C #ifndef

« Prev Next »

It is a preprocessor directive checks if the macro is not defined by #define. If yes, it executes the code.

Syntax:

#ifndef
	//code
#endif

Example:

#include <stdio.h>  
#include <string.h>       
#define INPUT  
void main() {  
    char i[20]="Welcome";  
    #ifndef INPUT  
        i[20]="Hello";  
    #else  
        printf("Enter the String of i is:");  
        scanf("%s", &i);  
    #endif         
    printf("The String of i: %s\n", i);  
}
Run ›
« Prev Next »

Quickly Find What You Are Looking For

OnlineTpoint is a website that is meant to offer basic knowledge, practice and learning materials. Though all the examples have been tested and verified, we cannot ensure the correctness or completeness of all the information on our website. All contents published on this website are subject to copyright and are owned by OnlineTpoint. By using this website, you agree that you have read and understood our Terms of Use, Cookie Policy and Privacy Policy.