Difference between revisions of "CSC231 Homework Solutions 2017"

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--[[User:Thiebaut|D. Thiebaut]] ([[User talk:Thiebaut|talk]]) 17:57, 22 April 2017 (EDT)
 
--[[User:Thiebaut|D. Thiebaut]] ([[User talk:Thiebaut|talk]]) 17:57, 22 April 2017 (EDT)
 
----
 
----
 +
<onlydft>
 
=Problem 1=
 
=Problem 1=
 
::<source lang="asm">
 
::<source lang="asm">
Line 321: Line 322:
 
<br />
 
<br />
 
::<source lang="asm">
 
::<source lang="asm">
−
;;; ; program_name.asm
+
;;; ; hw5_1.asm
−
;;; ; your name
+
;;; ; D. Thiebaut
 
;;; ;
 
;;; ;
−
;;; ; a description of the program
+
;;; ; Prints 10 lines of Pascal triangle.
 
;;; ;
 
;;; ;
 
;;; ; to assemble and run:
 
;;; ; to assemble and run:
 
;;; ;
 
;;; ;
−
;;; ;    nasm -f elf -F  stabs program.asm
+
;;; ;    nasm -f elf -F  stabs hw5_1.asm
−
;;; ;    ld -melf_i386 -o program program.o
+
;;; ;    ld -melf_i386 -o hw5_1 hw5_1.o
−
;;; ;    ./program
+
;;; ;    ./hw5_1
 
;;; ; -------------------------------------------------------------------
 
;;; ; -------------------------------------------------------------------
  
Line 412: Line 413:
 
</source>
 
</source>
 
<br />
 
<br />
 +
 
=hw5_2.sh=
 
=hw5_2.sh=
 
<br />
 
<br />
Line 448: Line 450:
 
