Identifiers in C

Identifier define to name given to entities such as variables, functions, structures etc.

See in Example.

int a;
double accountBalance;

Here a and accountBalance is identifiers.

Here int is keyword

Rules for Identifiers

An identifier can have letters (both uppercase and lowercase letters), digits and underscores..
The first letter of an identifier should be either a letter or an underscore.
Commas or blank spaces cannot be specified within an identifier.
Keywords cannot be represented as an identifier.

Keyword	Identifier
Keyword is a pre-defined word.	The identifier is a user-defined word
It must be written in a lowercase letter.	It can be written in both lowercase and uppercase letters.
Its meaning is pre-defined in the c compiler.	Its meaning is not defined in the c compiler.
It is a combination of alphabetical characters.	It is a combination of alphanumeric characters.
It does not contain the underscore character.	It can contain the underscore character.

Example:

int main()
{
    int a=5;
    int A=10;
    printf("Value of a is : %d",a);
    printf("\nValue of A is :%d",A);
    return 0;
}

Output

Value of a is : 5
Value of A is :10