Byte

The byte (symbol: B or o, also known as the octet) is a unit of measurement of the size of information on a computer or other electronic device. A single byte is eight bits. Some early computers used six bits for each byte. The bit is the smallest unit of storage on a computer, a single on/off value.

A single typed ASCII character (for example, 'x' or '8') is stored in one byte. The character is held as a binary number which encodes a text character. To map each number to a character, an agreed code such as EBCDIC or ASCII is needed.  EBCDIC is a character encoding used mainly on mainframe computers. It uses 8 bits per byte. ASCII is another encoding that only uses seven bits. Extended ASCII uses 8 bits to give more types of characters, mostly used on personal computers.

The byte is the smallest useful unit of measure to show how many characters a computer (or electronics device) can hold.  This is useful for things like RAM, or storage devices like USB drives and other types of Flash memory. Sending of data (for a modem or wi-fi) is usually measured in bits, not bytes.

On modern computers, one byte is equal to eight bits. Some early computers used fewer bits for each byte. To tell them apart, computer scientists called an 8 bit byte an octet. In modern usage, an octet and a byte are the same.

Symbol
The symbol for the byte is B. Sometimes a lowercase "b" is used, but this use is incorrect because "b" is actually the IEEE symbol for the bit. The IEC symbol for bit is bit.  For example, "MB" means "megabyte" and "Mbit" means "megabit". The difference is important because 1 megabyte (MB) is 1,000,000 bytes, and 1 megabit (Mbit) is 1,000,000 bits or 125,000 bytes. It's easy to confuse the two, but bits are much smaller than bytes, so the symbol "b" should be used when referring to "bits" and an uppercase "B" when referring to "bytes".

 Names for larger units 
For large data, byte is often used with a binary prefix:
 Kilobyte (kB) (103)/kibibyte (KB) (210)
 Megabyte (MB) (106)/mebibyte (MiB) (220)
 Gigabyte (GB) (109)/gibibyte (GiB) (230)
 Terabyte (TB) (1012)/tebibyte (TiB) (240)
 Petabyte (PB) (1015)/pebibyte (PiB) (250)

The following terms represent even larger units of bytes, but are very rarely used:
 Exabyte (EB) (1018)/exbibyte (EiB) (260)
 Zettabyte (ZB) (1021)/Zebibyte (ZiB) (270)
 Yottabyte (YB) (1024)/Yobibyte (YiB) (280)
Ronnabyte (RB) (1027)/Robibyte (RiB) (290)
Quettabyte (QB) (1030)/Quebibyte (QiB) (2100)

 Byte Chart 
According to the International Electrotechnical Commission (IEC), who sets many computer standards, these charts show how bytes should be referred to.

People who refer to 1 kilobyte as 1,024 bytes, for example, are technically incorrect; 1,024 bytes should be referred to as 1 kibibyte, according to the IEC.  However, using 1024 for kilo and 1048576 for mega, etc. was widely practiced before the IEC standards were set in 1998. There is some confusion and mixing of terms in the marketplace. Computer memory is still referred to in powers of 2, so 1KB of memory is 1024 bytes, whereas in computer data storage powers of 10 are used, so 1KB is 1000 bytes.

"kilo-" = 1,000 
When using standard metric names like "kilo-", "mega-" and "giga-", they should follow the same measure that other metric measurements use, like kilometer (1 kilometer = 1,000 meters), or gigahertz (1 gigahertz = 1,000,000,000 hertz) for example.
 Unit Number Short scale Long scale Scientific,E Notation/ Power of 10 Byte 
(B) 1 1 
byte 1 
byte1*100,1E0 / 100 Kilobyte 
(KB) 1,000 1 
thousand 

bytes 1 
thousand 

bytes1*103,1E3 / 103 Megabyte (MB) 1,000,000 1 
million 

bytes 1 
million 

bytes1*106,1E6 / 106 Gigabyte (GB) 1,000,000,000 1
billion 

bytes 1
billion 

bytes1*109,1E9 / 109 Terabyte 
(TB) 1,000,000,000,000 1
trillion 

bytes 1
trillion 

bytes1*1012,1E12 / 1012 Petabyte 
(PB) 1,000,000,000,000,000 1 
quadrillion 

bytes 1 
quadrillion 

bytes1*1015,1E15 / 1015 Exabyte 
(EB) 1,000,000,000,000,000,000 1 
quintillion 

bytes 1 
quintillion 

bytes1*1018,1E18 / 1018 Zettabyte (ZB) 1,000,000,000,000,000,000,000 1 
sextillion 

bytes 1
sextillion 

bytes1*1021,1E21 / 1021 Yottabyte (YB) 1,000,000,000,000,000,000,000,000 1 
septillion 

bytes 1
septillion 

bytes1*1024,1E24 / 1024 Ronnabyte (RB) 1,000,000,000,000,000,000,000,000,000 1
octillion 

bytes 1
octillion 

bytes1*1027,1E27 / 1027 Quettabyte (QB) 1,000,000,000,000,000,000,000,000,000,000 1
nonillion 

bytes 1
nonillion 

bytes1*1030,1E30 / 1030

"kibi-" = 1,024 
Since computers are very complex digital devices that are based on the binary numeral system rather than the commonly-used decimal numeral system or binary coded decimal system, there are many situations where the standard metric system does not work well, particularly with memory sizes for a computer or storage device.  If a memory or storage device uses a binary number for addresses, the number of different positions to be accessed (the size of the memory) can be expressed as a power of 2, rather than a power of 10.  

UnitNumberMaths Byte 
(B) 1 20 bytes Kibibyte 
(KiB) 1,024  210 bytes Mebibyte 
(MiB) 1,048,576  220 bytes Gibibyte 
(GiB) 1,073,741,824  230 bytes Tebibyte 
(TiB) 1,099,511,627,776  240 bytes Pebibyte 
(PiB) 1,125,899,906,842,624 250 bytes  Exbibyte 
(EiB) 1,152,921,504,606,846,976  260 bytes Zebibyte 
(ZiB) 1,180,591,620,717,411,303,424  270 bytes Yobibyte 
(YiB) 1,208,925,819,614,629,174,706,176  280 bytes Robibyte 
(RiB) 1,237,940,039,285,380,274,899,124,224 290 bytes Quebibyte 
(QiB) 1,267,650,600,228,229,401,496,703,205,376 2100 bytes

 References 

Category:Computer science
Category:Units of information