done
 
done
 
</source>
 
</source>
 +
<br />
 +
=GameOfLife.asm=
 +
::<source lang="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
 +
 +
</source>
 +
<br />
 +
=hw7_1.C=
 +
<br />
 +
::<source lang="C">
 +
#include <stdio.h>
 +
#include <stdlib.h>
 +
#include <string.h>
 +
 +
int main( int argc, char *argv[] ) {
 +
  int n, i, name;
 +
  char sentence[100];
 +
  char stars[100];
 +
 +
  if ( argc < 2 ) {
 +
    printf( "Syntax: %s string [string...]\n", argv[0] );
 +
    exit( 1 );
 +
  }
 +
 +
  strcpy( sentence, "* " );
 +
  for ( i = 1; i < argc; i++ ) {
 +
    if ( i > 1 )
 +
      strcat( sentence, " " );
 +
    strcat( sentence, argv[i] );
 +
  }
 +
  strcat( sentence, " *" );
 +
 +
  // printf( "%s\n", sentence );
 +
 +
  n = (int) strlen( sentence );
 +
 +
  strcpy( stars, "*" );
 +
  for ( i=0; i<strlen( stars)-1; i++ )
 +
    strcat( stars, "*" );
 +
 +
  for ( i=0; i< n-1; i++ ) {
 +
    stars[i+1] = '\0';
 +
    printf( "%s\n", stars );
 +
    stars[i+1] = '*';
 +
  }
 +
 +
  printf( "%s\n", sentence );
 +
 +
  for ( i=n-2; i>= 0; i-- ) {
 +
    stars[i+1] = '\0';
 +
    printf( "%s\n", stars );
 +
    stars[i+1] = '*';
 +
  }
 +
 +
 +
  return 0;
 +
}
 +
</source>
 +
<br />
 +
=hw7_2.asm=
 +
<br />
 +
::<source lang="asm">
 +
;;; ; -------------------------------------------------------------------
 +
;;; ; hw4b.asm
 +
;;; ; Julia Burch
 +
;;; ; 231a-aa
 +
;;; ;
 +
;;; ; Computes and prints the first 10 rows of Pascal's triangle.
 +
;;; ; OUTPUT:
 +
;;; ;  1        0      0      0      0      0      0      0      0      0
 +
;;; ;  1        1      0      0      0      0      0      0      0      0
 +
;;; ;  1        2      1      0      0      0      0      0      0      0
 +
;;; ;  1        3      3      1      0      0      0      0      0      0
 +
;;; ;  1        4      6      4      1      0      0      0      0      0
 +
;;; ;  1        5      10      10      5      1      0      0      0      0
 +
;;; ;  1        6      15      20      15      6      1      0      0      0
 +
;;; ;  1        7      21      35      35      21      7      1      0      0
 +
;;; ;  1        8      28      56      70      56      28      8      1      0
 +
;;; ;  1        9      36      84      126    126    84      36      9      1
 +
;;; ; to assemble and run:
 +
;;; ;
 +
;;; ;    nasm -f elf -F  stabs hw4b.asm
 +
;;; ;    gcc -o hw4b driver.c asm_io.o hw4b.o
 +
;;; ;    ./hw4b
 +
;;; ; -------------------------------------------------------------------
 +
 +
        ;; %include files here...
 +
extern _printDec
 +
extern  _println
 +
extern  _printString
 +
 +
;;;  ------------------------------------------------------------
 +
;;;  data areas
 +
;;;  ------------------------------------------------------------
 +
 +
        section .data
 +
 +
        shift    db    0
 +
        pascal  db    1, 0, 0, 0, 0, 0, 0, 0, 0, 0
 +
        temp    dd    0
 +
        space    db    9
 +
        rows    equ    10
 +
;;;  ------------------------------------------------------------
 +
;;;  code area
 +
;;;  ------------------------------------------------------------
 +
 +
        section .text
 +
        global  _start
 +
 +
_start:
 +
 +
        ;; move first line of Pascal into edi, then rows into ecx
 +
