For the login part is good, everything works well on that part. But for registering a new account part, it keeps showing the invalid message although I full all the requirements which are username cant be repeated and the length of username should be more than 5 letters.

Here is my code

.MODEL SMALL
.STACK 64
.DATA
    welMsg DB "Welcome to Shopping Mall Company! ^_^"
    DB 13,10,"This is our company Loyalty Program System."
    DB 13,10,"Please login or register your account before proceeding to the next step.","$"
    
    ; indexing for usernames and passwords
    usersIndex dw usr1,usr2,usr3,usr4,usr5,usr6
    usr1 DB "siti02$"
    usr2 DB "joey02$"
    usr3 DB "robert$"
    usr4 DB 31 dup(?)
    usr5 DB 31 dup(?)
    usr6 DB 31 dup(?)
    userspasswordIndex dw usrpsw1,usrpsw2,usrpsw3,usrpsw4,usrpsw5,usrpsw6
    usrpsw1 DB "siti123456",'$'
    usrpsw2 DB "joey123456",'$'
    usrpsw3 DB "robert123",'$'
    usrpsw4 DB 31 dup(?)
    usrpsw5 DB 31 dup(?)
    usrpsw6 DB 31 dup(?)
    
    ;****************************** loginmessage for User Available or Not***********************
    loginmessage0 DB "************* Main Menu *************$"
    loginmessage1 DB "Enter 1 to Register a New Account$"
    loginmessage2 DB "Enter 2 to Login Account$"
    loginmessage4 DB "Choice: $"
    loginmessage5 DB "Invalid Choice, please select only 1 to 3 option$"
    loginmessageline DB "*************************************$"
    
    ;***********exitloginmessage*********
    exitloginmessage DB "Enter 3 for Exit$"

    ;****************************login loginmessage****************************
    totalUsr dw 3 ; store total available registered users
    IMSG DB "ACCESS DENIED$"
    VMSG DB "ACCESS GRANTED!$"
    
    ; ******************************loginmessage for User login*************************
    loginmessage6 DB "*******Login*********$"
    loginmessage7 DB "Enter username: $"
    loginmessage8 DB "Enter password: $"
    
    ; ***********************for register new account**********************************
    loginmessage9 DB "Set your user account(username): $"
    loginmessage10 DB "Set your password: $"
    
    ;***********************end message****************************
    endMsg DB 13,10,"Thanks for using Loyalty Program System.See you again! =)"
    DB 13,10," _ _ _ _ __ __ __ ___ __ __ __"
    DB 13,10,"|_ _ _ _| | | | | / __ \ | \ \ | | | | / / "
    DB 13,10," | | | |_| | | |__| | | \ \| | | |_/ / "
    DB 13,10," | | | _ | | __ | | |\ \ | | _ \ "
    DB 13,10," |_| |__| |__| |_| |_| |__| \___| |__| \___\ ","$"
    
    ;***********************input acc& pssw variable****************************
    regUser DB 31 dup(?)
    regPssw DB 31 dup(?)
    
    ;*****************************message for creating fail account**********************
    repeatAccMsg DB "Sorry the account has been used, Try other$"
    invalidLengthForUsername DB "Invalid username, Username Length must be greater than 5 characters$"
    invalidPassError DB "Sorry your password dose not fulfil, Password Length must be greater than 8 characters$"
    
    ;**************************login sucess & fail message*******************************
    invalidAccountInfo DB "Invalid Account Info, Username and password is not matched with database$"
    successfullLoginMsg DB "Your Account is Successfully login$"
    
    ;*************** message after register********************************
    confirmAccountMsg0 DB "By register this account,I agree to the terms and conditions$"
    confirmAccountMsg DB "Confirm to create the account(y/n): $"
    accountCreatedMsg DB "Account created!!!!$"
    accountFailCreatedMsg DB "Account create fail!$"
    databaseFullMsg DB "Sorry, database is Full, We can't create your account$"
.CODE

