Octal

Numeral systems, bits and Gray code
hex dec oct 3 2 1 0 step
0hex 00dec 00oct 0 0 0 0 g0
1hex 01dec 01oct 0 0 0 1 h1
2hex 02dec 02oct 0 0 1 0 j3
3hex 03dec 03oct 0 0 1 1 i2
4hex 04dec 04oct 0 1 0 0 n7
5hex 05dec 05oct 0 1 0 1 m6
6hex 06dec 06oct 0 1 1 0 k4
7hex 07dec 07oct 0 1 1 1 l5
8hex 08dec 10oct 1 0 0 0 vF
9hex 09dec 11oct 1 0 0 1 uE
Ahex 10dec 12oct 1 0 1 0 sC
Bhex 11dec 13oct 1 0 1 1 tD
Chex 12dec 14oct 1 1 0 0 o8
Dhex 13dec 15oct 1 1 0 1 p9
Ehex 14dec 16oct 1 1 1 0 rB
Fhex 15dec 17oct 1 1 1 1 qA

Octal (base 8) is a numeral system with eight as the base.

In the decimal system, each place is a power of ten. For example:

In the octal system, each place is a power of eight. For example:

By performing the calculation above in the familiar decimal system, we see why 112 in octal is equal to in decimal.

Octal numerals can be easily converted from binary representations (similar to a quaternary numeral system) by grouping consecutive binary digits into groups of three (starting from the right, for integers). For example, the binary representation for decimal 74 is 1001010. Two zeroes can be added at the left: (00)1 001 010, corresponding to the octal digits 1 1 2, yielding the octal representation 112.

The octal multiplication table
× 1 2 3 4 5 6 7 10
1 1 2 3 4 5 6 7 10
2 2 4 6 10 12 14 16 20
3 3 6 11 14 17 22 25 30
4 4 10 14 20 24 30 34 40
5 5 12 17 24 31 36 43 50
6 6 14 22 30 36 44 52 60
7 7 16 25 34 43 52 61 70
10 10 20 30 40 50 60 70 100

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