        ;; to initialize and run for loop 10 times.
 +
        mov    edi, pascal
 +
        mov    ecx, rows
 +
main:
 +
        ;; store ecx in a temporary variable, move rows into ecx to initialize
 +
        ;; and run print_triangle loop. Move the first line into edi
 +
        ;; and 0 into esi.
 +
        push ecx
 +
        mov    ecx, rows
 +
        mov    edi, pascal
 +
        mov    esi, 0
 +
 +
print_triangle:
 +
        ;; print the int in al, print tab and then clear
 +
        ;; tab from register.
 +
push ecx
 +
        mov    al, byte[edi+esi]
 +
        call    _printDec
 +
 +
        mov    ecx, space
 +
mov    edx, 1
 +
        call    _printString
 +
 +
        mov    eax, 0
 +
        inc    esi
 +
 +
pop ecx
 +
        loop print_triangle
 +
 +
        ;; print a new line
 +
        call    _println
 +
 +
        ;; load newly calculated pascal line into edi, then shift the row
 +
        mov    edi, pascal
 +
        mov    esi, shift
 +
        mov    ecx, rows-1
 +
 +
calculate:
 +
        ;; move pascal digit into al, add it to previous row's, store the value
 +
        mov    al, byte[edi+ecx]
 +
        add    al, byte[esi+ecx]
 +
        mov    byte[edi+ecx], al
 +
 +
        loop calculate
 +
 +
        ;; restore value of ecx for loop
 +
pop ecx
 +
        loop main
 +
 +
;;;  exit()
 +
        mov ebx, 0
 +
mov eax, 1
 +
int 0x80
 +
 +
</source>
 +
<br />
 +
=hw7_3.asm (mystery program)=
 +
<br />
 +
::<source lang="asm">
 +
 +
;;; helloWorld.asm
 +
;;; D. Thiebaut 
 +
;;;               
 +
;;; To assemble, link, and run: 
 +
;;;    nasm -f elf  helloWorld.asm 
 +
;;;    ld -melf_i386 -o helloWorld helloWorld.o
 +
;;;    ./helloWorld       
 +
;;;     
 +
 +
                section .data
 +
db "Mystery", 0
 +
msg1 db      "Vive le chacalot au lait!", 0
 +
msg2            db      "Assembly is fun!", 0
 +
msg3 db 0x01, 0x02, 0x03
 +
x dd 128
 +
y dd 64
 +
HelloLen        equ    $-msg1
 +
 +
                section .text
 +
 +
_mystery:
 +
 +
;;; print message
 +
        add byte[msg1+10],'o'-'a'
 +
add byte[msg1+12],'o'-'a'
 +
add byte[msg1+14],'a'-'o'
 +
                mov    eax, 4          ; write   
 +
                mov    ebx, 1          ; stdout 
 +
                mov    ecx, msg1+8
 +
                mov    edx, 8          ; # of chars to print 
 +
                int    0x80
 +
 +
mov eax, dword[x]
 +
add eax, 0xFFFFFFFF
 +
xor ebx, ebx
 +
mov bx, word[y]
 +
shl bx,16
 +
mov edx, 0x12345678
 +
mov dx, ax
 +
mov ecx, 10
 +
loop there
 +
there:
 +
 +
;;; exit                                                                                                                                   
 +
                mov    ebx, 0
 +
                mov    eax, 1
 +
                int    0x80
 +
</source>
 +
<!-- ========================================================= -->
 +
<br />
 +
=hw8_1.c=
 +
<br />
 +
::<source lang="C">
 +
#include <stdio.h>
 +
#include <stdlib.h>
 +
#include <string.h>
 +
 +
 +
void main( int argc, char *argv[] ) {
 +
  char *marker1, *marker2, *DNA;
 +
  char *fileName;
 +
 +
  if (argc < 4 ) {
 +
    printf( "syntax: %s marker1 marker2 DNA\n", argv[0] );
 +
    return;
 +
  }
 +
 +
  marker1 = argv[1];
 +
  marker2 = argv[2];
 +
  DNA    = argv[3];
 +
 
