BCD HEX ass 4

section .data
ano     db 10, "Assignment No.:4",                              10
        db 10, "-------------------------------------------",   10
        db 10, "Conversion of Hex to BCD and BCD to Hex",       10
        db 10, "-------------------------------------------",   10

ano_len    equ   $- ano

menu    db 10, "1) HEX to BCD", 10
        db 10, "2) BCD to HEX", 10
        db 10, "3) Exit",       10
        db 10, "Enter your choice:"

menu_len equ  $- menu

hmsg    db 10, "Enter 4 digit Hex number:", 10
hmsg_len   equ  $- hmsg

ebmsg   db 10, "The equivalent BCD number is:", 10
ebmsg_len  equ  $- ebmsg

bmsg    db 10, "Enter 5 digit BCD number:", 10
bmsg_len   equ  $- bmsg

ehmsg   db 10, "The equivalent Hex number is:", 10
ehmsg_len  equ  $- ehmsg

emsg   db 10, "Invalid Input!", 10
emsg_len   equ  $- emsg

%macro Print 2
    mov rax, 1
    mov rdi, 1
    mov rsi, %1
    mov rdx, %2
    syscall
%endmacro

%macro Read 2
    mov rax, 0
    mov rdi, 0
    mov rsi, %1
    mov rdx, %2
    syscall
%endmacro

%macro Exit 0
    mov rax, 60
    mov rdi, 0
    syscall
%endmacro
;---------------------------------------------------------------
section .bss
    buf resB 6
    char_ans resB 4
    ans resB 12
;---------------------------------------------------------------
section .text
    global _start
_start:

    Print ano, ano_len
MENU:
    Print   menu, menu_len
    Read    buf, 2                  ;accept choice i.e. 1 digit + enter

    mov     al, [buf]               ;contains only digits character
c1:
    cmp al, '1'
    jne c2
    Print hmsg, hmsg_len
    Print ebmsg, ebmsg_len
    jmp MENU
c2:
    cmp al, '2'
    jne c3
    Print bmsg, bmsg_len
    Print ehmsg, ehmsg_len
    jmp MENU
c3:
    cmp al, '3'
    jne invalid
    Exit

invalid:
    Print emsg, emsg_len
    jmp MENU

Exit
;-------------------------------------------------------
BCD_HEX:
    Print bmsg, bmsg_len
    Read buf, 6                 ;5 digit + 1 Enter

    mov rsi, buf                ; points start of buffer
    xor ax, ax                  ; previous digit = 0
    mov rbp, 5                  ; counter
    mov rbx, 10                 ; multiplier

next:
    xor cx, cx                  ; contains next digit each time
    mul bx                      ; (ax*bx) + cl
    mov cl, [rsi]
    sub cl, 30h
    add ax, cx

    inc rsi                     ; point at the next digit
    dec rbp
    jnz next

    mov [ans], ax               ; store ax in ans because ax get change in Print Macro
    Print ehmsg, ehmsg_len

    mov ax, [ans]
    call Disp_16                ; Print hex number

RET
;-------------------------------------------------------
Disp_16:
    MOV RSI, char_ans + 3
    MOV RCX, 4
    MOV RBX, 10

next_digit:
    mov rdx, 0
    div rbx
    cmp dl, 9
    jbe add30
    add dl, 07h

add30:
    add dl, 30h

    mov [rsi], dl
    dec rsi
    dec rcx
    jnz next

Print char_ans, 4
RET
;--------------------------------------------------------