APPENDIX FOUR
Digital Information and the Metric System
With the proliferation of computers in audio and video production, familiarity with some of the basic terminology of digital computing and the metric system is necessary.
Computers process information in binary digital form. The smallest unit of measure is a bit, which is an abbreviation for binary digit. Each bit has two possible values: 0 (off) and 1 (on). A byte is eight bits, or 28, and contains 256 discrete values:
28 = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 256
The metric number system is used for counting, because it easily deals with very large numbers. The metric system uses the following prefixes:
kilo (k) = 1,000 (thousand)
mega (M) = 1,000,000 (million)
giga (G) = 1,000,000,000 (billion)
tera (T) = 1,000,000,000,000 (trillion)
This system makes it easier to describe large phenomena. For example, the bandwidth of broadcast television is 6 MHz (six megahertz). This is a more economical way to describe 6,000,000 Hz (six million hertz).
Because the metric system is built on a base of 10 and computers count with binary numbers, values in the computer world differ slightly from the pure metric numbers above. As a result,
1 kilobyte = 210 bytes = 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 × 2 = 1,024 bytes (not 1,000)
Consequently,
1 megabyte = 1,024 kilobytes
1 gigabyte = 1,024 megabytes
1 terabyte = 1,024 gigabytes