05_05.asm

清华大学计算机系汇编语言课程

;05_05.asm
;Created by RunningOn Chen.
;2003011434 J34 CS dept, THU
;2005-11-14


data segment
	message db 'Input the number of beeps:$'
	error_msg db 0dh, 0ah, 'Invalid number.', 0dh, 0ah, '$'
	newline	db 0dh, 0ah, '$'
data ends

code segment
main	proc far
	assume ds:data, cs:code
start:
	mov	ax, data
	mov	ds, ax

	mov	dx, offset message
	mov	ah, 09h
	int	21h		;output string

	mov	ah, 01h
	int	21h		;wait for input

	cmp	al, '0'
	jb	error
	cmp	al, '9'
	ja	error
	sub	al, '0'

	mov	cl, al		;cx = al
	mov	ch, 0h

cycle:
	mov	dl, 07h		;sound a beep
	mov	ah, 02h
	int	21h		;output a char

	push	cx		;pause for a while
	mov	cx, 0ffffh
pause:	mov	bx, 01500h
pause2:	dec	bx
	jnz	pause2

	loop	pause
	pop	cx

	loop	cycle		;loop

	mov	dx, offset newline
	mov	ah, 09h
	int	21h		;enter a new line
	
	jmp	exit

error:
	mov	dx, offset error_msg
	mov	ah, 09h
	int	21h		;output error_msg

exit:
	mov	ax,4c00h
	int	21h		;exit

main	endp
code	ends
	end start