octal

adj. based on the number 8, of a base of eight (Computers, Electricity)

The octal numeral system, or oct for short, is the base-8 number system, and uses the digits 0 to 7.Octal numerals can be made from binary numerals by grouping consecutive digits into groups of three (starting from the right). For example, the binary representation for decimal 74 is 1001010, which groups into 001 001 010 — so the octal representation is 112. In decimal systems each decimal place is a base of 10 for example, 74 = 7 x 10^1 + 4 x 10^0. since 7 x 10^1 = 70 + 4 x 10^0= 4, 70+4 = 74. In octal numerals each place is a power with base 8 for example 112= 1 x 8^2 + 1 x 8^1 + 2 x 8^0 since 1 x 8^2 = 64 + 1 x 8^1 = 8 + 2 x 8^0 = 2, 112 in octal is equal to 64+8+2 = 74. This is why 112 in octal is equal to 74 in decimal. Octal is sometimes used in computing instead of hexadecimal.
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adj. octal, based on the number 8, of a base of eight (Computers, Electricity)

<mathematics> Base 8. A number representation using the digits 0-7 only, with the right-most digit counting ones, the next counting multiples of 8, then 8^2 = 64, etc. For example, octal 177 is digital 127:
digit weight value 1 8^2 = 64 1* 64 = 64 7 8^1 = 8 7* 8 = 56 7 8^0 = 1 7* 1 = 7 --- 127
Octal system used to be widespread back when many computers used 6-bit bytes, as a 6-bit byte can be conveniently written as a two-digit octal number. Since nowadays a byte is almost always 8-bit long the octal system lost most of its appeal to the hexadecimal system.
For a brief discussion on the word `octal' see hexadecimal.
(1997-06-16)

Adjective
1. of or pertaining to a number system having 8 as its base; "an octal digit"
(pertainym) octal numeration system, octal number system