atof

  #include <cstdlib>
  double atof( const char *str );

The function atof() converts str into a double, then returns that value. str must start with a valid number, but can be terminated with any non-numerical character, other than "E" or "e". For example,

   x = atof( "42.0is_the_answer" );           

results in x being set to 42.0.