CSC231 Addressing Mode Exercises
Contents
Exercises on Addressing Modes
(Highlight the boxes to see one possible solution...)
Exercise 1
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
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 2
Write a program that fills an array of 8 bytes with the first 8 fibonacci terms
fib db 1, 1, 0, 0, 0, 0, 0, 0
NOFIB equ $-fib
mov ebx, fib
mov esi, 2 ; point to Fib[3]
mov ecx, NOFIB-2 ; skip first 2 Fibs
mov al, byte[ebx+esi-1] ;
for: add al, byte[ebx+esi-2]
mov byte[ebx+esi], al ; fib_i = fib_i-1 + fib_i-2
inc esi ; point to next uncomputed fib
loop for ; go back
Exercise 3
Write a program that fills an array of 16 words with the first 16 fibonacci terms
fib dw 1, 1, 0, 0, 0, 0, 0, 0
NOFIB equ ($-fib)/2
mov ebx, fib
mov esi, 2*2 ; point to Fib[3]
mov ecx, NOFIB-2*2 ; skip first 2 Fibs
mov al, byte[ebx+esi-1*2] ;
for: add al, byte[ebx+esi-2*2]
mov byte[ebx+esi], al ; fib_i = fib_i-1 + fib_i-2
add esi,2 ; point to next uncomputed fib
loop for ; go back
Exercise 4
Write a program that fills an array of 10 double-words with the first 10 powers of 2.
Powers dd 0,0,0,0,0,0,0,0,0,0
NOPOW equ ($-Powers)/4
mov ebx, Powers ; ebx points to powers
mov eax, 1
mov dword[ebx], eax ; 2^0
mov ecx, NOPOW-1 ; ready to loop 9 times
for: shl eax, 1 ; multiply eax by 2, store in next
mov dword[ebx], eax ; cell of array
add ebx, 4 ; point to next empty cell
loop for ; go 9 times
Exercise 5
Assume an array of 11 words, and the first words contains a constant. Write the program that stores 1/2 the value of the constant in the 2nd word, 1/4 the value in the 3rd word, 1/8 4th word, 1/16 5th word, etc.
Powers dd 57,0,0,0,0,0,0,0,0,0
NOPOW equ ($-Powers)/4
mov ebx, Powers ; ebx points to powers
mov eax, dword[ebx]; get first dword
mov ecx, NOPOW-1 ; ready to loop 9 times
for: shr eax, 1 ; multiply eax by 2, store in next
add ebx, 4 ; point to next empty cell
mov dword[ebx], eax ; cell of array
loop for ; go 9 times
Exercise 6
Copy a string into another string, reversing the order of the string to see if they are palindromes.
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
