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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