What is use of # and ## operator in c programming language?

What is use of # and ## operator in c programming language?

There are two operators in preprocessor in c:

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. For 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 is:

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. For 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;

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