  We present a new automatic code (ARES) for determining equivalent widths of
the absorption lines present in stellar spectra. We also describe its use for
determining fundamental spectroscopic stellar parameters.
  The code is written in C++ based on the standard method of determining EWs
and is available for the community. The code automates the manual procedure
that the users normally carry out when using interactive routines such as the
splot routine implemented in IRAF.
  We test the code using both simulated and real spectra with different levels
of resolution and noise and comparing its measurements to the manual ones
obtained in the standard way. The results shows a small systematic difference,
always below 1.5m\AA. This can be explained by errors in the manual
measurements caused by subjective continuum determination. The code works
better and faster than others tested before.
