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What does dd stand for? I've always referred to it colloquially as "Disk Destroyer", but what are the "official" words that make up the acronym/command?

According to this link and this link it could be one of the following:

  1. It used to stand for 'copy and convert' and was renamed 'dd' because 'cc' was already in use for the C compiler.
  2. It is a remnant of 'Job Control Language' program conversion into the 'Job Entry System'.
  3. It means 'data destruction'
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    I've always been told it meant Dump Data, being a unix command to dump disk files to magnetic tape (long ago pre in pre-Linux days when sending data by tape was still common). That's what I was told back at uni (or at least my memory of it), and I see no connection at all with the IBM JCL DD .. as its descriptive in MVS JCL only, and doesn't at all relate to COPY etc; as how its used [in JCL] will be defined elsewhere in the JCL being descriptive only (links JCL reference to the DSN in IBM/MVS terms)
    – guiverc
    Commented Sep 8, 2023 at 7:44

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The actual definition may have been a joke, keyboard shorthand, or obscure reference. Wikipedia has this:

The name dd may be an allusion to the DD statement found in IBM's Job Control Language (JCL),[3] where the initials stand for "Data Description."[4] The command's syntax resembles the JCL statement more than it does other Unix commands, so the syntax may have been a joke.[3] Another explanation for the command's name is that "cc" (for "convert and copy", as in the command's description) was already taken by the C compiler. It is also jokingly said that dd stands for "disk destroyer" or "delete data", since when used for low-level operations on hard disks, a small mistake such as reversing the input file and output file parameters could result in the loss of some or all data on a disk.

Source: dd (unix) on en.wikipedia.org

This page on codecoffee has some additional discussion.

Many sysadmins have come up with their own mnemonics for commands like dd(1), and, in this case, it seems pretty much anything goes!

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    I like disk destroyer personally Commented Oct 24, 2019 at 15:24

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