Question

The program needs to take in a simple string from the user and display it back. I have gotten the program to take input from the user but I can’t seem to store it. Here is what I have so far:

BITS 32 global _main section .data  prompt db 'Enter a string: ', 13, 10, '$' input resd 1 ; something I can using to store the users input.  name db 'Name: ******', 13, 10,'$' StudentID db '********', 13, 10, '$' InBoxID db '*************', 13, 10, '$' Assignment db '************', 13, 10, '$' version db '***************', 13, 10, '$'  section .text _main:  mov ah, 9 mov edx, prompt int 21h mov ah, 08h while:     int 21h             ; some code that should store the input.     mov [input], al     cmp al, 13     jz endwhile     jmp while endwhile:  mov ah, 9     ; displaying the input.  mov edx, name int 21h mov edx, StudentID int 21h mov edx, InBoxID int 21h mov edx, Assignment int 21h mov edx, version int 21h ret 

I am assembling this using NASM.

Answer 1

You’re only reading the characters without storing them. Instead of storing into that ‘input’, you should store AL either directly into StudentID/InBoxID/Assignment/Version. You could take advantage of their relative positions in memory and write a single loop to fill all of them, as in a contiguous space.

It could go like this:

; For each string already padded with 13, 10, $ ; at the end, use the following: mov ah, 08h mov edi, string mov ecx, max_chars cld while:         int 21h         stosb         ; store the character and increment edi         cmp ecx, 1    ; have we exhausted the space?         jz out         dec ecx         cmp al, 13         jz terminate  ; pad the end         jmp while terminate:         mov al, 10         stosb         mov al, '$'         stosb out:         ; you can ret here if you wish 

I didn’t test, so it might have mistakes in it.

Or you could use other DOS functions, specifically INT21h/0Ah. It could be more optimal and/or easier.