Preprocessor operators in c

There are two operators in c preprocessor:

1. # : This operator is called stringizing operator which convert any argument in the macro function in the string. So we can say pound sign # is string maker. Example

#include<stdio.h>

#define string(s) #s

int main(){

    char str[15]= string(World is our );

    printf("%s",str);

    return 0;

}

Output: World is our

Explanation : Its intermediate file will look like:

int main(){

    char str[15]=”World is our”;

    printf("%s",str);

    return 0;

}

Argument of string macro function ‘World is our’ is converted into string by the operator # .Now the string constant “World is our” is replaced the macro call function in line number 4.

2. ## : This operator is called token pasting operator. When we use a macro function with various argument then we can merge the argument with the help of ## operator. Example

#include<stdio.h>

#define merge(p,q,r) p##q##r

int main(){

    int merge(a,b,c)=45;

    printf("%d",abc);

    return 0;

}

Output : 45

Explanation :

Arguments a,b,c in merge macro call function is merged in abc by ## operator .So in the intermediate file declaration statement is converted as :

int abc = 45;

Preprocessor definitions in c

Preprocessor directive in c

#include directive in c

# define directive in c

Pragma directive in c

Warning directive

Preprocessor operators in c

# if directive in c

#line directive in c

# error directive in c

# elif in c

# ifdef and #endif in c

 # ifndef in c example

#undef in c

What is header file in ?

C preprocessor questions

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