---
title: 1.22 C Keywords
description: "Keywords are reserved words defined by the C language. They have predefined meanings and cannot be used as identifiers such as variable or function names. ``` #include int main() { int number = 10; if (number > 0) { printf(\"Positive\\n\");…"
url: "https://edcret.in/docs/c-programming/basic-refreshers/1-22-c-keywords/"
updated: "2026-09-06"
category: C Programming / Basic Refreshers
---

# 1.22 C Keywords

Keywords are reserved words defined by the C language. They have predefined meanings and cannot be used as identifiers such as variable or function names.

```
#include <stdio.h>

int main()
{
    int number = 10;

    if (number > 0)
    {
        printf("Positive\n");
    }

    return 0;
}
```

### Example Output

```
Positive
```

### Explanation

The program uses several C keywords:

```
int
if
return
```

Each has a specific language-defined meaning.

For example:

```
int number = 10;
```

uses `int` to specify the type of `number`.

```
if (number > 0)
```

uses `if` to conditionally execute a statement.

```
return 0;
```

uses `return` to terminate the `main()` function and provide its return value.

### C Keywords

The following table lists the keywords defined by the C language through C23:

| Keyword | Keyword | Keyword | Keyword |
| --- | --- | --- | --- |
| `alignas` | `alignof` | `auto` | `bool` |
| `break` | `case` | `char` | `const` |
| `constexpr` | `continue` | `default` | `do` |
| `double` | `else` | `enum` | `extern` |
| `false` | `float` | `for` | `goto` |
| `if` | `inline` | `int` | `long` |
| `nullptr` | `register` | `restrict` | `return` |
| `short` | `signed` | `sizeof` | `static` |
| `static_assert` | `struct` | `switch` | `thread_local` |
| `true` | `typedef` | `typeof` | `typeof_unqual` |
| `union` | `unsigned` | `void` | `volatile` |
| `while` | `_Alignas` | `_Alignof` | `_Atomic` |
| `_BitInt` | `_Bool` | `_Complex` | `_Decimal128` |
| `_Decimal32` | `_Decimal64` | `_Generic` | `_Imaginary` |
| `_Noreturn` | `_Static_assert` | `_Thread_local` | — |

The exact keyword set depends on the C standard being used. Older standards such as C90, C99, C11, and C17 contain fewer keywords than C23.

Keywords cannot be declared as ordinary identifiers:

```
int return = 10;   /* Invalid */
```

A name such as `return_value` is valid because it is an identifier, not the keyword `return`.