Gigabyte (GB) is the commonly used size specification for the storage capacity of, for example, a hard disk, a DVD or a tape drive. Giga is a prefix based on the decimal system: 10exp9, or 1 billion.
Since the byte refers to the exponentiation of the dual system, one billion bytes correctly corresponds to a storage capacity of 2exp30 bytes. This size is called gibibyte (GiB) in the NISTsystem of units because the absolute value is 1,073,741,824 bytes or 1,099,511,727,776 bytes or 1,048,576 kilobytes
(KB), which is different from the absolute value of gigabyte (GB), which is 1,000,000,000 bytes.