Copyright Goodheart-Willcox Co., Inc.
12 Introduction to Microsoft Offi fice
hard disk drive is the most common example of a magnetic medium.
A hard disk drive, or hard drive, is a sealed unit that contains a stack of
individual disks, or platters, which are magnetic media that rotate at a
very high speed, as shown in Figure 1-10. Solid-state storage media, such
as fl ash drives, is based on circuitry rather than magnetic media. fl
Read head
Platters
Hellen Sergeyeva/Shutterstock.com
Figure 1-10. A hard disk drive consists of multiple platters. The unit is enclosed, but the cover has been removed
in this photo.
Goodheart-Willcox Publisher
Figure 1-9. Quantities of bytes and approximate storage capacity.
Symbols
Number of
Bytes*
Equivalent Sizes
byte e 1 One character.
kilobyte o (KB) 1 thousand bytes One short letter or memo.
meg ga byte (MB) 1 million bytes A typical high-resolution photo is about 2.5MB.
The information in 40 paperback books (a stack about three feet high) is
about 50MB.
gigabyte a (GB) 1 billion bytes One hour of a feature film is about 1.5GB.
The information in 800 paperback books (a stack about 650 feet high) is
about 20GB.
terabyte a (TB) 1 trillion bytes The information in 800,000 paperback books (a stack about 10 miles high)
is about 1TB.
Library of Congress archives contain 160TB.
petabyte a (PB) 1,000 terabytes Seventy-seven million CDs each containing 700MB is 50PB.
exa ab yte (EB) 1,000 petabytes All words ever spoken by human beings are about 5EB.
zettabyte t (ZB) 1,000 exabytes The information in 174 newspapers received daily by every person on
Earth is about 4ZB.
*Note: there are actually 1,024 bytes in a kilobyte, so these values are rounded.