Expanded monsters on the Vic. Eric Luce; James Wheeler.
Being able to create your own customized characters, from monsters and battleships to specialized scientific symbols or foreign language alphabets, is a big advantage in personalizing your own computer programs.
There are several programs available to Commodore Vic 20 owners which allow you to create individualized characters. One is Commodore's own cassette program, the Programmable Character Set and Gamegraphics Editor. Another, called "8x8 Create," appeared on pages 270 and 272 of the January 1983 issue of Creative Computing. Both programs will give you the data statements you need to esign almost any figure from a tree to a spaceship and have direct access to it from the keyboard.
When completed, your customized villain or hero will be size of a capital letter, although the Commodore program manual suggests that you join several shapes together to form larger figures.
A problem arises, however, when you try to use the new characters in a memory-expanded Vic--they won't work.
When you add memory to the Vic, it does some location shifting, and as a result the area in which you store your special characters is used for another purpose.
Fortunately, there is a method which will allow you to use your custom figures on an expanded Vic.
First, type in the lines in Listing 1 which POKE into the buffer the memory pointers to reserve memory for special characters at the beginning of user RAM. They also provide for automatically loading and running your special character program.
Without running it, save this program at the beginning of a casette tape. Verify it and then press the stop button on the cassette player. Do not rewind the tape.
Next turn the computer off, then on and type
POKE 44,24:POKE 46,24:POKE 48,24:POKE 50,24:POKE 63,10:POKE 65,5:NEW
Hit the return key and disregard the syntax error message you get on the screen.
You are now ready to type in the data for your first special character. Begin with line number 10 (do not use any line numbers before 10). Other data statements for additional custom figures can be on lines 11 through 19 or any other number after 10 except those used in Listing 2.
Your last data statement must end with-99 to tell the computer where the character data ends. For example 19 DATA 0,20,28,28,28,8, 62,8,20,34,-99
Now type in Listing 2, omitting the REM statements, if necessary, to conserve memory.
Continue by adding your own program to this one, using 220 as your first line number. To run your program when you finish it, type the command RUN 20 (just RUN will result in a syntax error). Save your completed program on tape immediately following the saved first program (Listing 1) and verify it. Your cursor will look different, but don't worry. It will work fine.
The next time you want to load your program from tape, turn the computer off, then on. Rewind the tape to the beginning, and press the stop button. Hold down the Vic shift key, hit and release the run/stop key, and release the shift key. The program will run automatically. To run it a second time, type RUN 20.
If you forget to use this method and type LOAD instead, the program will load only partially. In this case just type RUN, which will complete the loading process.
We have included the Minotaur program from More Basic Computer Games (Creative Computing Press, 1979) to provide a sample of the designs you can use. This game, which we have edited and adapted for the Vic, uses special characters for the villain (the Minotaur), the hero (you), a hunting net, stars, and an unidentified fellow with a hunting horn. To type it in, first type in the program in Listing 1 and save it as directed previously. Turn the computer off, then on, and type POKE 44,24:POKE 46,24:POKE 48, 24:POKE 50,24:POKE 63,10: POKE 65,5:NEW
Hit the RETURN key (disregarding the error message), and add the Minotaur program as listed. Save it, verify it, and load it according to the directions in the preceding paragraphs. It requires an 8K expander.