CSC231 Homework Solutions 2017

--D. Thiebaut (talk) 17:57, 22 April 2017 (EDT)

---

Problem 1

;;; mystery.asm 
;;; D. Thiebaut  
;;;                
;;; To assemble, link, and run:  
;;;     nasm -f elf  mystery.asm  
;;;     ld -melf_i386 -o mystery mystery.o 
;;;     ./mystery        
;;;      

                section .data
Hello           db      "Hello there!", 10, 10
HelloLen        equ     $-Hello
	
                section .text
                global  _start
_start:

;;; print Hello and a space after it
	
                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, Hello      ; address of message to print    
                mov     edx, 6          ; print only 6 chars
                int     0x80

;;; print ! and two line feed chars

                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, Hello+11   ; address of ! char
                mov     edx, 3          ; print only 3 chars
                int     0x80

;;; exit                                                                                                                                    
                mov     ebx, 0
                mov     eax, 1
                int     0x80

hw1.asm

;;; hw1.asm
;;; D. Thiebaut  
;;;                
;;; To assemble, link, and run:  
;;;     nasm -f elf  hw1.asm  
;;;     ld -melf_i386 -o hw1 hw1.o 
;;;     ./hw1        
;;;      

                section .data
msg             db      "  CSC231 Assembly "
linefeed	db	10
dashline        db	"------------------"
lineLen		equ	$-dashline
	
                section .text
                global  _start
_start:

;;; print message                                                                                                                           
                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, dashline   ; address of message to print    
                mov     edx, lineLen   	; # of chars to print  
                int     0x80

                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, dashline   ; address of message to print    
                mov     edx, lineLen   	; # of chars to print  
                int     0x80

		mov	eax, 4		;print line-feed
		mov	ebx, 1
		mov	ecx, linefeed
		mov	edx, 1
		int	0x80

                mov     eax, 4		; write ----
		mov     ebx, 1 		; stdout
		mov     ecx, dashline 	; address of message to print
		mov     edx, 9  	; # of chars to print
		int     0x80

                mov     eax, 4          ; write message
                mov     ebx, 1          ; stdout  
                mov     ecx, msg 	; address of message to print    
                mov     edx, lineLen    ; # of chars to print  
                int     0x80
	
                mov     eax, 4		; write ----
		mov     ebx, 1 		; stdout
		mov     ecx, dashline 	; address of message to print
		mov     edx, 9  	; # of chars to print
		int     0x80

		mov	eax, 4		;print line-feed
		mov	ebx, 1
		mov	ecx, linefeed
		mov	edx, 1
		int	0x80

                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, dashline   ; address of message to print    
                mov     edx, lineLen   	; # of chars to print  
                int     0x80

                mov     eax, 4          ; write    
                mov     ebx, 1          ; stdout  
                mov     ecx, dashline   ; address of message to print    
                mov     edx, lineLen   	; # of chars to print  
                int     0x80

		mov	eax, 4		;print line-feed
		mov	ebx, 1
		mov	ecx, linefeed
		mov	edx, 1
		int	0x80

;;; exit                                                                                                                                    
                mov     ebx, 0
                mov     eax, 1
                int     0x80

hw2.asm

;;; ; ; hw2sol.asm
;;; ; ; D. Thiebaut
;;; ; ;
;;; ; ;


	        extern  _printDec
	        extern  _printString
	        extern  _println
	        extern  _getInput
	
	section	.data
prompt		db	"> "
promptLen	equ	$-prompt	
ansStr          db      "ans = "
ansStrLen	equ	$-ansStr	

a		dd	0
b		dd	0
c		dd	0
ans		dd	0
	
		section	.text
		global	_start
_start:
	;; display prompt
		mov	ecx, prompt
		mov	edx, promptLen
		call	_printString
	;; get a
		call	_getInput
		mov	dword[a], eax

	;; display prompt
		mov	ecx, prompt
		mov	edx, promptLen
		call	_printString
	;; get b
		call	_getInput
		mov	dword[b], eax
	
	;; display prompt
		mov	ecx, prompt
		mov	edx, promptLen
		call	_printString
	;; get c
		call	_getInput
		mov	dword[c], eax
	
	;; -----------------------------------
	;; computation: ans = 2*(a-b) + 3*c
	;; -----------------------------------
	
	; your code will go here...
	

