; ***********************************************************************
; *									*
; *	 Add Two Numbers (Version 4 of the Assembly Language Code)	*
; *									*
; ***********************************************************************

; Authors:  Saeid Nooshabadi and John Zaitseff
; Date:	    20th June, 2003
; Version:  1.5

; This simple program adds two integers together.  It first reads the
; values from memory into registers, adds the registers together, then
; stores the result back in memory.  This version uses the LDR = pseudo-
; instruction.


; -----------------------------------------------------------------------
; Assembly-language preamble for the main module

	.text				; Executable code follows

_start: .global _start			; "_start" is required by the linker
	.global main			; "main" is our main program

	b	main			; Start running the main program


; -----------------------------------------------------------------------
; Start of the main program

; This function performs the main work of the program, adding two integers
; originally stored in memory (in the variables "a" and "b") and storing
; the result back to memory (to the variable "c").

main:					; Entry to the function "main"

	ldr	r3, =a			; R3 = Address of "a"
	ldr	r1, [r3]		; R1 = 10 (from "a")

	ldr	r3, =b			; R3 = Address of "b"
	ldr	r2, [r3]		; R2 = 11 (from "b")

	add	r0, r1, r2		; R0 = a + b = 21

	ldr	r3, =c			; R3 = Address of "c"
	str	r0, [r3]		; Store the result to "c"

	mov	pc, lr			; Stop the program (return to the OS)

a:	.word	10			; Variable "a"
b:	.word	11			; Variable "b"
c:	.word	0			; Variable "c"

	.end