; Convert a string to lowercase 
; s ->
.label lowcase
  ; store index
  POPxw
  .label lowcase.loop
    LDBxw $00 EQU lowcase.end JCNw
    ; check if an uppercase letter
    LDBxw $40 GTH
    LDBxw $5B LTH
    AND lowcase.change JCNw
    ; continue
    INCxw lowcase.loop JMPw
    .label lowcase.change
      ; convert to lowercase  
      LDBxw $20 ADD STBxw
      ; continue 
      INCxw lowcase.loop JMPw
    .label lowcase.end
      RTS