Re: Changing the ASCII character

[Cameron Kaiser <cdkaiser@delete.these.four.words.concentric.net>]

Rubywand <rubywand@swbell.net> writes:

>> Hey, a thought:  During my Commodore programming days, all one had to
>> do to make a custom character was to POKE values for each horizontal
>> line of the character (8x8 grid).  I did whole character sets with
>> FOR X=0 TO 7 : READ A : POKE xxxxx+X : NEXT : DATA xx,xx,xx,xx, (etc)
>> -- so is there something similar available to the Apple?
>
>     The C-64 is different from the Apple II.

Yep! ;-)

>     The Apple II's Text display characters are in ROM (or PROM or
>somewhere else other than RAM).  When a Text screen is displayed the
>ASCII values from RAM are translated on-the-fly to dot patterns via the
>character generator ROM/PROM.
>     If you want to change one or more Text display characters, you need
>to swap in a custom PROM (or tack on a PROM and supply decoding, which
>is more bother than just doing a new PROM).

What he meant to say is that on the 64, you can *copy* the character set out
of Char ROM, put it in RAM, tweak it, and then tell the VIC2 video chip to use
that set instead. I've never seen this done on the Apple II, so I assume
it's not possible, but I'm curious too. Is this behaviour hardwired into
whatever logic array powers the display?

--
------------------ C64 software lives: http://computerworkshops.home.ml.org/ --
Cameron Kaiser                     | "A free society is one where it is safe
cdkaiser@concentricKILLSPAMnet     |  to be unpopular." -- Adlai Stevenson
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