An octal representation is a number written using Base 8. Each digit may have only one of eight possible values (0 through 7). In computing, octal representations are most often encountered in the context of file system permissions where three or four digit octal numbers are used to denote the access permissions of the user, group and others.

The octal representation of the positive integers is the same as decimal up until the eight digit:

• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 10 (in the decimal system, 8)

All positive integers (and 0) may be written in octal representation.

Appending a zero to the right-hand side of a binary representation multiplies it by 8.