Definition:Octal Notation

Definition
Octal is another word for base $8$.

That is, every number $x \in \R$ is expressed in the form:
 * $\displaystyle x = \sum_{j \in \Z} r_j 8^j$

where $\forall j \in \Z: r_j \in \left[{0 .. 7}\right]$.

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