Measuring Disk Storage Capacity
| Unit | Equivalent number of bytes | What you might measure |
|---|---|---|
| 1 byte | 8 bits* | a character |
| 1 kilobyte | 1,000 bytes | email message |
| 1 megabyte | 1,000,000 bytes | textbook |
| 1 gigabyte | 1,000,000,000 bytes | bookstore |
| 1 terabyte | 1,000,000,000,000 bytes | university library |
| 1 petabyte | 1,000,000,000,000,000 bytes | future WWW |
| 1 exabyte | 1,000,000,000,000,000,000 bytes | ? |
| 1 zettabyte | 1,000,000,000,000,000,000,000 bytes | ? |
| 1 yottabyte | 1,000,000,000,000,000,000,000,000 bytes | ? |
The bit is physically a transistor or capacitor in a memory cell, a magnetic domain on disk or tape, a reflective spot on optical media or a high or low voltage pulsing through a circuit. Groups of bits make up storage units in the computer, called characters, bytes, or words, which are manipulated as a group.
The most common is the byte, made up of eight bits and equivalent to one alphanumeric character. [Source: TechEncyclopedia]