I'm currently making a NASM 8086 program that Encrypts and Decrypts a message, and was wondering if I can get some help on fixing my code so that it would be a fully functional program without any error. This is what I have so far.

; read a string ; encrypt it, and decrypt it.

org 100h

section .data ;___________________________DATA prompt1: db "What is your secret message? $" prompt2: db "The encrypted message is: $" prompt3: db "The message after decryption is: $" testout: db "*************** $"

key db 0Fh ; encryption key* CRLF db 13, 10, '$' ; carriage return line feed NULL db 0 ; null character

section .bss ; bss section* buffer resb 80 ; 80 reserve bytes*

section .text

;_____________________________SCREEN TEXT mov ah, 9 ; Used to print text stored in prompt1 mov dx, prompt1 ; int 21h ; end text output

;_______________________INSTRING (KEYBOARD INPUT) instring: mov cx, 0 ; CX counts characters starts at 0

cld ; process string left to right* mov di, buffer ; move buffer into data index*

mov ah, 1 ; read character from standard input* int 21h ; read character* while1: cmp al, 13 ; is character carriage return* je endwhile1 ; if carriage return exit loop* inc cx ; increment cx* stosb ; store character just read into buffer* int 21h ; read next character* jmp while1 ; loop until all characters read* endwhile1: ; endwhile1 (end of loop)* mov byte [di], NULL ; store ASCII null character (end of array)* mov dx, buffer ; dx is the address arg to print*?

;__________________________PRINT TO SCREEN lp:

cld ; process string left to right* lodsb mov dl, al mov ah, 2 int 21h loop lp

;___________________________CODER (encode data) ; mov si,0 ; string index register(si = string index)*** while1: cmp byte [si+msg],'$' ; looks for "$" to end loop*** je endwhile1 ; "$" ends loop*** mov al,[si+msg] ; moving through msg one character at a time*** xor al,[key] ; XOR value stored in al (encode)*** mov [si+coded],al ; move encoded character to al*** inc si ; increment si (array index counter)*** jmp while1 ; endwhile1: mov byte [si+coded],'$' mov ah,9 ; write string to standard output *** mov dx,coded ; store coded in output register *** int 21h ; output coded *** mov si,0 while2: cmp byte [si+coded],'$' je endwhile2 mov al,[si+coded] xor al,[key] mov [si+decoded],al inc si jmp while2 endwhile2: mov byte [si+decoded],'$' mov ah,2 ; write characer to standard output*** mov dl,13 ; store carrage carriage return code*** int 21h ; output carriage return*** mov dl,10 ; line feed code*** int 21h ; output line feed*** mov ah,9 ; write string to standard output *** mov dx,decoded ; store decoded in output register *** int 21h ; output decoded ***

exit: mov ah, 04Ch ; DOS function: Exit program mov al, 0 ; Returns exit code value int 21h ; Call DOS (Terminate Program) CODER: cmp al, NULL ;if the character is null, we're done je CODER xor buffer, 0Fh lodsb ;read next character jmp CODER ;loop until done