Using the Amstrad CPC firmware:

org		$4000

txt_output:	equ	$bb5a

		push	hl
		ld	hl,world

print:		ld	a,(hl)
		cp	0
		jr	z,end
		call	txt_output
		inc	hl
		jr	print

end:		pop	hl
		ret

world:		defm	"Hello world!\r\n\0"