The error is adding Two pointers isn't alowed in C/C++.
The compiler imlicitly treats "SAM" as const char*. We need 
to write a function with "explicit" keyword declaration like

explicit  char * Add (const char* x1, const char* x2) 
{
  // check for null pointers.
  // allocate strlen(x1)+strlen(x2)+1 using malloc 
  // say    char*a1 = malloc...;
  // check if malloc returns null..take corrective actions

  // strcpy (a1, x1);
  // strcat (a1, x2);
  //strcat (a1, '\0');

  return a1; // ask the caller to free the memory allocated
  //  for a1

}

since this function is writen explicit the compiler will 
invoke this function and not call the default template 
function.
this is what appears to me. haven't coded and verified.

// Regards, SADIQ