DOS ain't dead

MODE command (Developers)

posted by bretjohn  , Rio Rancho, NM, 16.10.2021, 00:50

> MODE can do an OS call and the OS can keep
> track of the situation. I assumed that is
> how it was done in MSDOS too, but maybe not.

I'm not sure how MS or Free or any other DOS actually does it. But I think if I were implementing it I would just read the UART data directly from the I/O port. Even though there's not a standard BIOS (INT 14h) call you can use, the base I/O addresses of the four serial ports are stored in the BIOS Data Area (BDA) at 0040:0000 so they are part of the BIOS. It odes seem weird that there isn't an INT 14h call to read the current status, almost as if they expect you to use direct I/O.

I've only messed around with serial ports a little bit, and when I did I always used direct I/O. I wrote a TSR called SERIAL that monitors the status of a serial port in "real time" on the screen, which you can download from my website (bretjohnson.us) if you're interested. I also know in the old days at least some of the BBS's used FOSSIL, which is an "upgraded" INT 14h, but that won't help you here.

Complete thread:

• MODE command - kerravon, 14.10.2021, 12:34
  • MODE command - bretjohn, 14.10.2021, 17:36
    • MODE command - kerravon, 15.10.2021, 00:29
      • MODE command - bretjohn, 15.10.2021, 07:29
        • MODE command - kerravon, 15.10.2021, 07:42
          • MODE command - bretjohn, 16.10.2021, 00:50
            • MODE command - kerravon, 16.10.2021, 02:07
              • MODE command - RayeR, 18.10.2021, 21:44
  • MODE command - DosWorld, 22.10.2021, 03:35
    • MODE command - kerravon, 23.10.2021, 01:50
      • MODE command - DosWorld, 01.11.2021, 19:05
        • MODE command - kerravon, 01.11.2021, 20:02
          • MODE command - tom, 02.11.2021, 18:53
            • MODE command - kerravon, 02.11.2021, 21:22