Nanjing University of Posts and Telecommunications Assembly Language Programming Experiment II (Design of User Login Verification Program)

1. Experimental purpose and requirements

1. Master the writing of cycle programs and the method of ending the cycle.
2. Master the usage of DOS and BIOS function calls.

2. Experimental content

After the implementation program of the user login verification program is executed, a prompt operation is given, asking the user to type in the user name and password; when the user types in the password, the program does not echo the typed characters; only when the user typed in the user name, password string and the program default When the character strings are the same, the welcome interface is displayed and DOS is returned; otherwise, a prompt message is given, and the user name or password is wrong, and input again. Interface color customization (color or black and white)

3. Experimental environment (experimental equipment)

XP/WIN7+MASM/TASM/Easy Assembly/Future Assembly

4. Experiment code

      .586
DATA  		SEGMENT 	USE16
	MESG1 		DB 		'INPUT YOUR USERNAME: $'		;提示字符
	MESG2  		DB 		'INPUT YOUR PASSWORD: $' 
	ERROR  		DB 	'-----USERNAME OR PASSWORD ERROR!----$'
	WELCOME 	DB 	'---------------WELCOME!-------------$'		
	
	
	_USERNAME  	DB 		'root'
	_PASSWORD  	DB 		'root'
	_ULEN  		EQU 	$-_USERNAME         ; 用户名长度
	_PLEN  		EQU 	$-_PASSWORD       	; 密码长度
	
	USERNAME  	DB		15   				; 输入的用户名
	PASSWORD  	DB 		15 DUP(?)          	; 输入的密码
	PLEN  		DB 		0                  	; 输入密码的长度
	
	
DATA  		ENDS


CODE  		SEGMENT 	USE16
      	ASSUME 	CS: CODE, DS: DATA
BEG:  	MOV 	AX, 	DATA
      	MOV 	DS, 	AX
NEXT0:  MOV 	AH, 	9    			;09H功能号，显示DS：DL内字符串
      	MOV 	DX, 	OFFSET MESG1
      	INT 	21H
      	MOV 	AH, 	0AH   			;键盘输入字符串并显示，存在U缓冲区
		MOV 	DX, 	OFFSET USERNAME  		;用户输入字符串起始偏移位置放入DX缓冲区
      	INT 	21H
      	MOV 	AH, 	2
      	MOV 	DL, 	0AH            	;换行字符
      	INT 	21H
      	MOV 	AH, 	9             	;显示提示字符串
      	MOV 	DX, 	OFFSET MESG2
      	INT 	21H
      	MOV 	CX, 	_PLEN
      	MOV 	SI, 	OFFSET PASSWORD  	;把输入密码起始偏移地址放入SI
NEXT1:  MOV 	AH, 	07H         	;无回显从键盘读入一个字符
      	INT 	21H
      	CMP 	AL, 	0DH          	;判断输入是否结束
      	JE 	IND
      	MOV 	[SI], 	AL       		;将输入密码字符放入数据区：PWD
      	MOV 	AH, 2          			;每输入一位密码显示一个‘*’
      	MOV 	DL, '*'
      	INT 	21H
      	INC 	PLEN
      	INC 	SI
      	JMP 	NEXT1
IND:  	MOV 	AH, 	2             	;输出换行
      	MOV 	DL, 	0AH
      	INT 	21H
     	MOV 	BX, 	OFFSET USERNAME+1    	;[BX]=实际输入字符数
      	MOV 	AL, 	[BX]
      	CMP 	AL, 	_ULEN          	;比较用户名长度    
      	MOV   BX, 	OFFSET _USERNAME
      	MOV 	SI, 	OFFSET _USERNAME+2
      	MOV 	CX, 	_ULEN          	;设置循环次数
NEXT2:  MOV 	AL, 	[BX]
      	CMP 	[SI], 	AL          	;循环比较用户名是否正确
      	INC   	SI
      	INC 	BX
      	LOOP 	NEXT2
      	MOV 	BX, 	OFFSET _PASSWORD
      	MOV 	SI, 	OFFSET PASSWORD
      	MOV 	CL, 	PLEN
      	MOV 	CH, 	0
      	CMP 	CX, 	_PLEN          	;比较密码长度
      	JNZ 	ERR
      	MOV 	CX, 	_PLEN
NEXT3:  MOV 	AL, 	[BX]
      	CMP 	[SI], 	AL          	;循环比较密码字符是否正确
      	JNZ 	ERR
      	INC 	SI
      	INC 	BX
      	LOOP 	NEXT3
      	JMP 	WEL
ERR:  	MOV 	AH, 	9
      	MOV 	DX, 	OFFSET ERROR 	;输出用户名或密码错误提示
      	INT 	21H
      	MOV 	AH, 	2
      	MOV 	DL, 	0AH
		INT 	21H
      	JMP 	NEXT0
WEL:  	MOV 	AH, 	9             	;输出登录成功的提示
      	MOV 	DX, 	OFFSET WELCOME
      	INT 	21H
      	JMP 	EXIT
EXIT:  	MOV 	AH, 	4CH
      	INT 	21H
CODE  	ENDS
      	END BEG

5. Experimental process description and result analysis

1. After the program is executed, a prompt operation is given, and the user is asked to enter the user name and password.
2. When the user types in the password, the program will not echo the typed characters; only when the user name and password string typed by the user are the same as the default string in the program, the welcome interface will be displayed and DOS will be returned; 3. Otherwise, a prompt message will be given
. Username or password is wrong, please enter again.

6. Experimental summary (including problems and solutions, experience, opinions and suggestions, etc.)

1. Pay attention to the use of sub-function calling methods
2. The naming format of variables should be unified and concise
3. The use of program counter CX