shows common prefixes and abbreviations used with bits and bytes. In the last column, notice that abbreviations referring to bits use a lowercase b and byte abbreviations use an uppercase B.

Bit and Byte Prefixes and Abbreviations

Speed on computer networks and modems is usually measured in bits. Computer memory and storage are normally measured in bytes. For example, a high-end laptop computer can store 6 GB (6 billion bytes or characters of information). It also probably has a modem that can send information on the Internet at a speed of 56 Kb per second. Remember, B in an abbreviation means Bytes and b means bits.

Lesson A, page 1 of 2

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