
The **`#if` direction** is a preprocessor used to easily evaluate if-else conditions in the C language. It is the same as the if condition that is widely used in C programming . 
```
#if (expression)  
// given that expression is true, if is executed. 
//code  
#endif  
```
```
#if expression  
//if code  

// instead of else if, we use elif in this directive. 
#elif expression
//elif code  


#else  
//else code

#endif  
```

# Code
Let's look at a simple coding example:

#include <stdio.h>  
#define NUMBER -2 
int main() {
    
#if (NUMBER>0)  
printf("Value of Number greater than 0 is: %d",NUMBER);
#else
printf("Value of Number less than 0 is: %d",NUMBER);

#endif         
 
    return 0;
}

What is the #if directive in C?

The #if directive in C evaluates conditions during preprocessing, similar to runtime if-else, using #elif and #else for branching.