 +
  //--- print the markers and DNA ---
 +
  /* (for debugging purposes)
 +
  printf( "Marker1 = %s\n", marker1 );
 +
  printf( "Marker2 = %s\n", marker2 );
 +
  if ( strlen( DNA ) > 80 )
 +
    printf( "DNA    = %.*s...%s (%d bases)\n\n",
 +
          10, DNA, DNA+((int)strlen(DNA)-10),
 +
  (int) strlen( DNA) );
 +
  else
 +
    printf( "DNA    = %s\n\n", DNA );
 +
  */
 +
 +
  //--- add your code below this point ---
 +
  char *first, *second;
 +
  first = strstr( DNA, marker1 );
 +
  if ( first == NULL ) {
 +
    printf( "%s\n", DNA );
 +
    return;
 +
  }
 +
  second = strstr( first+1, marker2 );
 +
  if ( second == NULL ) {
 +
    printf( "%s\n", DNA );
 +
    return;
 +
  }
 +
 
 +
  char *p;
 +
  for ( p= first; p < second+strlen(marker2); p++ )
 +
    *p = '-';
 +
 +
  printf( "%s\n", DNA );
 +
}
 +
 +
</source>
 +
=hw8_2.asm=
 +
<br />
 +
::<source lang="asm">
 +
; hw8_2.asm
 +
; D. Thiebaut
 +
 +
global f1
 +
global f2
 +
global f3
 +
 +
;;; ------------------------------------------------------
 +
;;; f1( s ): modifies s in place and make it uppercase.
 +
f1: push ebp
 +
mov ebp, esp
 +
push ebx
 +
mov ebx, dword[ebp+8]
 +
.for: cmp byte[ebx], 0
 +
je .done
 +
cmp byte[ebx],'a'
 +
jl .endfor
 +
cmp byte[ebx],'z'
 +
jg .endfor
 +
add byte[ebx],'A'-'a'
 +
.endfor:
 +
inc ebx
 +
jmp .for
 +
.done:
 +
pop ebx
 +
pop ebp
 +
ret 4
 +
 +
;;; ------------------------------------------------------
 +
;;; f2( a, b, c )
 +
;;; returns 2a + 3b -c in eax
 +
;;; computes it as 2(a+b) + b - c (fewer operations)
 +
f2: push ebp
 +
mov ebp, esp
 +
mov eax, dword[ebp+8+4+4] ; get first param
 +
add eax, dword[ebp+8+4]  ; eax <- a+b
 +
add eax, eax       ; eax <- 2(a+b)
 +
add eax, dword[ebp+8+4]  ; eax <- 2(a+b) + b
 +
sub eax, dword[ebp+8]    ; eax <- 2a + 3b -c
 +
pop ebp       ;
 +
ret 4*3       ; return and get rid of 3 ints
 +
 +
 +
;;; ------------------------------------------------------
 +
;;; f3( array, n )
 +
;;; computes the number of even ints in array, of length n.
 +
;;; returns this number in eax.
 +
f3: push ebp
 +
mov ebp, esp
 +
 +
;;; push ebx
 +
push ecx
 +
 +
mov ebx, dword[ebp+8+4] ; ebx <- array
 +
mov ecx, dword[ebp+8] ; ecx <- n
 +
mov eax, 0 ; number of even ints
 +
.for: and dword[ebx], 1 ; and array[i] with 1
 +
jnz .notEven ; if result is 1, then odd number
 +
.even: inc eax ; otherwise, add 1 to counter.
 +
.notEven:
 +
add ebx, 4
 +
loop .for
 +
 +
;;; pop ecx
 +
pop ebx
 +
 +
pop ebp
 +
ret 2*4
 +
 +
 +
</source>
 +
<!-- ================================================================= -->
 +
 +
=Homework 9: funcs.c=
 +
<br />
 +
::<source lang="c">
 +
#include <stdio.h>
 +
#include <stdlib.h>
 +
#include <string.h>
 +
 +
// getMax: returns the largest of 3 integers passed
 +
// by value
 +
int getMin( int a, int b, int c ) {
 +
  if ( a <= b && a <= c )
 +
    return a;
 +
  if ( b <= a && b <= c )
 +
    return b;
 +
  return c;
 +
}
 +
 +
// zap: given a string haystack, and a string needle,
 +
// looks for the firlst location of needle in the haystack, and
 +
// when it finds it, replaces it with dashes.  Example
 +
// char s1[] = "Mississippi";
 +
// char s2[] = "ss";
 +
// char *p  = s1, *q = s2;
 +
// zap( s1, s2 ) will replace s1 with "Mi--issippi".
 +
// zap( s1, "mm" ) will leave s1 unchanged.
 +
// Returns 0 if zap couldn't fine the needle in
 +
// the haystack.  Returns 1 if some character replacement
 +
// took place.
 +
int zap( char *haystack, char *needle ) {
 +
  char *p = strstr( haystack, needle );
 +
  char *q;
 +
  if ( p==NULL )
 +
    return 0;
 +
  for ( q=p; q != p+strlen( needle ); q++ )
 +
    *q = '-';
 +
  return 1;
 +
}
 +
 +
// merge(): takes two sorted arrays of ints of length 5
 +
// and merges them into an array of length 10, so that
 +
// the third array is sorted, in increasing order.
 +
void merge( int A[], int B[], int C[] ) {
 +
  int i = 0;
 +
  int j = 0;
 +
  int k = 0;
 +
  while ( 1 ) {
 +
    if ( A[i] < B[j] ) {
 +
      C[k++] = A[i++];
 +
      //printf( "A[%d] (%d) < B[%d] (%d) ==> C[%d] (%d)\n", i-1, A[i-1], j, B[j], k-1, C[k-1] );
 +
    }
 +
    else {
 +
      C[k++] = B[j++];
 +
      //printf( "A[%d] (%d) > B[%d] (%d) ==> C[%d] (%d)\n", i, A[i], j-1, B[j-1], k-1, C[k-1] );
 +
    }
 +
    if ( i>=5 || j>=5 )
 +
      break;
 +
  } 
 +
 +
  while ( i<5 && k <10 ) {
 +
    C[k++] = A[i++];
 +
    //printf( "C[%d] (%d) <--  A[%d] (%d)\n", k-1, C[k-1], i-1, A[i-1] );
 +
  }
 +
  while ( j<5 && k <10 ) {
 +
