CSC231 Homework 4 Solutions 2014

--D. Thiebaut (talk) 16:16, 21 October 2014 (EDT)

---

Problem #1

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;;; ; -------------------------------------------------------------------
;;; ; hw4a.asm
;;; ; Lei Lei
;;; ;
;;; ; Given the following definition:
;;; ; msg     	db    	3,"ALL",11,"PROGRAMMERS",3,"ARE",11,"PLAYWRIGHTS"
;;; ;         	db    	3,"AND",3,"ALL",9,"COMPUTERS",3,"ARE",5,"LOUSY"
;;; ;         	db    	6,"ACTORS"
;;; ; This program outputs each letter of msg capitalized in a line:
;;; ;
;;; ;  All
;;; ;  Programmers
;;; ;  Are
;;; ;  Playwrights
;;; ;  And
;;; ;  All
;;; ;  Computers
;;; ;  Are
;;; ;  Lousy
;;; ;  Actors
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ;     nasm -f elf -F  stabs hw4a.asm
;;; ;     ld -o hw4a hw4a.o
;;; ;     ./hw4a
;;; ; -------------------------------------------------------------------


;;; ; -----------------------------------------------------------
;;; ; Constants
;;; ; -----------------------------------------------------------
	EXIT    equ             1
	WRITE   equ             4
	STDOUT  equ             1

;;;  ------------------------------------------------------------
;;;  data areas
;;;  ------------------------------------------------------------

	section	.data

msg     	db    	3,"ALL",11,"PROGRAMMERS",3,"ARE",11,"PLAYWRIGHTS"
        	db    	3,"AND",3,"ALL",9,"COMPUTERS",3,"ARE",5,"LOUSY"
        	db    	6,"ACTORS"
	
N       	equ   	10

newLine		db	0x0A
line_len	equ	1
	
counter		dd	0
temp1		dd	0
temp2		dd	0
	
;;;  ------------------------------------------------------------
;;;  code area
;;;  ------------------------------------------------------------
	section .text
	global	_start
	
_start:	mov	ecx, N
	
for:	mov	dword[temp1], ecx 	;Main loop, loop for N=10 times
	mov	esi, msg
 	add 	esi, dword[counter] 	;esi points to integer
	inc	dword[counter]

	mov	eax, WRITE
	mov	ebx, STDOUT
	mov	ecx, msg	
	add	ecx, dword[counter] 	;ecx points to first letter
	mov	edx, 1
 	int	0x80			;print first letter in cap
	
	movzx	ecx, byte[byte esi] 	;move the integer to ecx
	dec	ecx			;minus the already printed first letter
	inc	dword[counter]

    	call	printLower
 	call	printLine

 	mov	ecx, dword[temp1]
 	loop	for
	
;;;  exit()

	mov	eax,EXIT
	mov	ebx,0
	int	0x80			; final system call

;;; ----------------------------------------------------------------
;;; printLower: Print letters in lower case
;;; ----------------------------------------------------------------
printLower:
forLower:	
	mov	dword[temp2], ecx
	mov	eax, WRITE
	mov	ebx, STDOUT

	mov	ecx, msg
	add	ecx, dword[counter]
	add	dword[ecx], 'a'-'A'		;change into lower case
	mov	edx, 1			
	int 	0x80		

	inc	dword[counter]		
	mov	ecx, dword[temp2]	
	loop	forLower
	ret
	
;;; ---------------------------------------------------------------
;;; printLine: Hard break and print new line
;;; ---------------------------------------------------------------
printLine:
	section	.bss
.temp	resd	1

	section .text
	mov	eax, WRITE
	mov	ebx, STDOUT
	mov	edx, line_len
	mov	dword[.temp], ecx
	lea	ecx, [newLine]
	int	0x80
	mov	ecx, dword[.temp]
	ret