In number system modern method of representing numbers symbolically is based on positional notations.
In this method, each number is represented by a string of symbols where each symbol is associated with a specific weight depending upon its positions. The total number of different symbols which are used in a particular number system is called the base or radix of the system and the weight of each position of a particular number is expressed as a power of the base. When a number is formed with the combination of the symbols, each symbol is then called a digit and the position of each symbol is referred to as the digit position.
Thus if a number system has symbols starting from 0, and the digits of the system are 0, 1, 2, ….. (r – 1) then the base or radix is r. If a number D of this system be represented by
D = d₀ d₀ ……. d₀…….. d₁ d
then the magnitude of this number is given by
|D| = dn-1 rn-1 + dn-2 rn-2 + …… di ri + …… d1 r1 + d0 r0
Where each d₀ ranges from 0 to r – 1, such that
0 ≤ d₀ ≤ r – 1, i = 0, 1, 2 …… (n – 1).
The digit at the extreme left has the highest positional value and is generally called the Most Significant Digit, or in short MSD; similarly, the digit occupying the extreme right position has the least positional value and is referred to as the Least Significant Digit or LSD.