is that char null terminator is including in the length count

Question

#include 

int main(int argc, char *argv[]) {
   char s[]=\"help\";
   printf(\"%d\",strlen(s));  
}

Why the above output is 4, isn

Answer 1

strlen(const char* ptr) returns the length of the string by counting the non-zero elements starting at until reaches zero. So '\0' doesn't count.

I recommend that you consult the reference like link for questions like this.

It's clearly stated as:

 A C string is as long as the number of characters between the beginning 
 of the string and the terminating null character (without including the
 terminating null character itself).