两道道汇编题，刚学，高人们指点下吧

;字母必须是大写的哦
;1，编写十六进制数的乘法程序。要求从键盘上输入两个一位十六进制数据，
;乘积存入SUM单元。

DATAS SEGMENT
sum db ?
DATAS ENDS

CODES SEGMENT
ASSUME CS:CODES,DS:DATAS
START:
MOV AX,DATAS
MOV DS,AX
mov sum,0
call shuru
mov bl,al
call shuru
mul bl
mov sum,al
MOV AH,4CH
INT 21H
shuru proc near
a: mov ah,01h
int 21h
cmp al,30h
jb a
cmp al,3ah
jnb b
sub al,30h
jmp d
b: cmp al,41h
jb a
cmp al,47h
jnb a
sub al,37h
d: ret
shuru endp
CODES ENDS
END START
;字母必须是大写的哦,第二题
CRLF MACRO
MOV DL,0DH
MOV AH,02H
INT 21H
MOV DL,0AH
MOV AH,02H
INT 21H
ENDM
DATAS SEGMENT
sum db ?
x db 'shu ru x:$'
y db 'shu ru y:$'
DATAS ENDS

CODES SEGMENT
ASSUME CS:CODES,DS:DATAS
START:
MOV AX,DATAS
MOV DS,AX
mov sum,0
mov dx,offset x
mov ah,09h
int 21h
call shuru
mov bl,5
mul bl
mov bl,al
CRLF
mov dx,offset y
mov ah,09h
int 21h
call shuru
add al,bl
mov sum,al
MOV AH,4CH
INT 21H
shuru proc near
a: mov ah,01h
int 21h
cmp al,30h
jb a
cmp al,3ah
jnb b
sub al,30h
jmp d
b: cmp al,41h
jb a
cmp al,47h
jnb a
sub al,37h
d: ret
shuru endp
CODES ENDS
END START

嘿，我也正愁这两道题呢