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Continuing my reading of Dan Gookin's MS-DOS 6 pour les nuls (More DOS for Dummies ?), I've discovered in an otherwise light and funny (at least the French translation is) book about DOS a section where he mentions some commands that no one is supposed to use and particularly RECOVER. The way he talks about it and urges users to delete it, made me conclude that he had a bad experience with it.

I started with MS-DOS 6.22 so it wasn't there, I've read the Wikipedia article about it and from what I've understood that it was supposed to fix lost partitions but made the disk unbootable.

Am I right? How did it do that? And in that line, if it becomes unbootable how can someone get what was fixed?

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    Programs that could recover lost files from the scraps of the retrieval info left on a corrupted disk are ancient. I wrote such a program for DECtapes under TOPS-10 in 1969. My program was in response to a sudden crisis at my place of work. Commented Dec 18, 2022 at 11:20

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It was not meant to repair volumes, but to recover data from them, hence the name.

PhotoRec is a more modern (and much more sophisticated) tool with a similar purpose. There's a crucial difference: PhotoRec doesn't modify the ailing volume. It saves whatever it finds to a different volume. MS-DOS's recover didn't read the file data and save it elsewhere; it just created directory entries on the same volume that pointed to where the data already was. Those entries replaced the directory entries that were already on the volume—even though one of those old entries might have pointed to the same file, and had other useful information like the file's original name. So it could easily do more harm than good.

A disk wouldn't boot after running recover on it because the bootloader expects to find a file named io.sys (or ibmbio.com), and the only files left on the volume after recover ran had names like file1234.rec.

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    Upvoted, I remember 2 hidden files in C:\ MSDOS.SYS and IO.SYS, how can someone access the drive then? Floppy boot? Attaching it as a slave on IDE? Commented Dec 17, 2022 at 18:26
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    @user10191234 Yes, you could boot from another disk. Unbootable floppies were common anyway.
    – benrg
    Commented Dec 17, 2022 at 19:15

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