CODE SEGEMENT
ASSUME CS:CODE
START: MOV AH,1
INT 21H ;等待键入字符,送AL
CMP AL,0DH ;是否是回车符？
JZ DONE ;是则转DONE退出程序
CMP AL,'0'
JB NEXT
CMP AL,'9'
JA CHARUP
MOV DL,AL
MOV AH,2
INT 21H
JMP START
CHARUP: CMP AL,41H
JB NEXT
CMP AL,5AH
JA CHRDN
DISPC: MOV DL,'C'
MOV AH,2
INT 21H
NEXT: JMP START
CHRDN: CMP AL,61H
JB NEXT
CMP AL,7AH
JA NEXT
JMP DISPC
DONE: MOV AH,4CH
INT 21H
CODE: ENDS
END START

我是新手 帮忙看看怎么回事 过不到编译