CSC231 Addressing Mode Exercises

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.