A number system is a set of symbol use to represent a number or helps us for counting purpose. The symbols used in general can be referred as digits(or bits). The number of digits used in a number system is called the base of that number system which is written as subscript. 
Number system can be categorized into two types;
(i) Positional Number system
(ii) Non-Positional Number system

 # Positional Number System
➤ This type of number system has a definite positional weight/value. The value of number depends upon the position they are placed in. 
                                    
We can see that, here same digit at different position holds certain value, 4 at ones represent 4, where is tens represent 40 and that in hundred represents 400, which sums up 400+40+4 to be 444. This type of number system is Positional Number System.
Examples; Decimal Number System, Binary Number System, Octal Number System, Hexadecimal Number System etc.

# Non- Positional Number System
➤ This type of number system has no definite positional weight/value as that of positional number system. They use limited symbols for the representation of number in which each symbol has a value rather than the position they are placed in.
Roman Numbers are the best examples of Non-Positional Number System.