Hello World!

This document contains the following exercises:

Creating a Program

You will now write your first short program which displays "Hello World!". It will be stored in the library you have created previously.

Start of instruction setTo create a new program

  1. In the library workspace, select the library named TUTORIAL.

  2. From the context menu, choose New Source > Program.

    Or:
    Choose the following toolbar button:

    Program

    The program editor appears. It is currently empty.

  3. Enter the following code in the program editor:

    * The "Hello world!" example in Natural.
*
DISPLAY "Hello world!"
END /* End of program

    Comment lines start with an asterisk (*) followed by at least one blank or a second asterisk. When you forget to enter the blank or second asterisk, Natural assumes that you have specified a system variable; this will result in an error.

    If you want to insert empty lines in your program, you should define them as comment lines. This is helpful, if you want to access your program from different platforms (Windows, mainframe, UNIX or OpenVMS). With the mainframe version of Natural, for example, the default is that empty lines are automatically deleted when you press ENTER.

    You can also insert comments at the end of a statement line. In this case, the comment starts with a slash followed by an asterisk (/*).

    The text that is to be shown in the output is defined with the DISPLAY statement. It is enclosed in quotation marks.

    The END statement is used to mark the physical end of a Natural program. Each program must end with END.

Running a Program

The system command RUN automatically invokes the system command CHECK which checks the program code for errors. If no error is found, the program is compiled on the fly and then executed.

Notes:

  1. The system commands are also available with the mainframe version of Natural. Under Windows, they are invoked by choosing the corresponding command from the Object menu.
  2. CHECK is also available as a separate command in the Object menu.
  3. Natural also provides the system command EXECUTE which uses the stowed version of your program (stowing a program is explained later in this tutorial). In contrast to this, the RUN command always uses your latest modifications to the program.

Start of instruction setTo run a program

  1. From the Object menu, choose Run.

    Or:
    Choose the following toolbar button:

    Run

    When your code is syntactically correct, the output contains the text you have defined. 

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Hello world!

  2. Press ENTER to return to the program editor.

Correcting Program Errors

You will now create an error in your Hello World program and then run the program once more.

Start of instruction setTo correct an error

  1. Delete the second quotation mark in the line containing the DISPLAY statement.

  2. Run the program once more as described above.

    When the error is found, a dialog box appears, providing information on the error.

    Error

  3. Correct the error in the dialog box, that is: insert the missing quotation mark at the end of the line.

  4. Choose the Continue button to find the next error.

    In this case, no more errors are found and the output is shown.

  5. Press ENTER to return to the program editor.

    Note:
    Instead of choosing the Continue button, it is also possible to choose the Edit button. The dialog box is then closed and you can correct the error directly in the program editor.

Stowing a Program

When you stow a program, it is compiled and both source code and a generated program are stored in the Natural system file.

Like the RUN command, the system command STOW automatically invokes the CHECK command. A program is only stowed when it is syntactically correct.

Note:
If you want to save the changes to your program, even if the program contains a syntactical error (for example, if you want to suspend your work until the next day), you can use the system command SAVE which can be invoked from the Object menu.

Start of instruction setTo stow a program

  1. From the Object menu, choose Stow.

    Or:
    Choose the following toolbar button:

    Stow

    Since your program has not yet been saved, the Stow As dialog box appears.

    Stow as

    The name of the currently selected library is automatically provided in the corresponding drop-down list box.

  2. Specify the name "HELLO" in the Name text box.

  3. Choose the OK button.

    A message is now shown, informing you that stowing was successful. This message is either shown in the status bar or in a dialog box, depending on the setting of a specific workspace option (see below).

    In the library workspace, a new node named Programs appears below the TUTORIAL node. This node contains the program you have just stowed.

    Programs node

    The green dot on the program icon indicates that both source code and a generated program are available for the object.

Setting the Workspace Options

You will now check the settings of your workspace options.

Start of instruction setTo check the workspace options

  1. From the Tools menu, choose Options.

  2. In the resulting Options dialog box, display the Workspace page.

    Workspace

  3. When success messages are to be shown in a dialog box, make sure that the corresponding check box is selected.

    Note:
    Whether line numbers are shown in the program editor is controlled by an option on the Program Editor page.

  4. Choose the OK button to save your changes and to close the dialog box.

You can now proceed with the next exercises: Database Access.