Difference between revisions of "CSC231 Homework 4 2015"

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</bluebox>
 
</bluebox>
 
<br />
 
<br />
−
 
+
<showafterdate after="20151014 12:00" before="20151231 00:00">
 
=Preparation=
 
=Preparation=
 
<br />
 
<br />
Line 120: Line 120:
  
 
;;; ; extern functions that will be linked to this program
 
;;; ; extern functions that will be linked to this program
−
;;; ; contained in 231Lib.asm
+
;;; ; contained in 231Lib.asm and in hw4_func.asm
  
 
         extern  _printDec
 
         extern  _printDec
Line 278: Line 278:
 
<br />
 
<br />
 
<br />
 
<br />
 +
=Notes=
 +
<br />
 +
==Note 1==
 +
<br />
 +
* You are allowed to declare additional variables in your data section, if you need to.  Just add a  ''section .data'' block to your '''hw4_func.asm'''.  '''Do not modify your hw4.asm''', since you will not be submitting your hw4.asm.  A slightly different hw4.asm will be used to test your hw4_func.asm program, passing different values to your functions to make sure they work well.
 +
<br />
 +
==Note 2==
 +
<br />
 +
When Moodle compares your output to the expected output, it uses the ''diff'' Linux command, which highlights differences between the two outputs by displaying lines that mismatch with a prefix.  It uses a + sign in front of the lines from the expected output, and a - sign in front of the lines generated by the program just submitted.  Lines that are the same in both the expected output and the output of the submitted program do not have a prefix.
 +
<br />
 +
Below is an example that was generated by clicking on the '''debug''' button in Moodle, instead of '''evaluate''':
 +
<br />
 +
::<source lang="text">
 +
                                                                       
 +
average = 7                                                                   
 +
eax = 65                                                                     
 +
ebx = 37                                                                     
 +
- 3*eax - ebx + 2*ecx - 1 = 35                                               
 +
?                            ^                                               
 +
+ 3*eax - ebx + 2*ecx - 1 = 36                                               
 +
?                            ^                                               
 +
- 3*eax - ebx + 2*ecx - 1 = 413                                               
 +
?                            ^                                               
 +
+ 3*eax - ebx + 2*ecx - 1 = 414                                               
 +
?                            ^                                               
 +
139                                                                           
 +
6                                                                             
 +
1                                                                             
 +
1                                                                             
 +
4                                                                             
 +
 +
</source>
 +
<br />
 +
* The lines that do not have a prefix in front of them are the same in both the student output and the expected output.  The first 3 lines are good, and so are the last 5 lines.
 +
* The lines with a + are the expected lines, and next to them are the ones with a - and are from the submitted program.  The caret ^ shows where the difference is located.  It looks like the submitted program generates an output that is 1 lower than it should be!
 +
 +
</showafterdate>
 
<br />
 
<br />
 
<br />
 
<br />
 +
<showafterdate after="20151022 00:00" before="20151231 00:00">
 +
=Solution Program=
 +
::<source lang="asm">
 +
;;; ; hw4_func.asm
 +
;;; ; D. Thiebaut
 +
;;; ;
 +
 +
 +
;;; ; extern functions that will be linked to this program
 +
;;; ; contained in 231Lib.asm
 +
 +
        global  someFunc, computeSum, computeAvg, swap, teller
 +
       
 +
;;; ----------------------------------------------------
 +
;;; someFunc:  3*eax - ebx + 2*ecx - 1
 +
;;; ----------------------------------------------------
 +
someFunc:      mov    edx, eax
 +
                add    eax, edx
 +
                add    eax, edx
 +
                sub    eax, ebx
 +
                add    eax, ecx
 +
                add    eax, ecx
 +
                sub    eax, 1
 +
                ret
 +
       