	;; -----------------------------------
	;; display "ans ="
	;; -----------------------------------
		mov	ecx, ansStr
		mov	edx, ansStrLen
		call	_printString

	;; -----------------------------------
	;; display ans variable
	;; -----------------------------------
		mov	eax, dword[ans]
		call	_printDec
		call	_println
		call	_println
	
;;; exit
		mov	ebx, 0
		mov	eax, 1
		int     0x80

Teller.asm

;;; ; teller.asm
;;; ; D. Thiebaut
;;; ;
;;; ; Demo of a teller machine program.
;;; ; To assemble, link, and run:
;;; ;     nasm -f elf  teller.asm
;;; ;     ld -melf_i386 -o teller teller.o 231Lib.o
;;; ;     ./teller
;;; ;                

;;;  extern functions that will be linked to this program
;;; ; contained in 231Lib.asm

extern  _printDec
extern  _printString
extern  _println
extern  _getInput

;;; ------------------------------------------------------
;;; DATA SECTION
;;; ------------------------------------------------------        
                section .data
amount          dd      139
no20s           dd      0
no10s           dd      0
no5s            dd      0
no1s            dd      0

msg             db      "amount? "
MSGLEN          equ     $-msg        

;;; ------------------------------------------------------
;;; CODE SECTION
;;; ------------------------------------------------------        
                section .text
                global  _start
        
_start: 

;;; get amount from the user
                mov     ecx, msg
                mov     edx, MSGLEN
                call    _printString
                call    _getInput
                mov     dword[amount], eax
        	call	_println
	
;;; Break down amount in 20s, 10s, 5s, and 1s
                mov     eax, dword[amount]
                mov     edx, 0

                mov     ebx, 20
                mov     eax, dword[amount]
                call    break
                mov     dword[no20s], eax

                mov     ebx, 10
                mov     eax, dword[amount]
                call    break
                mov     dword[no10s], eax
        
                mov     ebx, 5
                mov     eax, dword[amount]
                call    break
                mov     dword[no5s], eax
                mov     eax, dword[amount]
                mov     dword[no1s], eax

                mov     eax, dword[no20s]
                call    _printDec
                call    _println
                mov     eax, dword[no10s]
                call    _printDec
                call    _println
                mov     eax, dword[no5s]
                call    _printDec
                call    _println
                mov     eax, dword[no1s]
                call    _printDec
                call    _println
        

;;; exit
                mov     ebx, 0
                mov     eax, 1
                int     0x80

;;; sum: gets 2 ints in eax and ebx and returns the sum in
;;; eax.
sum:            add     eax, ebx,
                ret

;;; break: gets amount in eax, divider in ebx, divides,
;;; and puts remainder in [amount] and quotient in eax
break:          mov     edx, 0
                div     ebx
                mov     dword[amount], edx
                ret

hw5_1.asm

;;; ; hw5_1.asm
;;; ; D. Thiebaut
;;; ;
;;; ; Prints 10 lines of Pascal triangle.
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ;     nasm -f elf -F  stabs hw5_1.asm
;;; ;     ld -melf_i386 -o hw5_1 hw5_1.o
;;; ;     ./hw5_1
;;; ; -------------------------------------------------------------------

extern		_printString
extern		_getInput
extern		_println
	
;;;  ------------------------------------------------------------
;;;  data areas
;;;  ------------------------------------------------------------

	        section .data
prompt 		db 	"> "
stars 		db 	"******************************************"
N		dd	0
saveECX 	dd	0

;;;  ------------------------------------------------------------
;;;  code area
;;;  ------------------------------------------------------------

	        section .text
	        global  _start

_start:
;;; get N from user
		mov	ecx, prompt
		mov	edx, 2
		call	_printString
		call	_getInput
		mov	dword[N], eax
;;; -------------------------------------------------
;;; print opening triangle
		mov	ecx, dword[N]
for0:		mov	dword[saveECX], ecx

		mov	edx, dword[N]
		sub	edx, ecx
		inc	edx
		mov	ecx, stars
		call    _printString
		call	_println

		mov	ecx, dword[saveECX]
		loop	for0

;;; -------------------------------------------------
;;; print square
		mov	ecx, dword[N]
for1:		mov	dword[saveECX], ecx

;;; print a line of N stars
		mov	ecx, stars
		mov	edx, dword[N]
		call	_printString
		call	_println
	
		mov	ecx, dword[saveECX]
		loop 	for1

;;; -------------------------------------------------
;;; print closing triangle
		mov	ecx, dword[N]
for2:		mov	dword[saveECX], ecx

		mov	edx, ecx
		mov	ecx, stars
		call    _printString
		call	_println

		mov	ecx, dword[saveECX]
		loop	for2
	
;;;  exit()

	        mov     eax,1
	        mov     ebx,0
	        int     0x80	; final system call

hw5_2.sh

#! /bin/bash
# hw5_2.sh
# D. Thiebaut
# gets a number of the command line and prints a triangle
# a square and a triangle with the width equal to the value
# of the number.

