C++ local variables with the same name as counting variables

#include <iostream>
using namespace std;
do_fun();  // Prototype
int main()/*from w  ww. ja v a 2s .  c  om*/
{
   int ctr;                               // Loop counter.
   for (ctr=0; ctr<=10; ctr++)
   {
      cout << "main()'s ctr is " << ctr << "\n";
   }
   do_fun();                      // Call second function.
   return 0;
}
do_fun()
{
   int ctr;
   for (ctr=10; ctr>=0; ctr--)
   {
      cout << "do_fun()'s ctr is " << ctr << "\n";
   }
   return 0;                            // Return to main().
}