 +
computeSum:    add    eax, ebx
 +
                add    eax, ecx
 +
                add    eax, edx
 +
                ret
 +
 +
computeAvg:    call    computeSum
 +
                mov    edx, 0
 +
                mov    ebx, 4
 +
                div    ebx
 +
                ret
 +
 +
swap:          mov    ecx, eax
 +
                mov    eax, ebx
 +
                mov    ebx, ecx
 +
                ret
 +
 +
                section .data
 +
x              dd      0
 +
n20            dd      0
 +
n10            dd      0
 +
n5              dd      0
 +
n1              dd      0
 +
       
 +
                section .text
 +
teller:        mov    dword[x], eax
 +
                mov    ebx, 20
 +
                mov    edx, 0
 +
                div    ebx
 +
                mov    dword[n20], eax
 +
       
 +
                mov    eax, edx
 +
                mov    edx, 0
 +
                mov    ebx, 10
 +
                div    ebx
 +
                mov    dword[n10], eax
 +
 +
                mov    eax, edx
 +
                mov    edx, 0
 +
                mov    ebx, 5
 +
                div    ebx
 +
                mov    dword[n5], eax
 +
                mov    dword[n1], edx
 +
 +
                mov    eax, dword[n20]
 +
                mov    ebx, dword[n10]
 +
                mov    ecx, dword[n5]
 +
                mov    edx, dword[n1]
 +
                ret
 +
 +
 +
</source>
 +
</showafterdate>
 
<br />
 
<br />
 
<br />
 
<br />

Latest revision as of 15:25, 15 October 2015

--D. Thiebaut (talk) 19:11, 14 October 2015 (EDT)



This assignment is due on Wednesday, Oct. 21, at 11:55 p.m.


<showafterdate after="20151014 12:00" before="20151231 00:00">

Preparation


  • Make sure you have a file in your working directory that contains 231Lib.asm, a library with functions for printing various quantities, as well as for inputting numbers.
  • Create 2 different programs in your working directory, one called hw4_func.asm, and the other called hw4.asm, and copy the code below into both of them:


  • hw4.asm:
;;; ; hw4.asm
;;; ; D. Thiebaut
;;; ;
;;; ; Demo program for Homework 4

;;; ; extern functions that will be linked to this program
;;; ; contained in 231Lib.asm and hw4_func.asm

        extern  _printDec
        extern  _printString
        extern  _println
        extern  _getInput
        extern  demoFunc                

;;; -----------------------------------------------------------
		section	.data
a               dd      3
msg3            db      "eax = "
MSG3LEN         equ     $-msg3


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

        ;; print "eax = "
                mov     ecx, msg3
                mov     edx, MSG3LEN
                call    _printString

        ;; print contents of eax, which contains a
                mov     eax, dword[a]
                call    _printDec
                call    _println

        ;; pass a to demoFunc through eax
                mov     eax, dword[a]
                call    demoFunc

        ;; print "eax = "
                mov     ecx, msg3
                mov     edx, MSG3LEN
                call    _printString

        ;; print contents of eax, as returned by demoFunc
                call    _printDec
                call    _println

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


  • hw4_func.asm


;;; ; hw4_func.asm
;;; ; D. Thiebaut
;;; ; Demo program for Homework 4



        global  demoFunc        ;global, so it can be accessed
                                ; from other programs.
        
;;; ----------------------------------------------------
;;; demoFunc:  returns eax * 4 + 1
;;; ----------------------------------------------------
demoFunc:       
                add     eax, eax
                add     eax, eax
                inc     eax
                ret


  • Assemble, link, and run the programs as follows:


nasm -f elf 231Lib.asm
nasm -f elf hw4.asm
nasm -f elf hw4_func.asm
ld -melf_i386 231Lib.o hw4.o hw4_func.o -o hw4
./hw4


  • Output:
eax = 3
eax = 13
Note that the result, 13, is 4 * eax + 1, which is what the function computes, given the number it receives in eax. The result is returned in eax, as well.


