Bit

A bit (a contraction of binary digit) is a unit of data that consists of a (0 or 1, also represented on/off and true/false). Groups of 8-bits of data are measured as bytes.

Because of the relationship of bits to bytes (8 bits = 1 byte), it is a significant difference in overall storage quantity should the two nomenclatures be confused. Typically, bytes are used for physical storage (eg. 20 GB capacity), while bits are used for throughput or bandwidth ratings (eg. 400 Mbps transfer rate, or bit rate).

Variations

 * A binary kilobit (Kibit) consists of 1,024 bits ( 210 )
 * A binary megabit (Mibit) consists of 1,024 kilobits, or 1,048,576 bits ( 220 )
 * A binary gigabit (Gibit) consists of 1,024 megabits, or 1,073,741,824 bits ( 230 )
 * A binary terabit (Tibit) consists of 1,024 gigabits, or 1,099,511,627,776 bits ( 240 )
 * A binary petabit (Pibit) consists of 1,024 terabits, or 1,125,899,906,842,624 bits ( 250 )
 * A binary exabit (Eibit) consists of 1,024 petabits, or 1,152,921,504,606,846,976 bits ( 260 )

Starting with iOS 11 and Mac OS X 10.6, Apple stopped using binary values and switched to decimals, causing a "megabyte" to report 1,000,000 bytes instead of 1,048,576 bytes, as had been done in the past. This created an illusion of a slight increase in data capacity (memory and storage).


 * A decimal kilobit (kbit) consists of 1,000 bits ( 103 )
 * A decimal megabit (Mbit) consists of 1,000 kilo bits, or 1,000,000 bits ( 106 )
 * A decimal gigabit (Gbit) consists of 1,000 mega bits, or 1,000,000,000 bits ( 109 )
 * A decimal terabit (Tbit) consists of 1,000 giga bits, or 1,000,000,000,000 bits ( 1012 )
 * A decimal petabit (Pbit) consists of 1,000 tera bits, or 1,000,000,000,000,000 bits ( 1015 )
 * A decimal exabit (Ebit) consists of 1,000 peta bits, or 1,000,000,000,000,000,000 bits ( 1018 )