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From: shawn@marilyn.UUCP (Shawn P. Stanley)
Newsgroups: comp.sys.apple
Subject: Re: Reading the 80 column screen
Message-ID: <11@marilyn.UUCP>
Date: 8 Nov 89 13:25:04 GMT
References: <1989Nov3.044252.8555@polyslo.CalPoly.EDU>
Reply-To: shawn@marilyn.UUCP (Shawn P. Stanley)
Organization: Litfal
Lines: 25

In article <1989Nov3.044252.8555@polyslo.CalPoly.EDU> jearls@polyslo.CalPoly.EDU writes:
>Does anyone have any (8-bit) source for reading a specific character off
>of the 80-column screen?  Assembly or C or Pascal will do, just so I get
>an idea of what is needed...

Use a routine called BASCALC at $FBC1 to get the line address into $28-$29.
Do this by loading the line number into the A-register before calling $FBC1.
If the horizontal position is odd (I believe; maybe it's even), add 4 to
location $29.  Then, divide the horizontal position by two and load with
Y-register indirectly through $28-$29:

SPEEK   phy
        ldy CV
        jsr BASCALC
        lda CH
        lsr A
        tay
        bcc S1
        clc
        lda #4
        adc $29
        sta $29
S1      lda ($28),y
        ply
        rts