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Re: 40x24 Resolution Question

Bryan Parkoff wrote:
>     Yes, it is what I meant bitmaps of the characters are stored in video
> ROM that they are not stored in any memory address $0000-$FFFF.
>     I am wondering how it works.  If you want to load 'A' character before
> store it in $400, it will appear in the first column and first row.  How can
> video ROM read $400 before prints bitmaps into screen?  I am curious.

I am still having trouble understanding you.  My guess is English is
not your first language.

A long time ago when the Apple II was designed memory was faster than
the microprocessor.  The 6502 only uses the memory half the time.
Woz made the video system see the memory the other half the time.
The video system sees the 'A' at location $400, looks up the pattern
in the video ROM, and displays 'A' on the screen.

If you want more detailed information, I recommend either
"Understanding the Apple II" or "Understanding the Apple IIe", both
by Jim Sather.

Paul R. Santa-Maria
Monroe, Michigan USA