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Computer Memory Definitions

What is a Kilobyte? Megabyte? Gigabyte? Terabyte? Petabyte? Exabyte? Zettabyte? Yottabyte?

SUMMARY: This tip defines the following computer memory terms: kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte, and yottabyte.

Computers and storage mechanisms (CD-ROMs, hard drives, USB flash drives, DVD-ROMs, Blu-ray Discs, etc.) need to hold much larger values than what a byte can hold (0-255). Thus, the terms kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte, and yottabyte were created to represent such large amounts of information.

The definition of a kilobyte (KB) is 1,024 bytes; however many people think of it as 1,000 bytes.

The definition of a megabyte (MB) is 1,024 kilobytes; however many people think of it as 1,000 kilobytes.

The definition of a gigabyte (GB) is 1,024 megabytes; however many people think of it as 1,000 megabytes.

The definition of a terabyte (TB) is 1,024 gigabytes; however many people think of it as 1,000 gigabytes.

The definition of a petabyte (PB) is 1,024 terabytes; however many people think of it as 1,000 terabytes.

The definition of an exabyte (EB) is 1,024 petabytes; however in some number systems it would be 1,000 petabytes.

The definition of a zettabyte (ZB) is 1,024 exabytes; however in some number systems it would be 1,000 exabytes.

The definition of a yottabyte (YB) is 1,024 zettabytes; however in some number systems it would be 1,000 zettabytes.

Why the confusion? There are two numbering systems in play. Strictly in "computerese", a base 2 system is in play, so that one kilobyte is 2 to the power of 10 bytes, or 1024 kilobytes. However, many hardware manufacturers, including hard drive manufacturers think of a kilobyte as only 1,000 bytes, or 10 to the power of 3 bytes.

This is the same with megabytes, gigabytes, terabytes, petabytes, exabytes, zettabytes, and yottabytes, and that is one reason why when you buy a hard drive with, for example, one terabyte, you may not be getting exactly the amount of storage room that you think!

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The MalekTips website was created in 1998 by Andrew Malek of Envision Programming. The page's goal is to freely disperse computer-related tips, hints, and informative articles. Tips are organized to be easy to find, and are presented clearly, in easy-to-understand language. MalekTips also provides information and links to public-domain, open source, freeware, shareware, and commercial software available for download.