Octal Number System

The octal number system has a radix of 8 and has eight different digits. The higher-order numbers are expressed as a combination of eight digits.  The digits used are 0, 1, 2, 3, 4, 5, 6 and 7. The next 10 numbers that follow ‘7’, for example, would be 10, 11, 12,
13, 14, 15, 16, 17, 20 and 21.  The place values for the
different digits in the octal number system are,

For integer value: 8^0, 8^1, 8^2, 8^3, 8^4 etc.  8−1, 8−2,
For fractional value: 8^-1, 8^2, 8^−3 etc.

In the octal number system, 7’s and 8’s complements are used. The 7’s complement of octal number is obtained by subtracting each octal digit from 7.  e.g. 7’s complement of (123)8 would be (654)8. The 8’s complement is obtained by adding ‘1’ to the 7’s complement. The 8’s
complement of (123)8 would be (655)8.

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