org	$3000
START

* Test main; it's NOT part of the solution:
* macro for printing string
pstr	MACRO
	lea	\1,a1
	move.l	#13,d0
	trap	#15
	ENDM
_main:	pstr	MSG1
	pstr	MSG2
	pea	MSG1
	jsr	_yell
	pstr	MSG1		; no, so safe to print
	adda.w	#4,sp

	move.l	#9,d0		; exit
	trap	#15

*******************************************************************************
* Begin SOLUTION to midterm practice #4
*******************************************************************************
_yell:	move.l	4(sp),a0	; msg

loop	move.b	(a0),d0
	beq	exit		; exit if end of string
	cmp.b	#'a',d0
	bcs	skip		; don't modify if below 'a'
	cmp.b	#'z',d0
	bhi	skip		;   or above 'z'
	subi.b	#$20,d0		; upper to lower
	move.b	d0,(a0)		; modify in place
skip	adda.w	#1,a0
	bra	loop
	
exit	rts
*******************************************************************************
* End SOLUTION
*******************************************************************************
* Grading:
* o full credit for an essentially correct implementation with a few
*   syntax errors
* o 3/4 credit for an essentially correct main loop
*     -1/4 if forgot check for lowercase
* o 1/8 credit for an essentially correct function entry and exit
* o 1/8 credit for an essentially correct loading of the argument
* Many other correct implementations are of course possible.

MSG1	dc.b	'Hello Universe!  Here I am.',0
MSG2	dc.b	'Hello?',0

	end	START