最近在学习汇编，练习编写文件复制的程序，在运行程序的时候到遇到询问是否覆盖时往里输入就不行了，按键盘还噔噔噔的响，这是为什么TAT
源代码如下：
DATA SEGMENT
MSOURCE DB "Please input the path and the source file(***::::.***):",13,10,"$"
MGOAL DB "Please input the path abd the goal file(***:***.***):",13,10,"$"
FERR DB "Cannot open the file currectly!",13,10,"$"
FOK DB "File Open Successed",13,10,"$"
CREERR DB "Cannot creat the file!",13,10,"$"
CROK DB "Creat File Successed!",13,10,"$"
RERR DB "Reading Error!",13,10,"$"
WERR DB "Writing Error!",13,10,"$"
CPS DB "Copy Success!",13,10,"$"
FEX DB "The File has already existed!Are you sure to cover it?(y/n)",13,10,"$" ;y 6E 0110 1111 n 64 0110 0100
NC DB "Copy Stopped!",13,10,"$"
JUG DB 1
DB 0
DB 2 DUP(0) ;判断输入为y还是n
SFNUM DW 0 ;待存源文件号
GFNUM DW 0 ;待存目标文件号
ENUM DW 0 ;待存覆盖文件号
BUFFLEN=50
BUFFER DB BUFFLEN
DB ?
DB BUFFLEN DUP(0)
DATA ENDS
CODE SEGMENT
ASSUME DS:DATA,CS:CODE
START:
MOV AX,DATA
MOV DS,AX
LEA DX,MSOURCE
CALL PRINT ;提示输入源文件路径
MOV DX,OFFSET BUFFER
MOV AH,0AH
INT 21H ;输入源文件路径
LEA SI,BUFFER
MOV AL,[SI+1]
XOR AH,AH
ADD SI,2
ADD SI,AX
MOV BYTE PTR[SI],0 ;将输入文件名的最后一个回车符换成0
MOV DX,OFFSET BUFFER+2
MOV AH,3DH
INT 21H ;打开源文件
JNC OPENOK ;打开成功跳至OPENOK
JC FRJ ;若打开出错，CF进位，跳至FERROR提示出错
OPENOK:
MOV SFNUM,AX ;将源文件号存入SFNUM
MOV DX,OFFSET FOK
CALL PRINT ;提示源文件打开成功
MOV DX,OFFSET MGOAL
CALL PRINT ;提示输入目的路径
MOV DX,OFFSET BUFFER
MOV AH,0AH
INT 21H ;输入目的路径
LEA SI,BUFFER
MOV AL,[SI+1]
XOR AH,AH
ADD SI,2
ADD SI,AX
MOV BYTE PTR[SI],0
MOV DX,OFFSET BUFFER+2
MOV AH,3DH
INT 21H ;查看目的路径中是否已有可打开的该文件
JNC EXIST
JC NOTEXIST ;如果不存在直接创建
EXIST:
MOV ENUM,AX
MOV BX,ENUM
MOV AH,3EH
INT 21H ;关闭待覆盖文件
LEA DX,FEX
CALL PRINT
MOV DX,OFFSET JUG
MOV AH,0AH
INT 21H
LEA SI,JUG
MOV AL,[SI+1]
XOR AH,AH
ADD SI,2
ADD SI,AX
MOV BYTE PTR[SI],0
MOV AL,JUG+2
AND AL,1
MOV AH,AL
SAHF
JC DEL ;若输入为y则跳至DEL先删除
FRJ:JC FERROR
LEA DX,NC
CALL PRINT
JMP START
DEL:
MOV DX,OFFSET BUFFER+2
MOV AH,41H
INT 21H ;删除已存在文件
NOTEXIST:
MOV DX,OFFSET BUFFER+2
MOV CX,0
MOV AH,3CH
INT 21H ;在目标路径建立文件
JNC CREOK ;若创建成功跳至CREOK
JC CREERROR ;若创建出错，CF进位，跳至CREERROR关闭文件并提示出错
CREOK:
MOV GFNUM,AX ;将目的文件号存入GFNUM
LEA DX,CROK
CALL PRINT
COPY_CONT:
MOV DX,OFFSET BUFFER
MOV CX,BUFFLEN
MOV BX,SFNUM
MOV AH,3FH
INT 21H ;读源文件
JC RERROR ;若读文件出错，跳至RERROR提示读文件出错
OR AX,AX ;循环相或直至已到文件尾，进位标志CF清零
JZ COPYOK ;复制完成，循环结束
MOV CX,AX ;写入的字节数录入
MOV BX,GFNUM ;目的文件号录入
MOV AH,40H
INT 21H ;写文件
JC WERROR ;若写文件出错，跳至WERROR提示写文件出错
JMP COPY_CONT ;继续循环
FERROR:
LEA DX,FERR
CALL PRINT
JMP EXIT
CREERROR:
MOV BX,SFNUM
MOV AH,3EH
INT 21H ;关闭源文件
LEA DX,CREERR
CALL PRINT
JMP EXIT
WERROR:
LEA DX,WERR
CALL PRINT
JMP EXIT
RERROR:
LEA DX,RERR
CALL PRINT
JMP EXIT
PRINT PROC NEAR
MOV AH,09H
INT 21H
RET
PRINT ENDP
COPYOK:
MOV BX,SFNUM
MOV AH,3EH
INT 21H ;关闭源文件
MOV BX,GFNUM
MOV AH,3EH
INT 21H ;关闭目标文件
LEA DX,CPS
CALL PRINT
EXIT:
MOV AX,4C00H
INT 21H
CODE ENDS
END START
如图，到这一步就输不进去了，求指点QAQ
