2 ; Ullrich von Bassewitz, 02.06.1998
11 cpx #$00 ; Outside valid range?
12 bne L9 ; If so, return the argument unchanged
14 lda __ctype,y ; Get character classification
16 lsr a ; Get bit 1 (upper case char) into carry
17 tya ; Get char back into A
18 bcc L9 ; Jump if no upper case char
19 sbc #<('A'-'a') ; Make lower case char (carry already set)