A Numeral system is used to represent numbers using a pre-defined list of symbols. The simplest numeral system is Binary which comprises of only two such symbols: 0 and 1. These two numbers can be used to represent numbers of any size. For example, decimal numbers can be represented as follows in Binary:-
Computers use different numeral bases. A digital computer only deals with 0s and 1s, so binary (base 2) is used at the simplest level. Computers group binary digits together and there Hexadecimal (base 16) is used. When systems such as the PDP-8, ICL 1900 and IBM mainframes were employed, Octal numbers (base 8) became widely used. Three binary digits are grouped together to create an Octal number. Us humans, on the other hand, prefer decimal number system for our day to day operations. Similarly, there are usages for various other number bases.