NEWLINE MACRO
  ;newline
 MOV AH,02H 
 MOV DL,0DH 
 INT 21H 
 MOV DL,0AH 
 INT 21H
ENDM

CLEARSCREEN MACRO
    MOV AX, 0600H
    MOV BH,71H
    MOV CX, 0000H 
    MOV DX,174FH
    INT 10H
ENDM

PRINTSTRING MACRO INPUT
 MOV AH, 09H
 LEA DX, INPUT
 INT 21H
ENDM

INPUTOPTION MACRO 
 MOV AH, 01H
 INT 21H
ENDM

STORING MACRO INPUT
    mov ah, 3Fh ; read an array of bytes from keyboard-0
    mov bx, 0 ; bx = 0 (select keyboard)
    mov cx, 30 ; cx = 30 (maximum bytes to read)
    lea dx, INPUT ; stored in DS:DX
    int 21h
ENDM

isValidAccountDetails proc
    lea si, usersIndex ; point to list of customername
    lea di, userspasswordIndex ; point to list of passwords
    mov cx, totalUsr
    checkUserAccount:
        push si ; push pointer of Username on stack
        push di ; push pointer of password on stack
        mov dx, [si] ; read one password from
        mov si, dx ; store address in si
        lea di, regUser ; store address of regUser in di
    checkNextChar:
        mov al, [si] ; read character of stored Username string
        mov bl, [di] ; read character of new Username string
        cmp al,bl ; compare chars, if not same
        JNE notMatch
        cmp al, '$' ; if same last character
        JE verifyPassword ; now verifyPassword
        inc si
        inc di
        JMP checkNextChar
    verifyPassword:
        pop si
        pop di
        mov dx, [si]
        mov si, dx ; di will contain actual correct password
        mov di, offset regPssw ; si will contain Agent typed password
    checkPsw:
        mov al,[si] ; read char from original psw string
        mov bl,[di] ; read char from new psw string
        cmp al,bl ; if chars are not same, then account information is invalid
        JNE wrongData
        cmp al,'$' ; if we reach last character '$'
        JE correctData ; then Agent account data is correct
        inc si
        inc di
        JMP checkPsw
    notMatch:
        pop di
        pop si
        add si, 2
        add di, 2
        loop checkUserAccount
    wrongData:
        mov ax, 0 ; store ax = 0 when wrong / invalid account information
        ret
    correctData:
        mov ax, 1 ; store ax = 1 when correct / valid account information
        ret
isValidAccountDetails endp


; this proc will check if the username is already registered or not
; if the username is already in used, then it will return ax = 0, otherwise ax = 1
isValidUserName proc
    mov cx, 0
    mov si, offset usersIndex
    checkUserExist:
        push si
        cmp cx, totalUsr
        JE validUserName
        mov dx, [si]
        mov si, dx
        mov di, offset regUser
        call isSameStrings
        cmp ax, 1
        JE invalidUserName
        pop si
        add si, 2
        inc cx
        JMP checkUserExist
    validUserName:
        pop si
        mov ax, 1
        ret
    invalidUserName:
        pop si
        mov ax, 0
        ret
isValidUserName endp

; this proc will check if two strings are same or not,
; string 1 is si, string 2 is di
isSameStrings proc
    ; si old string
    ; di new string
    checkSame:
        mov al,[si]
        mov bl,[di]
        cmp al,bl
        JNE notSame
        inc si
        inc di
        cmp al,'$'
        JNE checkSame
        mov ax, 1
        ret
        
    notSame:
        mov ax, 0
        ret
isSameStrings endp

createAccount proc
    ; get location of username for new available account
    lea si, usersIndex
    mov ax, totalUsr
    mov bl, 2 ;user address   totalUsr * 2 give me actual address for new usr
    mul bl
    add si, ax ; si will point to required address for username
    mov dx, [si]
    mov si, dx ; point to location of username
    lea di, regUser
    storeUser:
        mov al,[di]
        mov [si], al
        cmp al,'$'
        JE storePassword
        inc si
        inc di
        JMP storeUser
    storePassword: ; get location of password for new available account
        lea si, userspasswordindex
        mov ax, totalUsr
        mov bl, 2
        mul bl ;user address   totalUsr * 2 give me actual address for new usr
        add si, ax ; si will point to required address for password
        mov dx, [si]
        mov si, dx ; point to location of password
        lea di, regPssw
    storePsw: ; save password
        mov al,[di]
        mov [si], al
        cmp al,'$'
        JE accountCreated
        inc si
        inc di
        JMP storePsw
    accountCreated:
        add totalUsr,1 ; update total users
        ret
createAccount endp

