Multiples of bytes  


 
Orders of magnitude of data 
The kilobyte is a multiple of the unit byte for digital information.
The International System of Units (SI) defines the prefix kilo as 1000 (10^{3}); per this definition, one kilobyte is 1000 bytes.^{ [1] } The internationally recommended unit symbol for the kilobyte is kB.^{ [1] }
In some areas of information technology, particularly in reference to digital memory capacity, kilobyte instead denotes 1024 (2^{10}) bytes. This arises from the prevalence of powers of two in memory circuit design.
In the International System of Units (SI) the prefix kilo means 1000 (10^{3}); therefore, one kilobyte is 1000 bytes. The unit symbol is kB.
This is the definition recommended by the International Electrotechnical Commission (IEC).^{ [2] } This definition, and the related definitions of the prefixes mega (1000000), giga (1000000000), etc., are most commonly used for data transfer rates in computer networks, internal bus, hard drive and flash media transfer speeds, and for the capacities of most storage media, particularly hard drives,^{ [3] } flashbased storage,^{ [4] } and DVDs. It is also consistent with the other uses of the SI prefixes in computing, such as CPU clock speeds or measures of performance.
The IEC 8000013 standard uses the term 'byte' to mean eight bits (1 B = 8 bit). Therefore, 1 kB = 8000 bit. One thousand kilobytes (1000 kB) is equal to one megabyte (1 MB), where 1 MB is one million bytes.
The kilobyte has traditionally been used to refer to 1024 bytes (2^{10} B).^{ [5] }^{ [6] }^{ [7] } The usage of the metric prefix kilo for binary multiples arose as a convenience, because 1024 is approximately 1000.^{ [8] }
The binary interpretation of metric prefixes is still prominently used by the Microsoft Windows operating system.^{ [9] } Metric prefixes are also used for randomaccess memory capacity, such as main memory and CPU cache size, due to the prevalent binary addressing of memory.
The binary meaning of the kilobyte for 1024 bytes typically uses the symbol KB, with an uppercase letter K. The B is often omitted in informal use. For example, a processor with 65,536 bytes of cache memory might be said to have "64 K" of cache. In this convention, one thousand and twentyfour kilobytes (1024 KB) is equal to one megabyte (1 MB), where 1 MB is 1024^{2} bytes.
In December 1998, the IEC addressed such multiple usages and definitions by creating prefixes such as kibi, mebi, gibi, etc., to unambiguously denote powers of 1024.^{ [10] } Thus the kibibyte, symbol KiB, represents 2^{10} bytes = 1024 bytes. These prefixes are now part of the International System of Quantities. The IEC further specified that the kilobyte should only be used to refer to 1000 bytes.
A binary prefix is a unit prefix for multiples of units in data processing, data transmission, and digital information, notably the bit and the byte, to indicate multiplication by a power of 2.
The gigabyte is a multiple of the unit byte for digital information. The prefix giga means 10^{9} in the International System of Units (SI). Therefore, one gigabyte is one billion bytes. The unit symbol for the gigabyte is GB.
Giga ( or ) is a unit prefix in the metric system denoting a factor of a shortscale billion or longscale milliard (10^{9} or 1000000000). It has the symbol G.
Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (10^{3}). It is used in the International System of Units, where it has the symbol k, in lower case.
The kilobit is a multiple of the unit bit for digital information or computer storage. The prefix kilo (symbol k) is defined in the International System of Units (SI) as a multiplier of 10^{3} (1 thousand), and therefore,
The megabyte is a multiple of the unit byte for digital information. Its recommended unit symbol is MB. The unit prefix mega is a multiplier of 1000000 (10^{6}) in the International System of Units (SI). Therefore, one megabyte is one million bytes of information. This definition has been incorporated into the International System of Quantities.
The mebibyte is a multiple of the unit byte for digital information. The binary prefix mebi means 2^{20}; therefore one mebibyte is equal to 1048576bytes, i.e., 1024 kibibytes. The unit symbol for the mebibyte is MiB.
The gibibyte is a multiple of the unit byte for digital information. The binary prefix gibi means 2^{30}, therefore one gibibyte is equal to 1073741824bytes = 1024 mebibytes. The unit symbol for the gibibyte is GiB. It is one of the units with binary prefixes defined by the International Electrotechnical Commission (IEC) in 1998.
The tebibyte is a multiple of the unit byte for digital information. It is a member of the set of units with binary prefixes defined by the International Electrotechnical Commission (IEC). Its unit symbol is TiB.
The kibibyte is a multiple of the unit byte for digital information. The binary prefix kibi means 2^{10}, or 1024; therefore, 1 kibibyte is 1024 bytes. The unit symbol for the kibibyte is KiB.
The megabit is a multiple of the unit bit for digital information. The prefix mega (symbol M) is defined in the International System of Units (SI) as a multiplier of 10^{6} (1 million), and therefore
A unit prefix is a specifier or mnemonic that is prepended to units of measurement to indicate multiples or fractions of the units. Units of various sizes are commonly formed by the use of such prefixes. The prefixes of the metric system, such as kilo and milli, represent multiplication by powers of ten. In information technology it is common to use binary prefixes, which are based on powers of two. Historically, many prefixes have been used or proposed by various sources, but only a narrow set has been recognised by standards organisations.
File size is a measure of how much data a computer file contains or, alternately, how much storage it consumes. Typically, file size is expressed in units of measurement based on the byte. By convention, file size units use either a metric prefix or a binary prefix.
IEEE 15412002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing.
The zebibyte is a multiple of the unit byte for digital information. It is a member of the set of units with binary prefixes defined by the International Electrotechnical Commission (IEC). Its unit symbol is ZiB.
ISO 80000 or IEC 80000 is an international standard introducing the International System of Quantities (ISQ). It was developed and promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).
The JEDEC memory standards are the specifications for semiconductor memory circuits and similar storage devices promulgated by the Joint Electron Device Engineering Council (JEDEC) Solid State Technology Association, a semiconductor trade and engineering standardization organization.
In telecommunications, datatransfer rate is the average number of bits (bitrate), characters or symbols (baudrate), or data blocks per unit time passing through a communication link in a datatransmission system. Common data rate units are multiples of bits per second (bit/s) and bytes per second (B/s). For example, the data rates of modern residential highspeed Internet connections are commonly expressed in megabits per second (Mbit/s).
This timeline of binary prefixes lists events in the history of the evolution, development, and use of units of measure for information, the bit and the byte, which are germane to the definition of the binary prefixes by the International Electrotechnical Commission (IEC) in 1998.
In computing and telecommunications, a unit of information is the capacity of some standard data storage system or communication channel, used to measure the capacities of other systems and channels. In information theory, units of information are also used to measure the entropy of random variables and information contained in messages.