Re: Seeking reverse-engineers - Apple II VisiCalc

[Toinet <antoine.vignau@laposte.net>]

Hi All,
I played with the version on asimov whose reference has given by Eric
and here is my conclusion: what do you really want to get?

The boot process is the following:
1- VC/80 1 is loaded at $0804..$08FF and then executed.
2- that code then loads the hidden part of VC/80 1 from $0900..$34FF
3- jump to $1800
4- do you want a 80-column display?
4a- if yes, do you have a videx?
5- move $1600..$16FF to $0000..$00FF
6- move $1700..$17FF to $0300..$03FF

Then, second step:
1- BRUN VC/80 2 from $0804..$08FF
2- that code then loads the hidden part of VC/80 2 from $3200..$9FFF
3- jump to $18B7
4- copy 8 bytes table from $1A00..$1A3F to the screen holes in
$0400..$07FF
5- jump to $0936 for a 80-col display or $09F1 for a 40-col display

Third step:
1- copy $0A0E..$0B0D to $0060..$015F
2- jump to $0060
2a- copy $3200..$33FF to $0200..$03FF (but keep $03E0..$03FF values)
2b- copy $3800..$9FFF to $0800..$6FFF
2c- jump to ($0028)

The code at $0060 sets the final jump address depending on the display
mode and the videx card: the standard 40-col display mode sets those
to $37 and $5A therefore the entry point is $5A37. Gotcha ;-)

If you want the create the source code of the program then make it
from the following RAM addresses:
- $0000..$00FF
- $0200..$03FF
- $0800..$6FFF
If you are patient, create the source code of the included DOS:
- $A000..$BFFF

Good luck,

Antoine Vignau
Brutal Deluxe Software