-- Simple Ada program which doubles a given integer

    WITH text_io ; USE text_io ; -- Maks standard text I/O available

    PROCEDURE double IS -- program specification

-- Generic Package Instantiations :

    PACKAGE int_io IS NEW integer_io ( integer ) ; USE int_io ;

-- Global Variables :

    value  : INTEGER ; -- value to be doubled
    double : INTEGER ; -- result

    BEGIN -- double

    PUT ( "Value to be doubled ? " ) ; -- prompt user
    GET ( value ) ;                    -- read number
    double := value * 2 ;              -- multiply by two
    PUT ( value ) ;                    -- print value given by user
    PUT ( " * 2 = " ) ;                -- print explanatory string
    PUT ( double ) ;                   -- print result
    NEW_LINE ;                         -- move on to next output line

    EXCEPTION -- exception handler to trap data and numerical errors

       WHEN numeric_error => -- trap integer overflow

          PUT ( "! Error - Numerical error exception raised." ) ;
          NEW_LINE ;

       WHEN data_error => -- trap non-integer input

          SKIP_LINE ; -- skip over rest of input line
          PUT ( "! Error - Data error exception raised." ) ;
          NEW_LINE ;

    END double ; -------------------------------------------------------