.model small
.stack 1000h
.386

.data
    prompt db "Welcome to the Main Menu", 13, 10, "1. Adding 2 numbers", 13, 10, "2. Odd and Even", 13, 10, "3. Positive and Negative", 13, 10, "4. Exit", 13, 10,"Enter your choice: $"
    invalid db "Invalid choice. Please try again.$"
    newline db 13, 10, "$"
    msg1 DB 10,13,'Enter the first digit: $'
    msg2 DB 10,13,'Enter the second digit: $'
    msg3 DB 10,13,'The sum is: $'
    msg4 DB 10,13,'Enter first number: $'
    msg5 DB 10,13,'Enter second number: $'
    msg6 DB 10,13,'The results are: $'
    msg7 DB 10,13, "Enter a number (e.g., +5 or -3): $"
    positive_msg db 13, 10, "The number is positive.$"
    negative_msg db 13, 10, "The number is negative.$"
    zero_msg db 13, 10, "The number is zero.$"
    buffer db 255, "$" ; Buffer for user input
    even_msg db ' is even.$'
    odd_msg db ' is odd.$'
    x DB ?
    y DB ?
    sum DB ?

.code
start:
    ; Initialize data segment
    mov ax, @data
    mov ds, ax

display_menu:
    ; Display welcome message and menu
    mov ah, 09h
    lea dx, newline
    int 21h
    mov ah, 09h
    lea dx, prompt
    int 21h

read_choice:
    ; Read user input
    mov ah, 01h
    int 21h
    sub al, '0'  ; Convert ASCII digit to numeric value

    ; Check user's choice
    cmp al, 1
    je option1_selected
    cmp al, 2
    je option2_selected
    cmp al, 3
    je option3_selected
    cmp al, 4
    je exit_program
    
    jmp invalid_choice

option1_selected:
    ; Display message to enter first digit
    mov ah, 09h
    lea dx, msg1
    int 21h
    
    ; Read first digit
    mov ah, 01h
    int 21h
    sub al, '0'
    mov x, al
    
    ; Display message to enter second digit
    mov ah, 09h
    lea dx, msg2
    int 21h
    
    ; Read second digit
    mov ah, 01h
    int 21h
    sub al, '0'
    mov y, al
    
    ; Calculate sum
    mov al, x
    add al, y
    mov sum, al
    
    ; Display sum
    mov ah, 09h
    lea dx, msg3
    int 21h
    
    ; Display sum value
    mov dl, sum
    add dl, '0'
    mov ah, 02h
    int 21h
    jmp display_menu  ; Return to main menu

option2_selected:
    ; Display prompts for the numbers
    mov ah, 9
    lea dx, msg4
    int 21h

    ; Read the first number
    mov ah, 1
    int 21h
    mov bl, al ; Store the first number

    ; Display prompts for the numbers
    mov ah, 9
    lea dx, msg5
    int 21h

    ; Read the second number
    mov ah, 1
    int 21h
    mov cl, al ; Store the second number

    ; Display result message
    mov ah, 9
    lea dx, msg6
    int 21h

    ; Display the first number
    mov ah, 2
    mov dl, bl
    int 21h

    ; Display whether the first number is even or odd
    mov ah, 9
    mov al, bl
    test al, 1
    jz first_even
    lea dx, odd_msg
    int 21h
    jmp second_check

first_even:
    lea dx, even_msg
    int 21h

    ; Display the second number
second_check:
    mov ah, 2
    mov dl, cl
    int 21h

    ; Display whether the second number is even or odd
    mov ah, 9
    mov al, cl
    test al, 1
    jz second_even
    lea dx, odd_msg
    int 21h

second_even:
    lea dx, even_msg
    int 21h
    jmp display_menu  ; Return to main menu

option3_selected:
; Display input message
    mov ah, 09h
    lea dx, msg7
    int 21h

    ; Read user input as a string
    mov ah, 0Ah
    lea dx, buffer
    int 21h

    ; Check if the input is positive, negative, or zero
    mov si, offset buffer + 2  ; Point SI to the beginning of the input string
    mov al, [si]               ; Load the first character of the input
    cmp al, '+'                ; Check if it's a positive sign
    je positive_number
    cmp al, '-'                ; Check if it's a negative sign
    je negative_number
    cmp al, '0'                ; Check if it's '0'
    je zero_number
    jmp invalid_number

positive_number:
    ; Display positive message
    mov ah, 09h
    lea dx, positive_msg
    int 21h
    jmp display_menu

negative_number:
    ; Display negative message
    mov ah, 09h
    lea dx, negative_msg
    int 21h
    jmp display_menu

zero_number:
    ; Display zero message
    mov ah, 09h
    lea dx, zero_msg
    int 21h
    jmp display_menu  ; Return to main menu

invalid_number:
    ; Display invalid number message
    mov ah, 09h
    lea dx, newline
    int 21h
    mov ah, 09h
    lea dx, invalid
    int 21h
    jmp display_menu  ; Return to main menu

exit_program:
    ; Display newline and exit
    mov ah, 09h
    lea dx, newline
    int 21h

    ; Terminate program
    mov ah, 4Ch
    int 21h

invalid_choice:
    ; Display invalid choice message
    mov ah, 09h
    lea dx, newline
    int 21h 
    mov ah, 09h
    lea dx, invalid
    int 21h
    jmp display_menu  ; Restart the main menu

end start

I have a code here that runs fine. The only issue I’m facing is how to input more than one digit and also display the results properly. For example, if I input 9 + 10, the sum should be 19. Similarly, if I input 12 and 15, the output should be “12 is even. 15 is odd” (vice versa). Additionally, in option 3, how can I fix my code so that I can display two different numbers that is in positive and negative and also it will results if the number is positive or negative. Moreover,if I input to all options a symbols or letters, it should display “invalid”.