Refers to the base-8 number system, which uses just eight unique symbols (0, 1, 2, 3, 4, 5, 6, and 7). Programs often display data in octal format because it is relatively easy for humans to read and can easily be translated into binary format, which is the most important format for computers. By contrast, decimal format is the easiest format for humans to read because it is the one we use in everyday life, but translating between decimal and binary formats is relatively difficult.
In octal format, each digit represents three binary digits, as shown:
With this table it is easy to translate between octal and binary. For example, the octal number 3456 is 011 100 101 110 in binary.