Tiny Assembly program

tiny_program.s

@ This program counts all the even numbers cointained in the range from 0 to 10
@ in reverse order, this is: 10 + 8 + 6 + 4 + 2 = 30

			
	@ Constants definition.
	.equ	STACK_TOP, 0x20000800
	.text
	@ The symbol _start is required by the GNU Linker to specify
	@ the first instruction to be executed in a program.
	.global	_start
	.code	16		@ Indicates the program code is in Thumb.
	.syntax unified		@ Indicates that the unified assembly
				@ language syntax is used.

_start:
	.word	STACK_TOP, main
	.type	main, function @Declares that the symbol main is a function.

main:	@ Start of main program.
	@ Initialize registers.
	mov	r0, #10		@ Starting loop counter value.
	mov	r1, #0		@ Starting result.
	@ Calculated 10+8+6+4+2.

loop:
	add	r1, r0		@ R1 = R1 + R0
	subs	r0, #2		@ Decrement R0, update flag ('S' suffix).
	bne	loop		@ If result not zero jump to loop.
	@ Result is now in R1

deadloop:
	b	deadloop	@ Infinite loop.
	.end			@ End of file.