8086 32 bit integer input

;A procedure that sums BX-AX and DX-CX
	;the result is returned in BX-AX
	longadd proc
		add ax,cx
		adc bx,dx
		ret
	longadd endp



;reads a number and place on dx:ax
	readn proc near
	push cx
	push bx  ; saving the other registers
	push bp
	mov bp , 0
	mov cx , 10    ; make cx 10 
	mov bx , 0     ;set to 0
	mov dx , 0     ; set to 0
	readn1:               
		mov ah , 1             ;make ah 1 in order to call interrup of one char with echo
		int 21h		       ;activate the interrupt
		cmp al , 13d
		je readn2
		cmp al , '0'           ;if its < 0 ends the loop
		jb set0
		cmp al , '9'
		ja set0			; if its >9 ends the loop
		sub al , '0' 		; turn the char into decimal
		push ax			;saves ax
		mov ax ,dx		;places the value from dx into ax for mult
		mul cx			; mult by 10
		mov dx ,ax		;restore dx mult by 10		
		mov ax ,bx		;makes ax bx for mult
		mul cx			;mult by 10
		mov bx ,ax		;restore bx mult by 10
		pop ax			; restore ax to value before mult
		mov ah , 0		;makes ah 0
		push ax			;saves variables
		push cx			;set stuff for long adding
		mov cx , ax
		mov ax , bx
		mov bx , dx
		mov dx , 0
		call longadd		; long add happens
		mov dx ,bx
		mov bx , ax
		pop cx
		pop ax
		jmp readn1 ; goes back to start of the loop
	set0:
		mov bp , 1	; uses bp to hold a flag for when ilegal input occurs
		jmp readn1
	set02:
		xor dx ,dx	;makes them 0 due to ilegal input
		xor ax ,ax
		mov bp , 0
	readn2:			;checks if it there was an error and gives output
		mov ax,bx
		cmp bp ,1
		je set02
	tend1:			;returns variables
		pop bp
		pop bx
		pop cx
		ret		;ends proc
 	readn endp