Chapter 9 - Example programs


             The  programs included in this chapter are intended  to
        be  illustrations to you in how to write a complete program.
        The  programs  are meant to be useful to you  either  as  an
        example  of how to do some operation or as utility  programs
        for your general use.

                        TIMEDATE - Get Time and Date

             This  program calls one of the DOS functions to get the
        current time and date.   They are input as variables and can
        be  printed  or displayed in any format  you  desire.   Your
        particular compiler may use a different format because there
        is no standard in Modula-2.  This is one of those areas that
        will  probably deviate from compiler to  compiler.   If  you
        study  your documentation that came with your compiler,  you
        will  find many other calls of this  type  described.   This
        program  is  meant to be an illustration of how to use  this
        particular call.

                          AREAS - Calculate Areas

             This program is intended to be an illustration for  you
        of  how to build up a larger program than any other that  we
        have  examined  up  to this point.   Notice  that  the  main
        program  is simply one CASE statement that calls all of  the
        other  procedures.   It would be very simple to include  the
        code  from  each procedure right in the CASE  statement  and
        have no procedure calls,  but it would make the program very
        difficult to understand.  The way this example is coded, the
        code  is very easy to understand.   After you understand the
        main  program,  it  is a very simple matter  to  visit  each
        procedure to see exactly what they do.

             Notice  how the menu works in this program.   It  reads
        one  keystroke  and  responds immediately making it  a  very
        simple program to use.

                            PC - Printer Control

             This  is  a  very useful program that you  can  use  to
        control  your  printer.   It is specifically set up  for  an
        Epson  RX-80,  but you can modify the control characters  to
        set up your printer to whatever mode you desire.  To use the
        program,  you  call the program and supply a  single  letter
        according  to the displayed menu,  and the program will send
        the  character  or characters to the printer to  select  the
        enhanced,  compressed, or whatever mode you desire.  If your
        printer is located physically remote from you,  you can  use
        this  program to send a formfeed to the printer by selecting
        the F option.   If you have some longer control sequences to
        send, you may want to store the values in a string and use a


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                        Chapter 9 - Example programs


        loop to output the data until you come to an 0C character.

                          LIST - List Program File

             If you ran the batch file named LISTALL as suggested at
        the  beginning  of  this tutorial to print out  all  of  the
        source files, you have already used this program.  It is the
        program that will list any ASCII file,  adding line numbers,
        page numbers,  and the date and time, on the printer.  It is
        specifically designed to be a program listing utility.   The
        operation is very simple,  and you should have no trouble in
        understanding this program or what it does.

             Additional  programs  will be given at the end of  Part
        III for your information.  You will no doubt find additional
        example  programs  in various books and periodicals  and  it
        would  be to your advantage to to spend some  time  studying
        them as illustrations of both good and bad practices.



































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