用汇编语言编写程序 ：从键盘接收一个小写字母，然后找到它的前导字符和后续字符，再按顺序显示这三个字符

DATA SEGMENT
A DB ?
B DB ?
C DB ?
DATA ENDS

STACKE SEGMENT STACK
DW 1024 DUP(?)
STACKE ENDS

CODE SEGMENT
ASSUME CS:CODE,DS:DATA,SS:STACKE
START:
MOV AX,DATA
MOV DS,AX

MOV AH,1
INT 21H
SUB AL,30H
MOV B,AL
ADD AL,30H
ADD AL,1
SUB AL,30H
MOV C,AL
ADD AL,30H
SUB AL,2
SUB AL,30H
MOV A,AL

MOV DL,0DH
MOV AH,2
INT 21H
MOV DL,0AH