One problem with using television screens for displaying graphics is that when the set is turned off, it's bye-bye graphics. What we need is some way to print or “dump” the screen image on paper. Regular printers won't do it because they only handle alphanumeric characters. The solution is provided by Axiom Corporation in Glendale, California, which makes a special printer/plotter that works with the PET, TRS-80, and Apple computers. Called the EX-820 Microplotter, the unit prints out high-resolution graphics plus full ASCII alphanumerics. Shown in Fig. 2-32, it uses special 5-inch (12.7-cm) wide aluminized electrosensitive paper that burns off the top layer of aluminum, which covers an underlying black surface. This results in extremely high contrast characters, unlike anything obtainable on regular paper.

The EX-820 contains its own 8048 microprocessor and firmware for extensive software control. The user can select, via control sequences, three different column widths (20, 40, or 80 characters per column) and three different horizontal dot resolutions, with up to 512 dots per line. Vertical dot spacing is 65 dots per inch.


Fig. 2-32. EX-820 Microplotter can handle full alphanumerics and high-resolution graphics to 512 dots per line.


Fig. 2-33. Example of EX-820 output.


Fig. 2-34. Example of screen dump of Muppets created with digitizing table.

Several program listings used in this book were produced on the EX-820. Fig. 2-33 shows a dump of an image plotted on the screen of an Apple II computer. The screen dump was accomplished by simply typing a control R at the keyboard. The total dump took less than 6 seconds.

The EX-820 makes a nice output device for the digitizing table described earlier. Fig. 2-34 shows the image of a drawing made by David Fox at the Marin Computer Center of the popular and lovable Muppets. The digitizing table allowed the image to be perfected on the screen before it was output to the Microplotter.

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