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2022-08-26
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QUESTIONS AND ANSWERS
From: Carswell 31024
Peeks and Pokes Part 22 and 23 on
Issue #10 of LOADSTAR outlines how to
use a basic program to scroll left.
Every time I tried to use this program
with mine, the program crashes. I have
been unable to figure out why. Any
suggestions? I was successful in using
the M/L program as you described and
it worked fine as long as I loaded
"SCROLL.L/R" from your disk. When
saving "SCROLL.L/R" to my disk, it
would not work. What instructions do
I need to save "SCROLL.L/R" to my
disk?
>SCROLL.L/R is a machine-language
routine. It is not as easy to save
a ML file as it is to save a BASIC
program. But, to help in the
process, here is a small BASIC
routine which should do the job. To
use this routine, you need to know
the starting and ending addresses (or
a close approximation--it is better
to guess too big than too small).
First LOAD the ML file you want to
save onto another disk. Do this with
the common LOAD"name",8,1. After
this, type NEW. Then LOAD and RUN
this program with just the ',8'
format. Then remove your disk and
insert the disk you want the ML
routine saved on to (make sure it is
formatted). The program will ask
you what to call your new ML file.
You may call it anything you want.
Here is the actual program. Make
sure you type it in correctly.
10 INPUT"What file name ";N$
20 N$=N$+",p"
30 INPUT"Starting address";SA
40 INPUT"Ending address ";EA
45 OPEN2,8,2,N$
50 POKE254,INT(SA/256)
60 POKE253,SA-256*PEEK(254)
70 POKE780,253
80 POKE782,INT(EA/256)
90 POKE781,EA-256*PEEK(782)
100 SYS 65496:CLOSE2
110 PRINT"FINISHED!!"
120 END
By the way, the starting address of
SCROLL.L/R is 49152. The ending
address is approximatly 49664.
- - - - - - - - - - - - - - - - - - -
From: Carswell 31024
Your up and down bounce at the end
of each feature is fascinating. Do
you care to tell how it's done?
>Well, the secret is behind what is
called the raster. Without getting
into the messy details, let's say
that the raster is the technical term
for your video output. Now, here is
how you do our little 'bounce'.
10 W=53265:U=128
20 FOR I = 27 to 31:WAIT W,U:POKE W,I:
NEXT I
30 FOR I = 31 to 27 STEP -1:WAIT W,U:
POKE W,U:NEXT I
---------< end of article >-----------