# Definition:Octal Notation

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## Definition

**Octal** is another word for base $8$.

That is, every number $x \in \R$ is expressed in the form:

- $\displaystyle x = \sum_{j \mathop \in \Z} r_j 8^j$

where:

- $\forall j \in \Z: r_j \in \set {0, 1, 2, 3, 4, 5, 6, 7}$

## Also known as

**Octal notation** is also known as **octonary** or **octenary**.

## Historical Note

**Octal notation** was advocated by Emanuel Swedenborg.

**Octal notation** used to be important in the field of computer science, but is less so nowadays, as hexadecimal has proved itself more convenient in general.

## Sources

- 1986: David Wells:
*Curious and Interesting Numbers*... (previous) ... (next): $8$ - 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $8$ - 2014: Christopher Clapham and James Nicholson:
*The Concise Oxford Dictionary of Mathematics*(5th ed.) ... (previous) ... (next): Entry:**octal**