[comp.sys.apple] a diagnostic for the weird characters

sdh@thumper.UUCP (01/26/87)

You may want to try the following simple program in both 80
and 40 column modes to help you track down the source of your
problems.

300:	LDA $C000   ; read keyboard strobe
303:	BPL $0300   ; branc back until high bit set (key pressed)
305:	BIT $C010   ; clear strobe
308:	JSR $FDDA   ; print ascii of value read in HEX
30B:	JSR $FD8E   ; print a carriage return
30E:	JMP $0300   ; loop infinite.

That may help you out to find out exactly what is being read in both cases.
As an alternative, it could be buffered up so you can read the output in
80 column mode after testing in 40.

If you want code for that, let me know, and I can whip something up.

Steve Hawley