Question

#include <stdio.h>
#include <stdlib.h>
int main()

{
char *str="Helloworld";
printf("%d",printf("%s",str));
return 0;
}

output of this program is Helloworld10 instead of Helloworld1
from where that miscellaneous zero comes

Answer 1

Why would you like the program to write Helloworld1? What should that 1 come from?
the return value of functions of the printf family is the number of characters outputted (except the final \0 for the variants like sprintf). Helloworld has length 10.