I made this simple code sample, to show the erro:

#include <iostream>

using namespace std;

int main(int argc, char **argv)
{
  auto foo = "Ola mundo";
  auto bar = 15;

  cout << foo << " -> " << bar << endl;

  return 0;
}

and, when I try to build, I got that error:
$dmc main.cpp -I\dm\stlport\stlport
  auto foo = "Ola mundo";
                        ^
main.cpp(7) : Error: need explicit cast to convert
from: char const *
to  : int
--- errorlevel 1

Btw, how to use the auto variables ?

Sounds like C++11 isn't enabled, auto is interpreted as a storage qualifier and the type is defaulted to int. There's probably some switch for dmc to enable C++11, I don't use it myself though.