     $AC-$AD/172-173:   Pointer: Tape Buffer/Screen scrolling

    Kernal-Reference:

     CMP ($AC),Y : $FAE3 $FB28
     INC $AC     : $FCDB
     LDA $AC     : $E8EA $E981 $E9E3 $F61A $FAFC $FB0E $FCD2
         ($AC),Y : $E9D4 $F629 $FB72 $FC41
     STA $AC     : $E90A $E962 $E99D $FB94
         ($AC),Y : $FB41

     INC $AD     : $FC37 $FCDF
     LDA $AD     : $E8ED $E984 $E9E7 $F61F $FAF7 $FB15 $FCD6
     STA $AD     : $E95F $E9CD $FB90