; this proc store '$' symbol at the end of username string
placeEndSymbolForUser proc
    ; for username
    mov si, offset regUser
    readNextChar1:
    mov al,[si]
    cmp al,0DH
    JE storeEndSymbol1
    inc si
    JMP readNextChar1
    storeEndSymbol1:
    mov al,'$'
    mov [si], al
    ret
placeEndSymbolForUser endp
    
    
; this proc store '$' symbol at the end of user password string
placeEndSymbolForPsw proc
    ; for userPassword
    mov si, offset regPssw
    readNextChar2:
        mov al,[si]
        cmp al,0DH
        JE storeEndSymbol2
        inc si
        JMP readNextChar2
    storeEndSymbol2:
        mov al,'$'
        mov [si], al
        ret
placeEndSymbolForPsw endp

; this procedure will find the length of given string, which si register points
checkLength proc
    mov cx, 0 ; store length of string
    readNextChar3:
        mov al,[si]
        cmp al, '$'
        JE stopCheckLength
        inc si
        inc cx ; increment the length of string
        JMP readNextChar3
    stopCheckLength:
        ret 
checkLength endp




MAIN PROC 
    MOV AX,@DATA 
    MOV DS,AX 
    
    MOV AH, 0 ; set video mode
    MOV AL, 2 ; set row cols 80 x 26
    INT 10H
    
    CLEARSCREEN
    
    ;-----------DISPLAY WELCOME MESSAGE----------
    PRINTSTRING welMsg  
    newline
    
    
    ;--------------------------------------start of sign in sign up modulus----------------------
    ;---------display main menu and enter option----------
    loginmenu:
        newline
        PRINTSTRING loginmessage0
        newline
        PRINTSTRING loginmessage1
        newline
        PRINTSTRING loginmessage2
        newline
        PRINTSTRING exitloginmessage
        newline
        PRINTSTRING loginmessage4
        INPUTOPTION
    
    ;--------check entered option-----------------
    cmp al,'1'           ; if choice = '1' then create a new account
    JE oor1       
    cmp al,'2'            ; if '2' then login account
    JE oor2
    cmp al, '3'             ; if '3' then exit
    JE oor3
    newline
    ;------------validation error option-----------------
    PRINTSTRING loginmessage5    ;else print invalid message
    newline 
    jmp loginmenu
    
    oor1:
        jmp newuser
    oor2:
        jmp oldUser
    oor3:
        jmp exit
    
    
    
    ;------------------LOGIN OLD ACCOUNT---------------
    olduser:
        CLEARSCREEN
        NEWLINE
        PRINTSTRING loginmessage6       ;display "********login*********
        NEWLINE
        
        PRINTSTRING loginmessage7      ;display "Enter Username"
        
        ; read username from user through keyboard
        STORING regUser

        NEWLINE
        PRINTSTRING loginmessage8       ;display "Enter password"
        
        STORING regPssw
        
        ;place '$' at the end of username and password
        call placeEndSymbolForUser
        call placeEndSymbolForPsw
        
        ;--------------check username and passwords----------------
        CALL isValidAccountDetails
        cmp ax, 1
        JE loginSuccessfullyCustomer
        ;else
        PRINTSTRING invalidAccountInfo ;username and password is nto matched with database
        NEWLINE
        PRINTSTRING IMSG  ;DISPLAY "ACCESS DENIED'
        
    loginSuccessfullyCustomer:
        PRINTSTRING successfullLoginMsg
        NEWLINE
        PRINTSTRING VMSG ;DISPLAY "ACCESS GRANTED'
        NEWLINE
        CLEARSCREEN
        JMP mainmenu ;go to main menu 
        
