Octal

Base-8 numeral system or octal uses digits from 0 to 7 and can be achieved from grouping consecutive binary digits into groups of 3.

Octal is sometimes used instead of hex as it does not require other symbols as digits, as opposed to the hex system that requires 6 letters.

Numbers in this system is identified from their prefixes, usually a “0″ digit or the letter “q” (can also be a combination of the digit “0″ and lowercase “o” resulting in “0o”). The use of “0o” is to avoid starting an integer value with a string character while the use of “q” avoids confusion between the letter “o” and the digit “0″.