OCTET (COMPUTING)

In computing, an 'octet' is a grouping of eight bits.
In France, French Canada and Romania, the word ''octet'' usually means byte; a megabyte (MB) is called a ''megaoctet'' in France, Romania and also French Canada. Bit and Byte are homophones in the French language.
''Octet'', with the only exception noted below, always refers to an entity having exactly eight bits. As such, it is often used where the term ''byte'' might be ambiguous. For that reason, computer networking standards almost exclusively use ''octet''.

Contents

Normalization

Exception

Origin

Normalization

Octets can be use with two different set of prefixes, power of 2 set and SI set. The power of 2 prefix was normalized by the International Electrotechnical Commission in 1998.

★ kibi for « 'ki'lo 'bi'nary » ;

★ mebi for « 'me'ga 'bi'nary » ;

★ gibi for « 'gi'ga 'bi'nary » ;

★ tebi for « 'te'ra 'bi'nary » ;

1 'kibioctet' (Kio)	= 210 octets	= octets
1 'mebioctet' (Mio)	= 220 octets	= Kio	= octets
1 'gibioctet' (Gio)	= 230 octets	= Mio	= octets
1 'tébioctet' (Tio)	= 240 octets	= Gio	= octets
1 'pebioctet' (Pio)	= 250 octets	= Tio	= octets
1 'exbioctet' (Eio)	= 260 octets	= Pio	= octets
1 'zebioctet' (Zio)	= 270 octets	= Eio	= octets
1 'yobioctet' (Yio)	= 280 octets	= Zio	= octets

The SI prefixes kilo, mega, giga, tera, etc., stay the same for all the SI units; based on power of 10.
In this case:

1 'kilooctet' (Ko)	= 103 octets	= octets
1 'megaoctet' (Mo)	= 106 octets	= ko	= octets
1 'gigaoctet' (Go)	= 109 octets	= Mo	= octets
1 'teraoctet' (To)	= 1012 octets	= Go	= octets
1 'petaoctet' (Po)	= 1015 octets	= To	= octets

Exception

A group of three bits is also sometimes called an octet, because it can represent eight possible values. It is used this way, for instance, for the group of basic permission bits (''read'', ''write'', ''execute'') of many filesystems for Unix-like platforms.

Origin

The word 'octet' comes from the Latin and Greek numerical prefix octo, meaning eight.