An identifier is a name used to identify program elements such as variables, functions, arrays, structures, and other declared entities. C places specific rules on how identifiers can be formed.

#include <stdio.h>

int main()
{
    int student_count = 10;
    int totalMarks = 500;

    printf("Students: %d\n", student_count);
    printf("Total marks: %d\n", totalMarks);

    return 0;
}

Example Output #

Students: 10
Total marks: 500

Explanation #

The names:

student_count
totalMarks

are identifiers used to identify variables.

An identifier can contain:

• Letters (A–Z, a–z)
• Digits (0–9)
• Underscores (_)

An identifier cannot begin with a digit.

Identifier Rules #

C identifiers are case-sensitive:

int value;
int Value;

value and Value are two different identifiers.

Keywords reserved by the C language cannot be used as identifiers. The complete set of C keywords is covered in the next lesson.