C #if in C Language
Categories: C language
The #if preprocessor directive evaluates the expression or condition. If condition is true, it executes the code otherwise #elseif or #else or #endif code is executed.
Syntax:
#if expression
//code
#endif
Syntax with #else:
#if expression
//if code
#else
//else code
#endif
Syntax with #elif and #else:
#if expression
//if code
#elif expression
//elif code
#else
//else code
#endif
C #if example
Let's see a simple example to use #if preprocessor directive.
#include <stdio.h>
#include <conio.h>
#define NUMBER 0
void main() {
#if (NUMBER==0)
printf("Value of Number is: %d",NUMBER);
#endif
getch();
}
Output:
Value of Number is: 0
Let's see another example to understand the #if directive clearly.
#include <stdio.h>
#include <conio.h>
#define NUMBER 1
void main() {
clrscr();
#if (NUMBER==0)
printf("1 Value of Number is: %d",NUMBER);
#endif
#if (NUMBER==1)
printf("2 Value of Number is: %d",NUMBER);
#endif
getch();
}
Output:
2 Value of Number is: 1