Your Assignment


;;; ; hw4.asm
;;; ; D. Thiebaut
;;; ;
;;; ; Program for Homework #4

;;; ; extern functions that will be linked to this program
;;; ; contained in 231Lib.asm and in hw4_func.asm

        extern  _printDec
        extern  _printString
        extern  _println
        extern  _getInput
        extern  computeSum
        extern  computeAvg
        extern  swap
        extern  someFunc
        extern  teller
        
;;; ----------------------------------------------------------
	        section	.data
a               dd      3
b               dd      5
c               dd      7
d               dd      13
avg             dd      0
sum             dd      0
msg1            db      "average = "
MSG1LEN         equ     $-msg1
msg2            db      "sum = "
MSG2LEN         equ     $-msg2
msg3            db      "eax = "
msg4            db      "ebx = "
msg5            db      "3*eax - ebx + 2*ecx - 1 = "
MSG5LEN         equ     $-msg5
        
;;; ----------------------------------------------------------
		section	.text
		global	_start
_start:	

        ;; compute sum of a, b, c, and d
                mov     eax, dword[a]
                mov     ebx, dword[b]
                mov     ecx, dword[c]
                mov     edx, dword[d]
                call    computeSum
                mov     dword[sum], eax

                mov     ecx, msg2               ; print the result
                mov     edx, MSG2LEN
                call    _printString
                mov     eax, dword[sum]
                call    _printDec
                call    _println

        ;; compute average of a, b, c, and d
                mov     eax, dword[a]
                mov     ebx, dword[b]
                mov     ecx, dword[c]
                mov     edx, dword[d]
                call    computeAvg
                mov     dword[avg], eax
        
                mov     ecx, msg1               ; print the result
                mov     edx, MSG1LEN
                call    _printString
                mov     eax, dword[avg]
                call    _printDec
                call    _println

        ;; swap eax and ebx
        
                mov     eax, 37                 ; eax <- 37
                mov     ebx, 65                 ; ebx <- 65
                call    swap                    ; swap the two
        
                mov     ecx, msg3               ; display eax
                mov     edx, 6
                call    _printString
                call    _printDec
                call    _println
        
                mov     ecx, msg4               ; display ebx
                mov     edx, 6
                call    _printString
                mov     eax, ebx
                call    _printDec
                call    _println
        
        ;; compute 3*eax - ebx + 2*ecx - 1
                mov     eax, 10                 ; initialize
                mov     ebx, 5                  ; eax, ebx, and ecx
                mov     ecx, 6
                call    someFunc                ; eax <- 3*eax - ebx + 2*ecx - 1
        
                mov     ecx, msg5               ; display result
                mov     edx, MSG5LEN
                call    _printString
                call    _printDec
                call    _println

                mov     eax, 100                ; try new values in eax, ebx,
                mov     ebx, 5                  ; and ecx
                mov     ecx, 60
                call    someFunc
        
                mov     ecx, msg5               ; display the result
                mov     edx, MSG5LEN
                call    _printString
                call    _printDec
                call    _println        

        ;; break down some amount of $ in $20-, $10-, $5-, and $1-bills
                mov     eax, 139                ; orginal amount of $
                call    _printDec               ; display it
                call    _println
        
                call    teller                  ; break down in 20, 10, 5, and 1 bills
                                                ; passed back in eax, ebx, ecx, and edx.
        
                call    _printDec               ; print No20s
                call    _println
        
                mov     eax, ebx                ; print No10s
                call    _printDec
                call    _println
        
                mov     eax, ecx                ; print No5s
                call    _printDec
                call    _println
        
                mov     eax, edx                ; print No1s
                call    _printDec
                call    _println
        
;;; exit
		mov	ebx, 0
		mov	eax, 1
		int	0x80


  • Given the new contents for hw4.asm, given above, add the missing functions to hw4_func.asm so that the output of the program will become:


sum = 28
average = 7
eax = 65
ebx = 37
3*eax - ebx + 2*ecx - 1 = 36
3*eax - ebx + 2*ecx - 1 = 414
139
6
1
1
4


Submission


  • Submit your hw4_func.asm file (only, no need for hw4.asm) on Moodle, in the HW 4 PB 1 section.



