CSC231 Homework 6 2017

--D. Thiebaut (talk) 18:56, 1 April 2017 (EDT)

---

Game Of Life Without Loop Instructions

For this assignment, you need to write a game of life program in assembly, and the challenge is to implement it without using the loop instruction, using only the cmp instruction and conditional jumps.

Problem Statement

Write an assembly language program similar to the one with work out in class, but with a few differences, listed below. You can find the program we wrote in class here.

• Your program will use an include file to get the array dish, which contains the initial 1-line generation of cells.
• Your program will not use a single loop instruction, and will implement all the loops using cmp and jump instructions (conditionals and unconditional jumps will be used).

Using an Include File

The concept is simple: you put part of the code into a separate file, and you use an "%include" statement inside the main program to tell nasm that it should read the contents of the include file as part of this program.
The code below illustrates how this is done. We have two files:

GameOfLifeDemo.asm

That's the main program. It contains the data section and the code section. In the data section is a statement %include "dishArray.inc that instructs nasm to read this other file

dishArray.inc

This file contains the definition of the dish array, and of the constant N.

demo.asm

;;; ; demo.asm
;;; ; Authors: D. Thiebaut and CSC231 Class
;;; ;
;;; ; Demo program illustrating how to 
;;; ; use an include file to feed the dish
;;; ; array to the program.
;;; ;
;;; ; to assemble and run:
;;; ;
;;; ;     nasm -f elf -F  stabs demo.asm
;;; ;     ld -melf_i386 -o demo demo.o
;;; ;     ./demo
;;; ; -------------------------------------------------------------------


;;;  ------------------------------------------------------------
;;;  data areas
;;;  ------------------------------------------------------------

	        section .data
;;; the current dish with its cells.  We use 0 and 1 to
;;; indicate dead and live cells, respectively.
%include	"dishArray.inc"

;;; the new generation of cells.  That's the "future" of the
;;; cells in the dish.  We make it the same size as dish, and
;;; fill it with N dead cells.
	
newGen	        times   N db 0
	
;;; dishP is a string that will contain ' ' or '!' for
;;; each 0 or 1 in dish.  
dishP		times   N  db ' '
		db	10			; add a \n at the end
						;  of dishP
	
generation	dd	0			; save ecx from for generation loop
i		dd	0			; used by for loops
	
;;;  ------------------------------------------------------------
;;;  code area
;;;  ------------------------------------------------------------

	        section .text
	        global  _start

_start:
main:	
;;; -------------------------------------------------------------
;;; print( dish )
		;; first we copy dish into dishP and at the same
		;; time replace 0 by ' ' and 1 by '!'

;;; for i in range( N ):
		mov	esi, dish 
		mov	edi, dishP

		mov	dword[i], 0
forPrint:	cmp	dword[i], N
		jge	forPrintEnd
	
		mov	al, byte[esi]
		add	al, ' '			;0 becomes ' ', 1 becomes '!'
		mov	byte[edi], al
		inc	esi			;esi points to next byte in dish
		inc	edi			;edi points to next byte in dispP

		;; i++, loop back
		inc	dword[i]
		jmp	forPrint
forPrintEnd:	
	
		;; print dishP as a string.
		mov	eax, 4			;prints dishP to screen
		mov	ebx, 1
		mov	ecx, dishP 		;dishP address
		mov	edx, N+1		;+1 to include the \n
		int	0x80

	
;;;  exit()
exit:		mov     eax,1
	        mov     ebx,0
	        int     0x80	; final system call

dishArray.inc

padding0        db      0
dish            db      1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
                db      1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0
                db      0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1
N               equ     $-dish
padding1        db      0

maxGen          dd      10