Homework 3

22C:18, Spring 1996

Due Tuesday Feb. 6, 1996, in discussion

Notice: We are working to install MAS on all macs in 103 MLH. It is installed on many of them (under the Apple menu). PLEASE DO NOT EDIT OR DELETE FILES IN THE MAS FOLDER!

1. Use MAS to produce a printed assembly listing of the following, with added comments that give your name, the name of this class, and your section:

   	xref	stop, newline, strout
   start:
   	lea	msg,a0		; address
   	move.w  #msglen,d0	; length
   	jsr	strout		; call strout( address, count )
   	jsr	newline		; call newline
   	jsr	stop		; the end!
   
   	data
   
   msg:	dc.b	'hello world'
   msglen: equ	*-hello
   
   	end
   

2. Given that the low word of d3 holds x, a 16 bit value, write a short sequence of M68000 instructions to compute abs(x) (the absolute value).

3. What value does the following sequence of M68000 instructions leave in d5?

   	move.w	#$00FF,d5
   	ori.w	#$0F0F,d5
   	andi.w	#$3333,d5
   	eori.w	#$5555,d5
   

4. Assuming that all variables are 32 bit integers, and that the registers d1, d2 and d3 are used to hold the variablex x, y and z, write a sequence of M68000 assembly language instructions that is equivalent to the following sequence of Pascal instructions:

       x := 0;
       y := 1;
       repeat
   	z := x + y;
   	y := x;
   	x := z;
   	writeln( 'value = ', z )
       until z > 1000
   

   You need not run this program, but you may; this problem counts twice as much as the previous problems on this assignment!