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Chapter 5
The screen editor
When you use BASIC or almost any application program, you will
interact with the HX-20 by typing on the keyboard, and it will
respond by displaying text and graphics on the screen. This is made
possible by the screen editor. Because the screen editor is central to
almost all HX-20 applications, you can do little with the HX-20
until you learn how to use it.
Since the screen editor is so important, this chapter will show you
how to use it in a “hands-on” fashion.
The
virtual
screen
The LCD screen can display four lines of text, with twenty
characters per line. That won’t let you display a lot of information.
That’s where the screen editor comes in. By using the screen
editor, the HX-20 can display information on a very large virtual
screen. The virtual screen doesn’t have a physical existence, like the
LCD screen, but is rather an imaginary screen. You can think of it as
lying just behind the LCD screen.
The dimensions of the virtual screen can vary according to the
program you run, but in most cases the virtual screen will be eight
lines high and forty characters wide-twice as high and twice as
wide as the LCD screen itself. The LCD screen is merely a window
onto this virtual screen. By pressing appropriate keys, you may
move this window up, down, left, and right, thus bringing into view
any desired portion of the virtual screen.
This means that you won’t be limited by the size of the LCD
screen, but can interact with the HX-20 as if it had a much bigger
display.
How can a small window allow you to view the text on a large
virtual screen? To understand how this works, tear page 37 out of
this book, and use scissors to cut out the white box on that page.
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