Identifier in c

Identifier is nothing but a name. In programming language variable name is acting as an identifier. Any name in C language can be represented as identifier, that name can be used to identify the particular things.

Example of identifier:

	a variables name, a function name, a array name
	pointer name, structure, union, enum, label name etc.
    

How to write identifier in C?

In every programming language have their own identifier rules. C language also follow some rules.

Rules for identifier in C:

• Identifier can be upper case letter (A to Z) or lower case letter (a to z) or alphabet + integer.
• We can't start an identifier name with digit and any special symbol, except underscore (_) symbol.
• Identifier are case sensitive.
• We can't use keyword as an identifier.
• There is no limit to write the identifier name.
• All predefine function we can use as an identifier, but it is not recommended, but it is valid.

Example of Valid Identifier:

     int a; int abc; int _xyz; int btn123; int dfg_123;
    

Example of Invalid Identifier:

     int 123; int 12abc; int $xyz; int xyz@;
    

Example of case sensitive Identifier:

	
    int num = 10;
    int Num = 20;
    int NUM = 30;
    

In above example you will see different-different variables and all variables have same name. They are different in just case sensitive way. So the output will be different.