    C[k++] = B[j++]; 
 +
    //printf( "C[%d] (%d) <--  B[%d] (%d)\n", k-1, C[k-1], j-1, B[j-1] );
 +
 +
  }
 +
}
 +
</source>
 +
=Homework 9: hanoi.asm=
 +
<br />
 +
::<source lang="asm">
 +
;;; hanoi.asm
 +
;;; D. Thiebaut 
 +
;;;
 +
;;; This program solves the "Towers of Hanoi" program
 +
;;; in assembly.  It prompts the user for an integer
 +
;;; number of disks (must be larger than 0) and displays
 +
;;; the name of the peg from which to move a disk, and
 +
;;; the name of the peg to move it to.  The pegs are
 +
;;; labeled 'A', 'B', and 'C', and the disks are always
 +
;;; assumed to moved originally from 'A' to 'B'.
 +
;;; To assemble, link, and run:
 +
;;;    nasm -f elf  231Lib.o
 +
;;;    nasm -f elf  hanoi.asm 
 +
;;;    ld -melf_i386 -o hanoi hanoi.o 231Lib.o
 +
;;;    ./hanoi  3   
 +
;;;     
 +
 +
                section .data
 +
N dd 5
 +
 +
                section .text
 +
extern _getInput
 +
extern _println
 +
extern _printString
 +
extern _atoi
 +
        global  _start
 +
_start:
 +
 +
;;; get N from command line
 +
;;; When any assembly language program starts, the operating system
 +
;;; passes it argc and argv through the statck.  The esp register
 +
;;; points to argc.  at esp+4, is a pointer to the beginning of argv[0],
 +
;;; as a string.  At esp+8 is a pointer to the beginning of argv[1],
 +
;;; as a string.
 +
 +
mov ebp, esp
 +
mov eax, dword[ebp]     ; put argc into eax
 +
;;; call _printDec     ; print it
 +
;;; call _println
 +
 +
mov eax, dword[ebp+4+4] ; make eax points to arv[1]
 +
call _atoi     ; convert ascii string to int
 +
mov dword[N], eax     ; save N
 +
 +
 +
;;; define the 3 pegs and pass them in bl, cl, and dl.
 +
 +
mov bl, 'A'
 +
mov cl, 'B'
 +
mov dl, 'C'
 +
 +
;;; moveDisks( N, 'A', 'B', 'C' )      ; eax <- N
 +
call moveDisks ; bl  <- 'A'
 +
; cl  <- 'B'
 +
; dl  <- 'C'
 +
 +
 +
;;; exit
 +
                mov    ebx, 0
 +
                mov    eax, 1
 +
                int    0x80
 +
 +
 +
;;; ------------------------------------------------------------------
 +
;;; moveDisks( n, source, dest, extra )
 +
;;;          eax  bl    cl    dl
 +
;;; Moves the n disks from source to dest using extra if necessary.
 +
;;; Uses recursion to move the N-1 disks above the last one.
 +
;;; Does not modify any of the registers
 +
;;; ------------------------------------------------------------------
 +
moveDisks: pushad
 +
 +
;;; if n==1:
 +
;;;    print( source, dest )
 +
cmp eax, 1
 +
jg recurse
 +
mov al, bl ; print source
 +
call printChar
 +
mov al, ' ' ; print space
 +
call printChar
 +
mov al, cl ; print dest
 +
call printChar
 +
call _println ; print \n
 +
 +
popad ; done! return
 +
ret
 +
 +
recurse:
 +
;;; moveDisks( n-1, source, temp, dest )
 +
dec eax ; eax <- n-1
 +
xchg cl, dl ; swap cl & dl
 +
call moveDisks      ; move n-1
 +
xchg cl, dl ; swap them back
 +
 +
 +
;;; print( source, dest )
 +
                mov    al, bl ; print source
 +
call    printChar
 +
mov    al, ' ' ; print space
 +
        call    printChar
 +
        mov    al, cl ; print dest
 +
        call    printChar
 +
        call    _println ; print \n
 +
 +
;;; moveDisks( n-1, temp, dest, source )
 +
                popad                      ; get all the original parameters back
 +
                pushad                      ; and push them back in the stack
 +
                xchg    bl, dl              ; exchange source and temp
 +
                dec    eax                ; eax <-- n-1
 +
                call    moveDisks          ; recurse
 +
 +
                popad                      ; pop all registers back
 +
                ret
 +
 +
;;; ------------------------------------------------------------------
 +
;;; printChar: prints the character in al
 +
;;; does not modify any other register
 +
;;; ------------------------------------------------------------------
 +
section .data
 +
char db 'A'
 +
section .text
 +
printChar: pushad
 +
mov byte[char],al
 +
mov ecx, char
 +
mov edx, 1
 +
call _printString
 +
popad
 +
ret
 +
 +
 +
 +
</source>
 +
</onlydft>
 +
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 +
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 +
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 +
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[[Category:CSC231]][[Category:Homework]]

Latest revision as of 16:55, 16 September 2017

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


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