四（汇编程序设计）从键盘接收一个按键，如果按键是小写字母则输出“L”，如果按键是大写字母则输出“U”，如果按键是数字则输出“N”，如果不是以上字符，则输出“*”。

代码 

CSEG			SEGMENT
			ASSUME CS:CSEG
START:
			XOR AX,AX
			MOV AH,01H
			INT 21H

			CMP AL,30H
			JB OTHORS
			CMP AL,39H
			JA	CapitalLetter
			MOV DL,"N"
			MOV AH,02H
			INT 21H
			JMP OVER		
	
CapitalLetter:
			CMP AL,41H
			JB OTHORS
			CMP AL,5AH
			JA SmallLetter	
			MOV DL,"U"
			MOV AH,02H
			INT 21H 
			JMP OVER
SmallLetter:	
			CMP AL,61H
			JB OTHORS
			CMP AL,7AH
			JA OTHORS
			MOV DL,"L"
			MOV AH,02H
			INT 21H
			JMP OVER

OTHORS:
			MOV DL,"*"
			MOV AH,02H
			INT 21H

OVER:			MOV AX,4C00H
			INT 21H
CSEG ENDS
			END START