DOS ain't dead

zoo files extraction (Users)

posted by mceric, Germany, 26.01.2024, 21:19

> it might check the available disk space before unpacking a file
> and expect a value below 2GB or overflow otherwise.

Good thought! However, according to RBIL, the FAT12/FAT16 function int 21h with ah=36h should report "2 GB - 32 KB" if more space than that is available, exactly to avoid this kind of problem with programs which might interpret values between 2 GB and 4 GB as negative signed integers.

The FAT32 call is int 21h with ax=7303h, by the way, "get extended free space on drive". Interestingly, Win9x even clips the reported number of free FAT32 clusters to 64k if DOS TSR are active, effectively also limiting reported free space to 2 GB, according to RBIL.

Apps which work on really old DOS versions could also use int 21h, function ah=1bh or 1ch, but those should only report disk, sector and cluster size, not free space on disk. RBIL says those functions report wrong values in Win9x.

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FreeDOS / DOSEMU2 / ...

Complete thread:

• zoo files extraction - fritz.mueller, 26.01.2024, 17:17
  • zoo files extraction - RayeR, 26.01.2024, 17:21
    • zoo files extraction - Ringding, 26.01.2024, 17:38
      • zoo files extraction - mceric, 26.01.2024, 21:19
  • zoo files extraction - jadoxa, 27.01.2024, 03:55
    • zoo files extraction - mceric, 27.01.2024, 12:01
      • zoo files extraction - fritz.mueller, 27.01.2024, 19:10
        • zoo files extraction - Rugxulo, 27.01.2024, 21:42
          • zoo files extraction - Rugxulo, 28.01.2024, 15:34
        • zoo cluster size overflow vs chkdsk or scandisk for fat32 - mceric, 27.01.2024, 21:48
          • zoo cluster size overflow vs chkdsk or scandisk for fat32 - Ringding, 28.01.2024, 20:13
            • zoo cluster size overflow vs chkdsk or scandisk for fat32 - Rugxulo, 28.01.2024, 22:53
            • zoo cluster size overflow vs chkdsk or scandisk for fat32 - RayeR, 29.01.2024, 06:29
              • zoo cluster size overflow vs chkdsk or scandisk for fat32 - rr, 29.01.2024, 08:45
              • zoo cluster size overflow vs chkdsk or scandisk for fat32 - Ringding, 29.01.2024, 09:03
                • zoo cluster size overflow vs chkdsk or scandisk for fat32 - RayeR, 29.01.2024, 13:45
                  • zoo cluster size overflow vs chkdsk or scandisk for fat32 - fritz.mueller, 29.01.2024, 18:52
                • zoo cluster size overflow vs chkdsk or scandisk for fat32 - Rugxulo, 29.01.2024, 21:02
          • zoo cluster size overflow vs chkdsk or scandisk for fat32 - rr, 29.01.2024, 08:55
            • zoo cluster size overflow vs chkdsk or scandisk for fat32 - roytam, 29.01.2024, 10:06
              • zoo cluster size overflow vs chkdsk or scandisk for fat32 - rr, 29.01.2024, 19:07
      • zoo files extraction - RayeR, 28.01.2024, 15:05
        • zoo files extraction - Ringding, 28.01.2024, 20:22
          • zoo files extraction - fritz.mueller, 28.01.2024, 22:21