    ;----------------Register new account------------------
    newuser:
        NEWLINE
        MOV AX, totalUsr
        cmp ax, 6       ;check if database whether is full or not(limit is 6)
        JNE createAcc   ; if it is not full, then create new account
        PRINTSTRING databaseFullMsg
        NEWLINE
        JMP mainmenu ;go to main menu 
        
    createAcc:
        PRINTSTRING loginmessage9 ; display "Set your user account(username): "
        STORING regUser 
        call placeEndSymbolForUser 
        
        call isValidUserName
        cmp aX, 1
        JNE oor4
        mov si, offset regUser
        call checkLength
        cmp cx, 5
        JBE oor5
        
        oor4:
            jmp invalidacc
        oor5:
            jmp invalidUserLength

    askPsw:
        PRINTSTRING loginmessage10 ; display "Set your password: "
        ;get password from user
        STORING regPssw
        call placeEndSymbolForPsw
        mov si, offset regPssw ; check password length
        call checkLength
        cmp cx, 8 ; if password length is <=8 then invalid password lengths
        JBE oor6
        ;else create user account
        ; createAccount
        NEWLINE
        PRINTSTRING confirmAccountMsg0 ; display "Confirm to create the account(y/n): "
        
        NEWLINE     
        PRINTSTRING confirmAccountMsg ; display "Confirm to create the account(y/n): "
        
        INPUTOPTION ; read character from keyboard      
        cmp al, 'y' ; check if al is equal 'y' or 'Y' is entered then create account
        JE yesCreateAccount
        cmp al,'Y'
        JE yesCreateAccount
        ; else account can't be created
        NEWLINE
        PRINTSTRING accountFailCreatedMsg ; display "Account create fail"
        NEWLINE
        JMP loginmenu ; goto main menu
        
        oor6:
            jmp invalidPswLength
        
    yesCreateAccount:
        call createAccount
        NEWLINE
        PRINTSTRING accountCreatedMsg
        
        NEWLINE
        mov ah,1
        int 21h
        JMP oldUser ; goto login
        
    invalidAcc:
        PRINTSTRING repeatAccMsg ; display "Sorry the account has been used, Try other"
        NEWLINE
        JMP createAcc ; ask again for username
        
    invalidUserLength:
        PRINTSTRING invalidLengthForUsername ; display "Invalid username, Username Length must be greater than 5 characters"
        NEWLINE
        JMP createAcc ; ask again for username
        
    invalidPswLength:
        PRINTSTRING invalidPassError ; display "Sorry your password dose not fulfil, Password Length must be greater than 8 characters"
        NEWLINE
        JMP askPsw ; ask again for user password

    exit:
        call end_prog
    end_prog:
        PRINTSTRING endMsg
        mov ah, 4ch
        int 21h
        ret
    ;--------------------------------end of sign in sign up modulus----------------------
    
    ;----------------------display main menu after login----------------
    mainmenu:
        PRINTSTRING welMsg ;temp msg
        
    MOV AX,4C00H 
    INT 21H
 
MAIN ENDP 
 END MAIN

Here is the problem that I facing now:

Although it's a bit long, I hope u guys can take time for looking at it. This is my assignment.

CodePudding user response：

An unfortunate fall-through problem

   call isValidUserName
   cmp aX, 1
   JNE oor4
   mov si, offset regUser
   call checkLength
   cmp cx, 5
   JBE oor5
                         <=== All is well: Need to jump to `askPsw` here
   oor4:
       jmp invalidacc
   oor5:
       jmp invalidUserLength

askPsw:

The code is missing a crucial jmp. For now the code falls through in oor4 eventhough the new username is long enough.

Next code solves the problem and avoids adding yet another jump to the program (mainly by inverting the condition):

    call isValidUserName     ; -> AX=[0=NOK, 1=OK]
    cmp  ax, 1
    JNE  oor4
    mov  si, offset regUser
    call checkLength         ; -> CX
    cmp  cx, 5
    JA   askPsw
  oor5:
    jmp  invalidUserLength
  oor4:
    jmp  invalidacc
     
askPsw: