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Programming in User RPL - Displaying output
In this last page of the tutorial, you'll learn how to display the output of your programs in a nice way. Because
if your program has a nice way to enter the input, like the ones which you saw on
last page, it should also have a nice way to display
the output.
The command MSGBOX takes only one argument: a string. It displays that string in a nice message
box. The message box has at least two line, so if your text is very short, there will be a blank line. You may enter
line breaks, if you don't, the text will be wrapped automatically.
To make the HP produce a sound, use the BEEP command. If the beep has been deactivated, then the
beep will not be produced. The command takes two arguments: on level two, the frequency of the sound, in Hz. On level
one, the duration. Then, it beeps.
DISP is the command used to display strings on the screen. It takes a string (or any other object,
which will be converted to a string) and the line number (from one to seven) from the stack, and displays. You may
include line breaks in the string, this way you may display more than one line each time. Only ths line(s) where the
text will be displayed are cleared.
If you tried DISP (if you haven't, try it now), you noticed that the text only remains in the display
for a very short time. To help this, we have FREEZE. It takes one parameter: the are to freeze. That area(s)
are not updated until a key is pressed. The numbers are as follows:
| 1 | Status area |
| 2 | Stack |
| 3 | Status and stack |
| 4 | Menu |
| 5 | Menu and status area |
| 6 | Menu and stack |
| 0 or 7 | Whole display |
Clearing the Display
And the last command of this subject and of this tutorial is CLLCD. OK, I should have finished with
a big command, with many arguments, etc., but CLLCD is very simple. It takes no arguments, returns no
results, and clears the whole screen. The stack, or PICT aren't actually cleared, only the display. It
is normally used before DISP.
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