Unexpected Output When Using 16-bit Assembly with DOS Interrupts for File I/O
I've been banging my head against this for hours. I'm trying to configure I'm converting an old project and I'm having trouble with a simple assembly program that reads a text file using DOS interrupts... I'm working with the NASM assembler and targeting a 16-bit real mode environment. The code compiles without any errors, but when I try to read the content of the file, the output is not what I expect. The file is supposed to contain a few lines of text, but I only get a single character or sometimes the program hangs completely. I've set up the file descriptor correctly and am using interrupt 21h with function 3Dh to open the file, but when I try to read from it using 3Fh, the output is inconsistent. Here’s a snippet of the code I’m using: ```asm section .data filename db 'myfile.txt', 0 buffer db 100 dup(0) handle db 0 bytesRead db 0 section .text global _start _start: ; Open file mov ah, 3Dh mov al, 0 ; read-only lea dx, [filename] int 21h jc .behavior mov [handle], al ; Read file mov ah, 3Fh mov bx, [handle] lea dx, [buffer] mov cx, 100 int 21h jc .behavior ; Output read data ; (Assuming we will handle output somewhere here) ; Close file ; (Close code here) jmp .done .behavior: ; Handle errors (could log or print behavior) .done: ; Exit program int 20h ``` I've tried adjusting the buffer size and ensuring the file exists in the current directory, but the scenario continues. I also made sure the file is not empty. When I check the value of `AL` after the `3Fh` call, it holds a number less than 100, indicating that fewer bytes were read than expected, which further confuses me since I need to figure out why. Any insights or suggestions on how to properly read from the file or debug this scenario would be greatly appreciated. This is my first time working with Assembly LTS. Thanks for taking the time to read this! This is for a application running on Debian. Has anyone dealt with something similar? Cheers for any assistance!