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Peter Swinkels Thu Sep 19 2024 at 1:22 pm
CLOCK$ device file in MS-DOS

Playing around with MS-DOS in DOSBox I tried reading from the CLOCK$ device file in QBasic as if it were a regular file.

Either I get the same character over and over again or it crashes, with a memory error such as "Out of string space" or something to the effect of the memory having been corrupted.

Does anyone know what this device file is for and how it should be used?

CLOCK$ device file in MS-DOS - Peter Swinkels (Thu Sep 19 2024 at 1:22 pm)

DOSBox does not implement CLOCK$ - Plasma (Mon Sep 23 2024 at 10:51 pm)
- A small QBasic program that can read from CLOCK$-> - Peter Swinkels (Tue Oct 1 2024 at 2:09 pm)
  - And here is a version written in C-> - Peter Swinkels (Fri Oct 11 2024 at 2:52 pm)
    - what value is fread returning? * - Plasma (Sun Oct 20 2024 at 9:31 pm)
      - Okay I figured it out. - Peter Swinkels (Thu Oct 24 2024 at 1:09 pm)
        maybe sizeof(struct ClockStr)? - Plasma (Thu Oct 24 2024 at 6:37 pm)
        Now why didn't I think of that? It works! * - Peter Swinkels (Fri Oct 25 2024 at 4:24 am)
        nice * - Plasma (Fri Oct 25 2024 at 10:51 am)
      - You mean what value of fread is returning?-> - Peter Swinkels (Thu Oct 24 2024 at 3:50 am)
      - You mean what value of fread is returning?-> - Peter Swinkels (Thu Oct 24 2024 at 3:50 am)
  - what was the issue - Plasma (Wed Oct 2 2024 at 11:09 am)
    - Not sure but-> - Peter Swinkels (Wed Oct 2 2024 at 3:29 pm)
      - Did some testing. - Peter Swinkels (Thu Oct 3 2024 at 1:18 pm)
        Maybe QB is letting you read past the end of the "file" - Plasma (Thu Oct 3 2024 at 6:53 pm)
        I did some more testing with some interesting results-> - Peter Swinkels (Fri Oct 4 2024 at 1:00 pm)
        strange - Plasma (Fri Oct 4 2024 at 3:08 pm)
        Some more tests: - Peter Swinkels (Sat Oct 5 2024 at 12:17 pm)
        Narrowed it down-> - Peter Swinkels (Sat Oct 5 2024 at 12:22 pm)
        even INPUT$(1, FileH) crashes? * - Plasma (Mon Oct 7 2024 at 9:54 am)
        Repeated uses of INPUT$ with very small buffer causes crashes-> - Peter Swinkels (Mon Oct 7 2024 at 1:00 pm)
        I think the actual INPUT$ buffer is internal - Plasma (Mon Oct 7 2024 at 4:51 pm)
        Here's a quick test I wrote in C-> - Peter Swinkels (Thu Oct 10 2024 at 1:42 pm)
        ftell-> - Peter Swinkels (Fri Oct 11 2024 at 2:58 pm)
        
        See-> - Peter Swinkels (Fri Oct 11 2024 at 2:53 pm)
        
        Well-> - Peter Swinkels (Sat Oct 5 2024 at 3:50 am)
- sec/100 ? - Peter Swinkels (Tue Oct 1 2024 at 1:58 pm)
  - Never mind. - Peter Swinkels (Tue Oct 1 2024 at 2:03 pm)
- I was using actual MS-DOS 6.22-> - Peter Swinkels (Tue Oct 1 2024 at 3:19 am)
  - I see - Plasma (Wed Oct 2 2024 at 11:00 am)
    - Ah I see, - Peter Swinkels (Wed Oct 2 2024 at 3:37 pm)
      - yep * - Plasma (Wed Oct 2 2024 at 8:13 pm)

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