1. Move the cursor into this viewer and press the Enter key on the keypad. This will cause the viewer to be marked (a star will appear).
2. Execute the command Compiler.Compile * (press control key over it). A star as a parameter means to use the contents of the marked viewer.
3. You may now invoke the new command Demo.Do as often as you like. Just move the mouse cursor over it and press control.
4. Modify the program, for example by changing the text that is printed.
5. Compile again by invoking Compiler.Compile * as usual.
6. Execute Demo.Do again: the changes you made in the program have no effect (yet), because the old version of module Demo is still loaded.
7. You may (re-)load the latest version of a command by interclicking the mouse button during invocation (pressing the control key).
8. Error positions in the text may be located by selecting the error message "pos ... err ..." in the System.Log and executing Edit.Locate . Selecting the first character on the line is sufficient.