ASM Program to comvert BCD to HEX [MP Part2]

Problem Statement Part 2: 

Write X86/64 ALP to convert 4 - digit Hex number into its equivalent BCD number and 5 - digit BCD n umber into its equivalent HEX number. Make your program user friendly to accept the choice from user for:
(a) HEX to BCD
b) BCD to HEX
 (c) EXIT. Display proper strings to prompt the user while accepting the input and displaying the result. (wherever necess ary, use 64 - bit registers)

Code:- 

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%macro scall 4 ;macro to take input and output mov rax,%1 mov rdi,%2 mov rsi,%3 mov rdx,%4 syscall %endmacro Section .data msg1:db "Enter 5 Digit BCD Number: ",0x0A len1: equ $-msg1 msg2: db "Hex Number: ",0x0A len2:equ $-msg2 cnt :db 00H cnt2:db 00H Section .bss num:resb 6 ans: resb 4 result:resb 8 Section .text global main main: scall 1,1,msg1,len1 scall 0,0,num,6 mov rsi,num call AtoH mov edx,ebx ;copy conveted number to edx MOV eax,00H mov ebx,00H mov al,dl AND AL,0FH mov Bl,01H MUL Bl ADD dword[ans],eax ROR EDX,4 MOV EAX,00H mov ebx,00H MOV AL,DL AND AL,0FH MOV BL,0AH MUL BL ADD DWORD[ans],EAX ROR EDX,4 MOV EAX,00H mov ebx,00H MOV AL,DL AND AL,0FH MOV BL,64H MUL BL ADD DWORD[ans],EAX ROR EDX,4 MOV EAX,00H mov ebx,00H MOV AL,DL AND AL,0FH MOV BX,03E8H MUL BX ADD DWORD[ans], EAX ROR EDX,4 MOV EAX,00H mov ebx,00H MOV AL,DL AND AL,0FH MOV BX,2710H ;FIFTH DIGIT (100000 dECIMAL) MUL BX ADD DWORD[ans],EAX MOV EDX, DWORD[ans] MOV RDI,result call HtoA scall 1,1,msg2,len2 scall 1,1,result,8 mov rax,60 mov rdi,0 syscall AtoH: ;result hex no is in ebx mov byte[cnt],05H mov ebx,00H hup: rol ebx,04 mov al,byte[rsi] cmp al,39H JBE HNEXT SUB al,07H HNEXT: sub al,30H add bl,al INC rsi DEC byte[cnt] JNZ hup ret HtoA: ;hex_no to be converted is in dx //result is stored in rdi/user defined variable mov byte[cnt2],08H aup: rol EDX,04 mov cl,dl and cl,0FH CMP CL,09H jbe ANEXT ADD cl,07H ANEXT: add cl, 30H mov byte[rdi],cl INC rdi dec byte[cnt2] JNZ aup ret

Output: