CSC231 Loop Exercises
--D. Thiebaut 11:21, 20 October 2010 (UTC)
Exercise 1
Write a loop using the LOOP instruction that prints all the numbers from 1 to 100, one per line
Exercise 2
Modify the loop so that it sums up all the numbers from 1 to 100 and prints the sum at the end.
Exercise 3
Modify the loop so that it prints all the numbers from n1 to n2, where n1 and n2 are dword variables.
Exercise 4
Modify exercise 1 so that the program prints the numbers 10 per line.
1 2 3 4 5 6 7 8 9 10 11 12 13 14... 20 21 22 23... 30 ... 91 92 93 94... 100
Exercise 5
Review. Write a simple program that prints a line of 30 stars
******************************
Exercise 6
Using a loop, write a simple program that prints 30 lines of stars, such that the first line contains 30 stars, the next one 29 stars, then 28 stars, until the last line printed contains only 1 star.
****************************** ***************************** **************************** *************************** ************************** ************************* ************************ *********************** ********************** ********************* . . . *** ** *
Exercise 7
Same exercise, but this time the first line printed contains 1 star, the next 2 stars, and so on until the last one, which contains 30 stars.
Solution 1
; print all ints between 1 and 100, one per line.
%include "asm_io.inc"
;; -------------------------
;; data segment
;; -------------------------
section .data
;; -------------------------
;; code area
;; -------------------------
section .text
global asm_main
asm_main:
mov ecx, 100
mov eax, 1
for:
call print_int
call print_nl
inc eax
loop for
ret
Solution 2
;;; loop2.asm
;;; prints all the numbers between 1 and 100
;;; sums them up
;;; displays the sum at the end.
%include "asm_io.inc"
;; -------------------------
;; data segment
;; -------------------------
section .data
;; -------------------------
;; code area
;; -------------------------
section .text
global asm_main
asm_main:
mov ecx, 100
mov eax, 1
mov ebx, 0
for: add ebx, eax
call print_int
call print_nl
inc eax
loop for
call print_nl
mov eax, ebx
call print_int
call print_nl
ret
Solution 3
;;; loop3.asm
;;; prints all the numbers between n1 and n2, sums them up, and prints
;;; the sum
%include "asm_io.inc"
;; -------------------------
;; data segment
;; -------------------------
section .data
n1 dd 10
n2 dd 20
;; -------------------------
;; code area
;; -------------------------
section .text
global asm_main
asm_main:
mov ecx, dword[n2]
sub ecx, dword[n1]
inc ecx
mov eax, dword[n1]
mov ebx, 0
for: add ebx, eax
call print_int
call print_nl
inc eax
loop for
call print_nl
mov eax, ebx
call print_int
ret
Solution 4
;;; loop4.asm
;;; same as loop1.asm, but prints the
;;; numbers 10 per line.
%include "asm_io.inc"
;; -------------------------
;; data segment
;; -------------------------
section .data
space db " ", 0
;; -------------------------
;; code area
;; -------------------------
section .text
global asm_main
asm_main:
;;; n = 1
;;; for i in range( 1, 11 ): # loops 10 times
;;; for j in range( 1, 11 ): # loops 10 times
;;; print( n, end=" " )
;;; n += 1
;;; print()
;;;
;;; n = 1
mov eax, 1
mov ecx, 10
for1: mov edx, ecx ; save ecx of loop1
mov ecx, 10
for2: call print_int ; print n
mov ebx, eax ; save n
mov eax, space ; print space
call print_string
mov eax, ebx ; restore n
inc eax ; n <- n+1
loop for2
call print_nl
mov ecx, edx
loop for1
call print_nl
ret
Solution 6
;;; printStars.asm
;;; D. Thiebaut
;;;
;;;
;;;
;;; To assemble, link, and run:
;;; nasm -f elf -F stabs printStars.asm
;;; ld -melf_i386 -o printStars printStars.o
;;; ./printStars
;;;
section .data
stars db 0x0a, "******************************"
starsLen equ $-stars
addr dd stars
count dd starsLen
section .text
global _start
_start:
mov ecx, dword[count]
for: mov dword[count], ecx
mov eax, 4
mov ebx, 1
mov ecx, stars
mov edx, dword[count]
int 0x80
mov ecx, dword[count]
loop for
;;; exit
mov ebx, 0
mov eax, 1
int 0x80
