Difference Between Octet and Byte

Difference Between Octet and Byte

In computing, bit is the basic unit of information. Simply, a bit can be seen as a variable that can take only one of the two possible values. These two possible values are ‘0’ and ‘1’ and interpreted as binary digits. The two possible values could also be interpreted as logical (Boolean) values, which are ‘true’ and ‘false’. Byte is another unit of information used in computing. In the history of computing, the unit byte has stood for representing various storage sizes (typically from 4 to 10 bits), because it is not considered a standardized unit. But, due to heavy use of the term byte to represent eight bits by several major computer architectures and production lines, byte slowly became associated with eight bits. Still, due to the earlier ambiguity, the term Octet was introduced as a standardized unit to represent eight bits. So, as of now, both Byte and Octet are used interchangeably to represent eight bits. Byte is also used as a data type in several programming languages such as C and C++.

What is an Octet?

Octet is an unit of information defined as consisting of eight bits. This is used in computing and telecommunications fields. The word Octet comes from the prefix octo (which means eight) that is found in Greek and Latin. The term Octet is often used in place of the term byte to represent eight bits. This is due to the fact, in the past, the byte was not considered as consisting of eight bits (and the size of byte was ambiguous). But at present, because byte is firmly associated with eight bits, the term byte and octet are used synonymously. However, in legacy systems, where the byte may refer to more or less than eight bits, the term octet is used to represent eight bits (instead of byte).

Various representations such as hexadecimal, decimal or octal number systems are used to express octets. For example, the value of the octet with all 1s is equal to FF an hexadecimal, 255 in decimal and 377 in octal. Very frequent use of octets arise in representing addresses in IP (Internet Protocol) computer network. Typically IPv4 addresses are depicted as four octets delimited by dots (full stops). For example, the representation of highest numbered address is 255.255.255.255 (using 4 octets with all 1s). In Abstract Syntax Notation used in telecommunications and computer networking, an octet string refers to an octet sequence of variable length. In French and Romanian languages, the ‘o’ (lowercase letter o) is the symbol used to represent the unit octet. It is also used with metric prefixes (e.g. ko for kilooctet, which means 1000 octets).

What is a Byte?

A Byte is also a unit of information used in computing. One byte is equal to eight bits. Even though there is no specific reason for choosing eight bits for a byte, reasons such as the usage of eight bits to encode characters in a computer, and the usage of eight or fewer bits to represent variables in many applications played a role in accepting 8 bits as a single unit. The symbol used to represent a byte is capital “B” as specified by IEEE 1541. A byte can represent values from 0 to 255. Byte is also used as a data type in several programming languages such as C and C++.

What is the difference between an Octet and a Byte?

In computing, both Byte and Octet are units of information (which are equal to eight bits) that are often used synonymously. Although both represent eight bits (at present), octet is more preferred over byte in applications, where there may be an ambiguity about the size of the byte due to historical reasons (because byte is not a standardized unit and it was used to represent bits strings of different sizes ranging from 4 to10 in the past). Although byte is used in everyday use, the term octet is preferred within technical publications to mean eight bits. For example, RFC (Request for Comments) published by IETF (Internet Engineering Task Force) frequently use the term octet for describing sizes of protocol parameters of networks. In countries such as France, French Canada and Romania, octet is used even in the common language instead of the byte. For example, megaoctet (Mo) is often used in place of megabyte (MB).

 

作者:Chuck Lu    GitHub