CSC231 Homework 3 2014

--D. Thiebaut (talk) 15:17, 29 September 2014 (EDT)

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Preparation

Looping. Version 1

• Create the following program in your beowulf2 directory:

;;; ; loop1.asm
;;; ; D. Thiebaut
;;; ;
;;; ; a simple program using a loop in which the ecx
;;; ; register is printed.
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ;     nasm -f elf loop1.asm
;;; ;     nasm -f elf 231Lib.asm
;;; ;     ld -melf_i3896 -o loop1 loop1.o 231Lib.o
;;; ;     ./loop1
;;; ; -------------------------------------------------------------------

extern _printDec                       ; the function that prints eax in decimal
extern _println                          ; the function that brings the cursor to the next line.

;;;  ------------------------------------------------------------
;;;  code area
;;;  ------------------------------------------------------------

                section .text
                global  _start

_start:
                mov     ecx, 10
for:            mov     eax, ecx
                call    _printDec
                call    _println
                loop    for

;;;  exit()

                mov     eax,1
                mov     ebx,0
                int     0x80    ; final system call

• Run it.
• Verify that it displays the different values of ecx, the loop counter.