Posted By
Torque222
on 2018-06-18
13:59:12
 |  Graphic 1 or 2
I would like to use
0 POKE 44,128:POKE128*256,0:NEW
Now if my program says GRAPHIC 1,1
It relocates basic again right where I was trying to keep it out of.
I could do:
0 Graphic 1,1
1 Poke 44,128:Poke128*256,0:New
and then load my program (without using Graphic 1 after that)
Any better ways? Or even any other ways?
Regards,
Robert
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Posted By
SVS
on 2018-06-18
14:56:19
 | Re: Graphic 1 or 2
The BASIC has its way to easy manage the graphic. The first time you use GRAPHIC x,y the system always allocates the graphic area from $2000 to $3FFF and shift the possible BASIC lines beyond this limit (RAM cell at $75 memorizes the status: $FF allocated, $00 no).
After this operation, all the further executions of GRAPHIC x,y do not move data area nor Basic lines (Ram cell at $75 memorizes the status: $FF allocated, $00 no)
To restore the BASIC lines back to $1000 you have to use GRAPHIC CLR (then not GRAPHIC 0!)
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Posted By
Csabo
on 2018-06-18
17:19:33
| Re: Graphic 1 or 2
Just a very minor addition to what SVS said, only the topmost bit of the value on $75 is actually checked (so $80 and above = allocated, $7F and below = not allocated).
Adding POKE117,128 to your first example will work.
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Posted By
SVS
on 2018-06-20
07:43:25
| Re: Graphic 1 or 2
@Csabo: are you sure of this? Browsing the code I've only found:
DEC $75
and LDA $75: BEQ xxxx
Thank you
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Posted By
Csabo
on 2018-06-20
08:27:01
| Re: Graphic 1 or 2
Aha, you're right. $80 definitely works, that's what I always used, but to be super precise, it's 0 = unallocated, non-zero = allocated. Which means, from BASIC, it's probably best to do POKE117,1 to save 2 bytes 
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