The binary number system, also called as base-2 number system, is a numbering system that represents numeric values using two unique digits, 0 and 1.
Each of the binary digits, 0 or 1, is called a "bit" (an acronym for binary digit).
Binary counting follows the same procedure as decimal counting.
The difference is that, in binary counting, only two digits(0 and 1) are avaliable.
This is explained using 4-digit representation as under;
0100, 0101, 0110, 0111
1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111
The next number is 5-digit number 10000. And so on.
Where ever required, a number is enclosed in parenthesis with a subscript indicating the base of the number system.
Ex: (11)10 is the number 'eleven' in the decimal number system.
(11)2 is a number in the binary number system. Its equivalent in the decimal number system is 'three'.
Similarly, (101)2 is a binary number (whose decimal equivalent is 5), where as (101)10 is the decimal number 'one hundred and one'.