Hardware Reference
In-Depth Information
TABLE 2.1
Measurements of storage
Size
Equals
Example
Byte
8 bits
One character of text.
Kilobyte (KB)
1,024 bytes
A 1,000-character plain text file, or a tiny graphic
(18x18 pixels), such as an icon.
Megabyte (MB)
1,024 KB
×
A 600
600 pixel photograph, or one minute of a music clip.
Gigabyte (GB)
1,024 MB
A full-length audio CD is about 800 MB (4/5 of one
gigabyte); a two-hour DVD movie is about 4 GB.
Terabyte (TB)
1,024 GB
A large business database containing records of all
financial transactions.
Petabyte (PB)
1,024 TB
All the data stored by the taxing authority of a large
country, such as the U.S. Internal Revenue Service.
The various storage types you'll learn about in the rest of this chapter have their own
capacity limitations. Table 2.2 summarizes these.
TABLE 2.2
Maximum storage capacities
Media Format
Largest (as of 2011)
Standard (mechanical) hard drive
3 TB
Solid-state drive
2 TB
USB flash drive
256 GB
Compact flash card
128 GB
CD
900 MB
Blu-ray
50 GB
Double-sided, double-density DVD
17.08 GB
ASCII and Unicode
Disks store data as binary numbers. Each character can be uniquely described by a certain
combination of 1s and 0s. The set of codes that defi nes which character corresponds to
which code is called American Standard Code for Information Interchange (ASCII). It was
developed in the 1960s to achieve some standardization among different types of data-
processing equipment. The numbers and letters familiar to our written language are known
