octal

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<mathematics> Number base eight. The octal number representation uses 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 representation used to be widespread back when many computers used six-bit bytes, as six-bits can be conveniently written as a two-digit octal number. Since nowadays a byte is almost always eight bits long, the octal system lost most of its appeal to the hexadecimal system. Octal is still found in the C programming language and its descendents where it is commonly to represent characters, as in 'A' = '\101', 101 being octal for 65, the ASCII character code for 'A'.

For a brief discussion on the word `octal' see hexadecimal.

(2017-12-18)

Nearby terms: OCP « OCR « OCS « octal » Octave » octet » octothorpe

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