Notes


Note 1


  • You are allowed to declare additional variables in your data section, if you need to. Just add a section .data block to your hw4_func.asm. Do not modify your hw4.asm, since you will not be submitting your hw4.asm. A slightly different hw4.asm will be used to test your hw4_func.asm program, passing different values to your functions to make sure they work well.


Note 2


When Moodle compares your output to the expected output, it uses the diff Linux command, which highlights differences between the two outputs by displaying lines that mismatch with a prefix. It uses a + sign in front of the lines from the expected output, and a - sign in front of the lines generated by the program just submitted. Lines that are the same in both the expected output and the output of the submitted program do not have a prefix.
Below is an example that was generated by clicking on the debug button in Moodle, instead of evaluate: 

                                                                        
 average = 7                                                                    
 eax = 65                                                                       
 ebx = 37                                                                       
 - 3*eax - ebx + 2*ecx - 1 = 35                                                 
 ?                            ^                                                 
 + 3*eax - ebx + 2*ecx - 1 = 36                                                 
 ?                            ^                                                 
 - 3*eax - ebx + 2*ecx - 1 = 413                                                
 ?                             ^                                                
 + 3*eax - ebx + 2*ecx - 1 = 414                                                
 ?                             ^                                                
 139                                                                            
 6                                                                              
 1                                                                              
 1                                                                              
 4


  • The lines that do not have a prefix in front of them are the same in both the student output and the expected output. The first 3 lines are good, and so are the last 5 lines.
  • The lines with a + are the expected lines, and next to them are the ones with a - and are from the submitted program. The caret ^ shows where the difference is located. It looks like the submitted program generates an output that is 1 lower than it should be!

</showafterdate>

<showafterdate after="20151022 00:00" before="20151231 00:00">

Solution Program

	;;; ; hw4_func.asm
	;;; ; D. Thiebaut
	;;; ;
	
	
	;;; ; extern functions that will be linked to this program
	;;; ; contained in 231Lib.asm
	
	        global  someFunc, computeSum, computeAvg, swap, teller
	        
	;;; ----------------------------------------------------
	;;; someFunc:  3*eax - ebx + 2*ecx - 1 
	;;; ----------------------------------------------------
	someFunc:       mov     edx, eax
	                add     eax, edx
	                add     eax, edx
	                sub     eax, ebx
	                add     eax, ecx
	                add     eax, ecx
	                sub     eax, 1
	                ret
	        
	computeSum:     add     eax, ebx
	                add     eax, ecx
	                add     eax, edx
	                ret
	
	computeAvg:     call    computeSum
	                mov     edx, 0
	                mov     ebx, 4
	                div     ebx
	                ret
	
	swap:           mov     ecx, eax
	                mov     eax, ebx
	                mov     ebx, ecx
	                ret
	
	                section .data
	x               dd      0
	n20             dd      0
	n10             dd      0
	n5              dd      0
	n1              dd      0
	        
	                section .text
	teller:         mov     dword[x], eax
	                mov     ebx, 20
	                mov     edx, 0
	                div     ebx
	                mov     dword[n20], eax
	        
	                mov     eax, edx
	                mov     edx, 0
	                mov     ebx, 10
	                div     ebx
	                mov     dword[n10], eax
	
	                mov     eax, edx
	                mov     edx, 0
	                mov     ebx, 5
	                div     ebx
	                mov     dword[n5], eax
	                mov     dword[n1], edx
	
	                mov     eax, dword[n20]
	                mov     ebx, dword[n10]
	                mov     ecx, dword[n5]
	                mov     edx, dword[n1]
	                ret

</showafterdate>







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