In binary r bits can represent symbols. e.g. 3 bits can represent up to 8 symbols, 4 bits for 16 symbols etc. For N symbols to be represented, the minimum number of bits required is the lowest integer 'r'' that satisfies the relationship.

e.g. if N = 26, minimum r is 5 since .

Octal Numbers

Digital systems operate only on binary numbers. Since binary numbers are often very long, two shorthand notations, octal and hexadecimal, are used for representing large binary numbers. Octal systems use a base or radix of 8. Thus it has digits from 0 to 7 (r-1). As in the decimal and binary systems, the positional valued of each digit in a sequence of numbers is fixed. Each position in an octal number is a power of 8, and each position is 8 times more significant than the previous position.