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Format of MS-DOS 7/Windows95 long-filename directory entry

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Offset Size Description

00h

BYTE

LFN record sequence and flags
bits 5 - 0 : sequence number
bit 6 : set if last long-filename record for file
bit 7 : set if file deleted

01h

10 BYTEs

long filename, first part

0Bh

BYTE

0Fh (otherwise impossible file attribute, used as signature)

0Ch

BYTE

reserved??? (00h)

0Dh

BYTE

checksum for short filename

0Eh

12 BYTEs

long filename, second part

1Ah

WORD

first cluster number (always 0000h for LFN records)

1Ch

4 BYTEs

long filename, third part

Note:

Long-filename entries are always stored in the directory just prior to the short-name entry for a file.
Multiple LFN records are used if the long filename does not fit into a single record.
The short-filename checksum byte is computed by adding up the eleven bytes of the short filename, rotating the intermediate sum right one bit before adding the next character.
The long filename is encoded as 16-bit Unicode characters; for most filenames, this appears in the directory as the ASCII character followed by 00h.

See Also:

#01352,INT 21/AX=5704h,INT 21/AH=71h