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A directory ID or DID is the File ID of a directory file.

Under some circumstances, a full file specification may contain more characters than the 255 bytes allowed by unmodified applications. If a file specification that such an application needs exceeds 255 bytes in length, RMS generates a shorter file specification by abbreviating the directory to a Directory ID (DID), and if necessary, the filename to a File ID (FID).

When the file specification is too long, RMS first attempts to generate a shorter directory specification by identifying the directory with its directory ID. This shorter specification is referred to as a DID.

$ dir test.dir /file

Directory DKA200:[000000]

test.dir;1           (11,1,0)

Total of 1 file.
$ dir [11,1,0]

Directory DKA200:[11,1,0]

test.com;7          test.com;6          test.com;5          test.com;4
test.com;3          test.com;2          test.com;1

Total of 7 files.

Note that this form of the directory name must have three numbers and two commas to avoid ambiguity with UIC format directory names. With the DIRECTORY command you can view the shorter DID version as well as the full version of a file specification.