ASM help.

[Ike]

OK, so i need to write a program that lets a user input text with is then encrypted, displayed on the screen and store in the buffer. Then i need to save the encrypted text into a file which is where I'm stuck. I can kinda do it but it saves a load of other stuff I don't want and I have no idea what to do.

 

This is my code so far in the attachment.