N=$1

for i in $( seq 1 $N ) ; do
   for j in $( seq 1 $i ) ; do
      echo -n "*"
   done
   echo ""
done

for i in $( seq 1 $N ) ;do
    for j in $( seq 1 $N ) ; do
      echo -n "*"
   done
   echo""
done

exit

for i in $( seq 1 $N ) ;do
    top=$( expr $N - $i + 1 )
    for j in $( seq 1 $top ) ; do
      echo -n "*"
   done
   echo""
done

GameOfLife.asm

;;; ; GameOfLife.asm
;;; ; Authors: D. Thiebaut and CSC231 Class
;;; ;
;;; ; Implements a 1-dimensional version of 
;;; ; Conway's Game of life.
;;; ; Note that because we do not "know" yet
;;; ; how to test or to use functions, the code
;;; ; is not as efficient as it could be.
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ;     nasm -f elf -F  stabs GameOfLife.asm
;;; ;     ld -melf_i386 -o GameOfLife GameOfLife.o
;;; ;     ./GameOfLife
;;; ; -------------------------------------------------------------------


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

	        section .data
;;; the current dish with its cells.  We use 0 and 1 to
;;; indicate dead and live cells, respectively.
%include	"dishArray.inc"

;;; the new generation of cells.  That's the "future" of the
;;; cells in the dish.  We make it the same size as dish, and
;;; fill it with N dead cells.
	
newGen	        times   N db 0
	
;;; dishP is a string that will contain ' ' or '!' for
;;; each 0 or 1 in dish.  
dishP		times   N  db ' '
		db	10			; add a \n at the end
						;  of dishP
	
generation	dd	0			; save ecx from for generation loop
i		dd	0			; used by for loops
	
;;;  ------------------------------------------------------------
;;;  code area
;;;  ------------------------------------------------------------

	        section .text
	        global  _start

_start:
main:	
;;; -------------------------------------------------------------
;;; print( dish )
		;; first we copy dish into dishP and at the same
		;; time replace 0 by ' ' and 1 by '!'

;;; for i in range( N ):
		mov	esi, dish 
		mov	edi, dishP

		mov	dword[i], 0
forPrint:	cmp	dword[i], N
		jge	forPrintEnd
	
		mov	al, byte[esi]
		add	al, ' '			;0 becomes ' ', 1 becomes '!'
		mov	byte[edi], al
		inc	esi			;esi points to next byte in dish
		inc	edi			;edi points to next byte in dispP

		;; i++, loop back
		inc	dword[i]
		jmp	forPrint
forPrintEnd:	
	
		;; print dishP as a string.
		mov	eax, 4			;prints dishP to screen
		mov	ebx, 1
		mov	ecx, dishP 		;dishP address
		mov	edx, N+1		;+1 to include the \n
		int	0x80


;;; -----------------------------------------------------------
;;; for generation in range( maxGen ):

		mov	dword[generation], 0
	

forGen:		mov	eax, dword[generation]
		cmp	eax, dword[maxGen]
		jge	forGenEnd
	

;;; -----------------------------------------------------------
;;;      newGen = life( dish, N )
;;; 	 newGen[0] = 0
;;; 	 newGen[N-1] = 0

	        mov    byte[newGen], 0
		mov    byte[newGen+N-1], 0

;;; -----------------------------------------------------------
;;;      for i in range( 0, N ):

		mov	esi, dish
		mov	edi, newGen
	
		mov    	dword[i], 0
	
forLife:	cmp	dword[i], N
		jge  	forLifeEnd
	
;;; -----------------------------------------------------------
;;; 	     fate = dish[i-1] ^ dish[i+1]
;;; 	     newGen[i] = fate
		mov	al, byte[esi-1]
	        xor     al, byte[esi+1]
	        mov	byte[edi], al
		inc	esi
		inc	edi

		inc	dword[i]
		jmp	forLife
forLifeEnd:
	
;;; -----------------------------------------------------------
;;;     dish = newGen

		mov	dword[i],0
		mov	esi, newGen
		mov	edi, dish
		
forMove:	cmp	dword[i], N
		jge	forMoveEnd
	
		mov	al, byte[esi] 	;copy newGen[i] to dish[i]
		mov	byte[edi], al
		inc	esi
		inc	edi

		inc	dword[i]
		loop	forMove
forMoveEnd:
;;; -------------------------------------------------------------
;;; print( dish )
		;; first we copy dish into dishP and at the same
		;; time replace 0 by ' ' and 1 by '!'

;;; for i in range( N ):
		mov	esi, dish 
		mov	edi, dishP

		mov	dword[i], 0
forPrint2:	cmp	dword[i], N
		jge	forPrintEnd2
	
		mov	al, byte[esi]
		add	al, ' '			;0 becomes ' ', 1 becomes '!'
		mov	byte[edi], al
		inc	esi			;esi points to next byte in dish
		inc	edi			;edi points to next byte in dispP
		inc	dword[i]
		jmp	forPrint2
forPrintEnd2:
	
		;; print dishP as a string.
		mov	eax, 4			;prints dishP to screen
		mov	ebx, 1
		mov	ecx, dishP 		;dishP address
		mov	edx, N+1		;+1 to include the \n
		int	0x80

;;; ready to loop back to forGen
		inc	dword[generation]
		jmp	forGen
forGenEnd:
	
;;;  exit()

exit:		mov     eax,1
	        mov     ebx,0
	        int     0x80	; final system call