Identifiers are names given to variables, functions, and other user-defined items in a program to uniquely identify them. Identifiers must be different from keywords and other identifiers. They can include letters, digits, and underscores but must begin with a letter or underscore. Common examples of identifiers are variable and function names like roll_no and average. Identifiers are case-sensitive and allow programmers to reference specific program elements like variables during execution.

1. What is
Identifier

2. What is Identifiers
A C identifier refers to name used to identify a variable, function, structures or any
other user-defined item or entity.
Identifier must be unique. They are created to give unique name to a
entity/item/variable name to identify it during the execution of the program
identifier names must be different from keywords. Because Keywords are
predefined, reserved words used in programming .As for Example :You cannot
use double as an identifier because double is a keyword.

3. Identifiers Example
int roll_no;
double percentge_marks;
float average;
Here, roll_no , percentge_marks , average are identifiers.
Here are some another examples of acceptable identifiers
zakir Ram abc movie_name ab_123
myname50 _temp p a666b9 sum avg multi

4. Rules for writing an identifier
 The first letter of an identifier should be either a letter or an underscore.
 A valid identifier can have letters (both uppercase and lowercase letters), digits
and underscores.
 There is no rule on length of an identifier. However, the first 31 characters of
identifiers are significant by the compiler.
 Must not contain white space
 Can not use Keyword as a identifier

5. identifiers in Programming
#include<stdio.h>
int main () {
/* variable definition: */
int variable_1, variable_2;
int variable_3;
variable_1=6;
variable_2=6;
variable_3 = variable_1 + variable_2;
printf("value of c : %d n", variable_3 );
return 0;
}
In this Example identifiers are:
variable_1
variable_2
variable_3
OutPut
value of c : 12
Press any key to continue . . .

6. Thank You