Conversion of macros into String literals

The # preprocessor operator converts the argument that follows it into a string literal. The preprocessor operator # can be used only in a function-like macro definition.

#include <stdio.h>

#define PRINT(name) printf("The value of " #name " is %d\n", name)

main()
{
 int abc = 100;

 PRINT(abc);
}

Output: The value of abc is 100
Macro Expansion
--> printf("The value of " #name " is %d\n", name)
--> printf("The value of " "abc" " is %d\n", 100)
--> printf("The value of abc is %d\n", 100)
The unary # operator produces a string from its operand. Adjacent string literals are getting concatenated in above example. If the operand to # contains double quotes or escape sequences, they are also expanded.
Similarly ## operator concatenate two tokens passed in macro to a single token.

#define JOIN(a,b)  a ## b
main()
{
   int myname = 100;
   printf("%d", JOIN(my,name));
}
It will be converted into printf("%d", myname);