Articles by Sub-Etha Software

See also: part 1, part 2, part 3, part 4 … and more to come… Objectively speaking Welcome back to the world of Atari Adventure! After spending some time figuring out how the rooms were drawn, it’s time to look at how the game objects are drawn. Adventure contains many …

See also: part 1, part 2, part 3, part 4 and part 5 (coming “soon”). Let’s jump right in with a mystery… This code: 0 REM arrowbench.bas 10 TIMER=0:FOR A=1 TO 1000 20 POKE&H155,&HFF:POKE&H156,&HFF:POKE&H157,&HFF:POKE&H158,&HFF 30 IF PEEK(&H155)=&HF7 THEN IF Y >. THEN Y=Y-1 40 IF PEEK(&H156)=&HF7 THEN IF Y. THEN X=X-1 60 IF PEEK(&H158)=&HF7 THEN IF X.THEN Y=Y-1 40 IF PEEK(D)=V THEN IF Y.THEN X=X-1 60 IF PEEK(R)=V THEN IF X …

Recently, I was annoyed to find that there did not seem to be any way to set a black pixel on the CoCo’s normal green background. I have since been schooled in the simplest way to make this work, which I will share after a long digressing ramble. Never the …

See also: part 1, part 2, part 3, part 4. and more to come… Defining the invisible When we last left off, I was trying to figure out what all the bits did in the room definition attribute byte: ;Offset 4 : Bits 5-0 : Playfield Control ; Bit 6 …

See also: part 1, part 2, part 3, part 4 and part 5 (coming “soon”). By now, many of you have realized that I have no idea what I am doing. It’s through great comments that this series is evolving into something hopefully useful. For example, MC-10 programmer extraordinaire Jim …

The 1980 Radio Shack Color Computer (and the Color Computer 2 revisions) used a Motorola MC6847 Video Display Generator chip. This video chip was used in a variety of other systems, and one can easily recognize it by its 32×16 text mode characters with the square letter “O”. I recently …

See also: part 1, part 2, part 3, and more to come… How the rooms are defined In the previous installment, I introduced how the playfields were encoded in the Atari Adventure game. I had converted the assembly data into C code and made a command-line program that would print …

See also: part 1, part 2, part 3, part 4 and part 5 (coming “soon”). NOTE: I have a really great comment to share with you from a recent installment, but it deserves an article of it’s very own. Thank you, Jim, for the assembly sample. I’ll be getting to …

I have been on an Atari Adventure kick lately, which started after I played the game on a friend’s ATGames Legends Ultimate Arcade awhile back. Ignoring the weirdness of playing an Atari VCS game on something that resembles a 1980s arcade machine, it was like stepping back in time to …

See also: part 1, part 2, part 3, part 4 and part 5 (coming “soon”). Before I get started today, I wanted to share a comment about part 2 left by Paul Fiscarelli on the Sub-Etha Software Facebook page: Allen – one minor optimization in your assembly routine. You can …