Hello there, everybody, from a newbie. I have shaved my head and put
on my Shoalin robes. I have a few questions, and one comment to make.
(I know these may seem trivial to those of you who know what you're
doing, but I gotta start somewhere.) Please red pencil where I am
wrong.
1) I was looking over some of the disassembled code printouts and I
notice that there are no "memory locations" (roughly analogous to line
numbers in BASIC?) listed by the code. So how is the code put in?
Where to the memory location assignments come in? And if you just
start typing everything in, how do you know where the JSR and JMP
commands are supposed to lead to?
2) I was reading a book on programming the Apple IIe (6502 processor,
doncha know), and it mentions that the branch commands only go 127 (or
128, depending on direction) bytes at the most. Has anybody ever run
into a situation where branches are required further than this?
3) Please explain the Stack Pointer with regards to the subroutines.
What location in memory is it? How big is it?
4) Supposing I JSR to a JMP command. Will a RTS send the program
back to the command after JSR, or will I screw up the program?
5) When the Atari powers up, are all the memory locations, flags,
etc. reset automatically, or in some random state so the programmer
needs to reset them himself?
6) Is there a way to produce text for a few words on the Atari, or do
any words have to be drawn out by the graphics engine (is that the
right term?)?
7) What exactly is the deal with bankswitching? If I recall what I
read correctly, the Atari has 4K of memory. The standard cart is 4K.
For 6K, presumably, one 2K bank would be retained in memory while the
other 2K bank is swapped with another. Okay. Assuming I'm
remembering correctly, how does the bankswitching command know which
bank to keep, which to replace, and what to replace it with? Am I
missing any important info here?
Finally, regarding Glen's posting about a ROM image for River Raid and
other advances, my immediate response is, "Why bother?" I have
fantasies about programming a quest game for the Atari, but I know
full well that if I can't make it fit in a cartridge without the
trimmings that modifying the emulator provides, it kind of defeats the
purpose and I can get closer to my goal learning to program on my
Windows machine (besides, graphics aren't everything. Anybody play
"Catfight"?). The Atari is like any artistic medium, such as glass
etching or pen-and-ink. They are both drawing, but each medium by its
execution automatically affects anything done with it, and sometimes,
one is simply not suited to the other. Presumably, the introductory
level of "Myst" can be done on the Atari, consisting mainly of still
images (if you have the memory, of course). But why bother? The game
is better suited to graphics engines that can display the curiosity
and wonder of the images. Even if the Atari had 1 gigabyte, it
wouldn't work, if you will. So I move that we leave the Atari and its
limitations alone, and deal with them.
Whew! Sorry if I've gone over already trod ground, and sorry if I ask
so many questions. But any help will be appreciated. (P.S. I will no
doubt have more questions as I learn, so this is your only chance to
not encourage me.)
Sincerely,
Pete Holland Jr.
_________________________________________________________
DO YOU YAHOO!?
Get your free @yahoo.com address at http://mail.yahoo.com
--
Archives (includes files) at http://www.biglist.com/lists/stella/archives/
Unsub & more at http://www.biglist.com/lists/stella/
