cc65/libsrc/common/toupper.s

;
; Ullrich von Bassewitz, 02.06.1998
;
; int toupper (int c);
;

	.export		_toupper
	.import		__ctype

_toupper:
        cpx     #$00            ; Outside valid range?
        bne     L9              ; If so, return the argument unchanged
	tay			; Get c into Y
	lda	__ctype,y	; Get character classification
	lsr	a		; Get bit 0 (lower char) into carry
	tya			; Get C back into A
       	bcc    	L9		; Jump if not lower char
       	clc
       	adc    	#<('A'-'a')     ; make upper case char
L9:	rts	  		; CC are set