The **`_Static_assert`** is a keyword defined in the *C11* version of C. It evaluates a constant expression at compile-time and compares the result with 0.  

>The `_Static_assert` is available as the macro `static_assert` keyword defined in C11. [Click here](https://www.educative.io/answers/what-is-staticassert-in-c) for more information on
`static_assert.` 


To use the `_Static_assert` keyword, we need to import the `assert.h` header file, as shown below:
```C
#include <assert.h>
```

# Syntax
The `_Static_assert` keyword is declared as follows:


# Parameters
The `_Static_assert` keyword takes two arguments. 

* The expression is an `integer constant expression`

* The message is a `string literal` 

# Return value 
* If the expression equals zero (false), the compiler generates an error and displays the second parameter. 

* If the expression is *not* equal to zero (true), there is no effect on the program. 

# Examples
The following code shows the use of `_Static_assert`. The expression evaluates to true. Hence, the code executes successfully, and there is no effect on the program:

#include <stdio.h>
#include <assert.h>

int main(){
  //Expression evaluated to True 
  _Static_assert (1+1 == 2, "True!");
  
  return 0;
}

In the following example, the expression evaluates to false. Hence, the message in the second parameter is displayed, and the compiler generates an error:

#include <stdio.h>
#include <assert.h>

int main(){
  //Expression evaluated to False 
  _Static_assert (1+3 <= 2, "False!");
  
  return 0;
}

What is _Static_assert keyword in C?

Syntax

Parameters

Return value

Examples