How to handle keyboard in real mode through BIOS interrupts?

assembly operating-system x86 calculator bootloader
narayanpatra picture narayanpatra · Nov 6, 2010 · Viewed 7.2k times · Source

I have to code for a operating system on which I can run a calculater.It is like a desktop calculater. For this I am reading the brokenthorn operating development series I have completed the second stage of bootloader The bootloader is in real mode. After this the author is explaining the protected mode. I don't want to use the protected mode. I don't have time for that. So I want to write the calculater in real mode by using bios interrupts. Is it possible? I think it can be written on the second stage of the bootloader(I am not sure.) Means I don't have to use a kernel(I am not sure). I don't know how to use BIOS interrupts to handle the keyboard. Can anybody provide me a link which will help me in this? And If anything wrong in whatevet I assumed above is wrong, please correct me.Thanks in advance.

Answer

Matthew Slattery picture Matthew Slattery · Nov 6, 2010

If you want to use high-level BIOS keyboard services, rather than handling the keyboard interrupts yourself, then INT 16h is what you want.

INT 16h with AH=00h or 10h will block waiting for a keypress (returns ASCII result in AL); use AH=01h or 11h to query whether a keypress is available first if you want to avoid blocking (returns immediately with ZF clear if a key is available, or set if not). See e.g. here, or here (or Google "INT 16h" for more).

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