Atari Character Set
The ATARI 65XE personal computer comes equipped with an Atari Character Set. You can access up to 29 of these graphic characters by keeping the Control key held down and press any of the alphabet keys, semicolon, , comma, and period keys. Try holding down the control key while sitting at your keyboard and pressing the letter T for example. A circle shape will appear on the screen.
Examine the keyboard closely underneath and you will see the character that can be produced by pressing control and that corresponding key. Turn on your computer by flipping the On/Off switch, located on the back left hand side.
You will need to wait for the computer to finish the loading, which is signaled by a audio sound. When this stops you are now ready to use your computer. Try to create a work of art and have fun!
Using your imagination you can create really fantastic works of art! In the example above, I have created a spaceship using the key combination (control A, control T, control D). The next graphic is supposed to represent the wings of a bird. Then there is a pyramid. Finally you will see characters that can help you generate an idea for a cool card game. The possibilities are endless when your mind is running the show.
This is one of the best things about learning to draw with the Atari Character Set. Much later, we may find time to create an ASCII game, but that will involve a knowledge of learning how to write program in BASIC (Beginners All Symbolic Instruction Code) language.
Redefining an Atari 65xe Character Set
There are also ways you will discover later in how to change these characters into your own designs and produce what are known as “redefined characters”. The redefined part means to alter the original image of a character set and “re-define” your own style of art.
I consider myself an artist and my favorite thing to do is changing a computer’s graphic character set to create incredible worlds that you can navigate a game character through, but we will explore that much later.
Atari Pixel Graphics
If you get very close to your monitor or television screen you will see that it is made up of tiny dots. These are known as pixels and work together in combination with the phosphors to generate light on your screen. Each graphic character is made up of 64 pixels, even where you see the blank spaces in between the graphics.
When we get into redefining a character set, you will need to grasp what this is all about. It involves understanding your computer’s memory at the lowest level (known as binary). Let’s examine a game and get to work.
Caverns of the Minotaur
So in order to redefine a character set to create your own graphics, you actually have to copy ROM memory to RAM so it can be overwritten. Then modification of the character set can now allow you to create interesting games in Basic. The example seen here is a screenshot from a game called Caverns of the Minotaur. I’ve also included screenshots of the magazine listings below. Click on them to enlarge them.
The game Caverns of the Minotaur is found in ANTIC magazine’s Feb/March 1990 issue. ANTIC was a very popular magazine company that followed the 8 bit line as far back as 1982, as I recall. I would be happy to do more reviews for ANTIC as I own nearly the entire collection from 1982-1993, including the Start magazines were they ended up dumping their last issues in.
Each issue came packed with game type in programs, assembly language tutorials, applications, tips, news for the editors, game reviews, sometimes electronic mods, and so much more. This was primarily left open to the contributors who supported it.
The character set lowers RAMTOP (memory location 106 – $6A) by 8 pages, and stores these in memory location 206 ($CE) as seen below.
3 CLR:DIM P1$(20):A=PEEK(106)-8:NCB=A*256:POKE 204, A:POKE 206, 224
Then it reads in a machine language string routine into P1$. Line 6 executes the subroutine in memory, which moves the character set from ROM to RAM to setup for our redefined character routine.
4 FOR X=1 TO 20:READ B:P1$(X, X)=CHR$(B):NEXT X
5 DATA 104,162,4,160,0,177,205,145,203,200,208,249,230,206,230,204,202,208,242,96
The next lines initialize the display list, setup some variables for the maze, lives, skill, and read in the new redefined character set data using line 40.
10 DATA 0,0,224,191,165,229,0,0,56,56,16,56,84,16,40,108,60,126,195,223,209,219,66,60,0,24,60,126,126,60,24,0
20 DATA 0,0,0,15,19,27,3,7,0,0,240,200,216,192,224,60,24,255,255,189,189,36,102
30 DATA 187,187,187,0,238,238,238,0
35 RESTORE 10
40 FOR D=NCB+1*8 TO NCB+9*8-1:READ E:POKE D,E:NEXT D