---
title: 1.21 C Identifiers
description: "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 int main() { int student_count = 10; int…"
url: "https://edcret.in/docs/c-programming/basic-refreshers/1-21-c-identifiers/"
updated: "2026-09-06"
category: C Programming / Basic Refreshers
---

# 1.21 C Identifiers

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

| Rule | Valid example | Invalid example |
| --- | --- | --- |
| Can contain letters | `count` | — |
| Can contain digits | `value2` | — |
| Can contain `_` | `total_value` | — |
| Cannot begin with a digit | `value2` | `2value` |
| Cannot contain spaces | `student_count` | `student count` |
| Cannot contain operators | `total_value` | `total-value` |
| Case-sensitive | `count` and `Count` | — |
| Cannot be a keyword | `number` | `int` |

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.