We have already mentioned that computer can handle with two type of signals, therefore, to represent any information in computer, we have to take help of these two signals.
These two signals corresponds to two levels of electrical signals, and symbolically we represent them as 0 and 1.
In our day to day activities for arithmatic, we use the Decimal Number System. The decimal number system is said to be of base, or radix 10, because it uses ten digits and the coefficients are multiplied by power of 10.
A decimal number such as 5273 represents a quantity equal to 5 thousands plus 2 hundres, plus 7 tens, plus 3 units. The thousands, hundreds, etc. are powers of 10 implied by the position of the coefficients. To be more precise, 5273 should be written as:
However, the convention is to write only the coefficient and from their position deduce the necessary power of 10.
In decimal number system, we need 10 different symbols. But in computer we have provision to represent only two symbols. So directly we can not use decimal number system in computer arithmatic.