.globl	_toupper
_toupper:
	jsr	popax		; get the char
	cmp	#'a		; < 'a'?
	bcc	toupper9	; yup, skip it
	cmp	#'z+1		; > 'z ?
	bcs	toupper9
	sec
	sbc	#$20
toupper9:
	rts