Difference between revisions of "CSC231 Addressing Mode Exercises"
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| − | =Exercises on Addressing Modes= | + | =Exercises on Addressing Modes and Loops= |
| + | <br /> | ||
| + | <!--(Highlight the boxes to see one possible solution...)--> | ||
| + | ==Exercise 1== | ||
| + | <br /> | ||
| + | Indicate the addressing used by each of the instructions below. | ||
| + | <br /> | ||
| + | <source lang="asm"> | ||
| − | + | ;;; ------------------------------------------------------------ | |
| − | + | ;;; Identify possible errors in the instructions below, and | |
| + | ;;; indicate the addressing mode for each one. | ||
| + | ;;; ------------------------------------------------------------ | ||
| + | |||
| + | section .data | ||
| + | a db 3 | ||
| + | b db 0x12345678 | ||
| + | c dw 0 | ||
| + | x dd 30 | ||
| + | array dd 1,2,3,4,5,6,7,8,9,10 | ||
| + | |||
| + | section .text | ||
| + | global _start | ||
| − | + | _start: mov eax, a | |
| − | + | mov eax, dword[a] ; is it an error? | |
| − | + | mov ebx, array | |
| − | + | mov eax, dword[ebx] | |
| + | mov esi, 0 | ||
| + | mov dword[ebx+esi], 0 | ||
| + | mov dword[ebx+esi+4], eax | ||
| + | mov edi, b | ||
| + | mov byte[edi], 'Z' | ||
| + | add al, 'z'-'Z' | ||
| + | mov ecx, 10 | ||
| + | for: inc ecx | ||
| + | loop for | ||
| + | |||
| + | ;;; exit() | ||
| − | + | mov eax,1 | |
| − | + | mov ebx,0 | |
| − | + | int 0x80 ; final system call | |
| − | |||
| − | |||
| − | </ | + | </source> |
| − | </ | + | <br /> |
==Exercise 2== | ==Exercise 2== | ||
| − | Write a program that | + | Write a program that changes all the characters of an all-uppercase string to all-lowercase. We assume the string does not contain blank spaces. You can find an ASCII table [http://www.asciitable.com/ here]. |
| − | < | + | |
| + | <!-- | ||
| + | msg db "HELLOTHEREHOWAREYOU" | ||
| + | MSGLEN equ $-msg | ||
| + | |||
| + | mov ebx, msg ; ebx points to 1st char of msg | ||
| + | mov ecx, MSGLEN ; # of chars in string | ||
| + | for: sub byte[ebx],32 ; lower to upper case, in memory | ||
| + | inc ebx ; ebx points to next char | ||
| + | loop for | ||
| + | --> | ||
| + | |||
| + | ==Exercise 3== | ||
| + | Write a program that fills an array of 8 bytes with the first 8 powers of 2: 1, 2, 4, 8, 16, etc. | ||
| + | |||
| + | <!-- | ||
<code><pre> | <code><pre> | ||
fib db 1, 1, 0, 0, 0, 0, 0, 0 | fib db 1, 1, 0, 0, 0, 0, 0, 0 | ||
| Line 35: | Line 78: | ||
loop for ; go back | loop for ; go back | ||
</pre></code> | </pre></code> | ||
| − | + | --> | |
| − | ==Exercise | + | ==Exercise 4== |
Write a program that fills an array of 16 words with the first 16 fibonacci terms | Write a program that fills an array of 16 words with the first 16 fibonacci terms | ||
| − | < | + | |
| + | <!-- | ||
<code><pre> | <code><pre> | ||
fib dw 1, 1, 0, 0, 0, 0, 0, 0 | fib dw 1, 1, 0, 0, 0, 0, 0, 0 | ||
| Line 54: | Line 98: | ||
loop for ; go back | loop for ; go back | ||
</pre></code> | </pre></code> | ||
| − | + | --> | |
| + | |||
| + | ==Exercise 5== | ||
| − | |||
Write a program that fills an array of 10 double-words with the first 10 powers of 2. | Write a program that fills an array of 10 double-words with the first 10 powers of 2. | ||
| − | < | + | <!-- |
<code><pre> | <code><pre> | ||
Powers dd 0,0,0,0,0,0,0,0,0,0 | Powers dd 0,0,0,0,0,0,0,0,0,0 | ||
| Line 74: | Line 119: | ||
loop for ; go 9 times | loop for ; go 9 times | ||
</pre></code> | </pre></code> | ||
| − | + | --> | |
| − | ==Exercise | + | ==Exercise 6== |
| − | + | The example below copies a string into another string, reversing the order of the string (to see if the original string is a palindrome, for example). Rewrite it using a ''based indexed'' addressing mode. | |
| + | |||
| + | <!-- | ||
| + | msg1 db "Esope reste ici et se repose" | ||
| + | msg2 db " " | ||
| + | MSGLEN equ $-msg2 | ||
| + | |||
| + | mov esi, msg1 | ||
| + | mov edi, msg2 | ||
| + | mov ecx, MSGLEN | ||
| − | + | for mov al, byte[esi] | |
| − | + | mov byte[edi], al | |
| + | inc esi | ||
| + | inc edi | ||
| + | loop for | ||
| + | |||
| + | --> | ||
Latest revision as of 06:22, 2 October 2014
Contents
Exercises on Addressing Modes and Loops
Exercise 1
Indicate the addressing used by each of the instructions below.
;;; ------------------------------------------------------------
;;; Identify possible errors in the instructions below, and
;;; indicate the addressing mode for each one.
;;; ------------------------------------------------------------
section .data
a db 3
b db 0x12345678
c dw 0
x dd 30
array dd 1,2,3,4,5,6,7,8,9,10
section .text
global _start
_start: mov eax, a
mov eax, dword[a] ; is it an error?
mov ebx, array
mov eax, dword[ebx]
mov esi, 0
mov dword[ebx+esi], 0
mov dword[ebx+esi+4], eax
mov edi, b
mov byte[edi], 'Z'
add al, 'z'-'Z'
mov ecx, 10
for: inc ecx
loop for
;;; exit()
mov eax,1
mov ebx,0
int 0x80 ; final system call
Exercise 2
Write a program that changes all the characters of an all-uppercase string to all-lowercase. We assume the string does not contain blank spaces. You can find an ASCII table here.
Exercise 3
Write a program that fills an array of 8 bytes with the first 8 powers of 2: 1, 2, 4, 8, 16, etc.
Exercise 4
Write a program that fills an array of 16 words with the first 16 fibonacci terms
Exercise 5
Write a program that fills an array of 10 double-words with the first 10 powers of 2.
Exercise 6
The example below copies a string into another string, reversing the order of the string (to see if the original string is a palindrome, for example). Rewrite it using a based indexed addressing mode.
