CSC231 Homework 1 Solution 2014
--D. Thiebaut (talk) 07:55, 9 October 2014 (EDT)
Problem 2
;;; ; hw1_2.asm
;;; ; D. Thiebaut
;;; ;
;;; ; Displays a triangle of As and Bs:
;;; ; A
;;; ; AA
;;; ; AAA
;;; ; AAAA
;;; ; AAAAA
;;; ; BBBBB
;;; ; BBBB
;;; ; BBB
;;; ; BB
;;; ; B
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ; nasm -f elf -F stabs hw1_2.asm
;;; ; nasm -f elf -F stabs 231Lib.asm
;;; ; ld -melf_i3896 -o hw1_2 hw1_2.o 231Lib.o
;;; ; ./hw1_2
;;; ; -------------------------------------------------------------------
;;; ------------------------------------------------------------
;;; data areas
;;; ------------------------------------------------------------
section .data
msg db "AAAAA", 10
;;; ------------------------------------------------------------
;;; code area
;;; ------------------------------------------------------------
section .text
global _start
_start:
mov ecx, msg+4 ;print A
mov edx, 2
call printStr
mov ecx, msg+3 ;print AA
mov edx, 3
call printStr
mov ecx, msg+2 ;print AAA
mov edx, 4
call printStr
mov ecx, msg+1 ;print AAAA
mov edx, 5
call printStr
mov ecx, msg ;print AAAAA
mov edx, 6
call printStr
inc byte [msg] ;msg now contains BAAAA
inc byte [msg+1] ;msg now contains BBAAA
inc byte [msg+2] ;msg now contains BBBAA
inc byte [msg+3] ;msg now contains BBBBA
inc byte [msg+4] ;msg now contains BBBBB
mov ecx, msg ;print BBBBB
mov edx, 6
call printStr
mov ecx, msg+1 ;print BBBB
mov edx, 5
call printStr
mov ecx, msg+2 ;print BBB
mov edx, 4
call printStr
mov ecx, msg+3 ;print BB
mov edx, 3
call printStr
mov ecx, msg+4 ;print B
mov edx, 2
call printStr
;;; exit()
mov eax,1
mov ebx,0
int 0x80 ; final system call
;;; ----------------------------------------------------------
;;; Function: print string
;;; gets address of string in ecx
;;; gets length of string in edx
;;; MODIFIED REGISTERS: eax, ebx
printStr: mov eax, 4
mov ebx, 1
int 0x80
ret
