let getch' n = 
       try
         match n with
           | 260 -> "left"
           | 261 -> "right"
           | 259 -> "up"
           | 258 -> "down"
           | 10 | 343 -> "enter"
           | 331 -> "0"
           | 360 -> "1"
           | 338 -> "3"
           | 339 -> "9"
           | 262 -> "7"
           | n -> string_of_char (char_of_int n)
       with _ -> "unknown"