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PROGRAM dynamic;
 
{ DYNAMIC.PAS illustrates the use of dynamic variables with the
  following procedures:
 
      Dispose    New
 
  It also uses two procedures to generate random numbers:
 
      Random     Randomize
}
 
USES
    Crt;
 
CONST
    program_name = 'DYNAMIC ';
    program_desc = 'builds a simple linked list of records.';
 
TYPE
    record_ptr_t = ^record_t;
    record_t = RECORD
        name     : STRING[40];
        id       : Integer;
        amount   : Real;
        next_rec : record_ptr_t;
        END;
 
VAR
    record_ptr   : record_ptr_t;
    first_record : record_ptr_t;
    answer       : Char;
 
BEGIN
 
    Writeln( program_name, program_desc );
    Writeln;
    Writeln( program_name,
             'will prompt you for a string for each record,' );
    Writeln( 'and will randomly generate two additional fields.' );
    Write( 'Type a string up to 40 characters long in response to ' );
    Writeln( 'the Name: prompt.' );
 
    Randomize;
 
    { Build simple linked list. }
    first_record := NIL;
 
    REPEAT
        New( record_ptr );
        WITH record_ptr^ DO
            BEGIN
            Write( 'Name: ' );
            Readln( name );
            id := Random( 255 );
            amount := Random * 10;
            Writeln( 'Random id:', id:4, ' Random real: ', amount:3:2 );
            next_rec := first_record;
            END;
        first_record := record_ptr;
        REPEAT
            Write( 'More? (''Y'' or ENTER to continue; ''N'' to quit)' );
            answer := ReadKey;
            Writeln( answer );
            answer := UpCase( answer );
        UNTIL (answer = 'Y') OR (answer = 'N') OR (answer = Chr( 13 ));
    UNTIL (answer = 'N');
 
    { Traverse the list, print its contents, and release pointers. }
    WHILE (record_ptr <> NIL) DO
        BEGIN
        Writeln;
        WITH record_ptr^ DO
            BEGIN
            Writeln( name );
            Writeln( id:4 );
            Writeln( amount:3:2 );
            END; { WITH statement }
        Dispose( record_ptr );
        record_ptr := record_ptr^.next_rec;
        END;
 
END.