Ms-Dos Disk Directory - Tandy 1000 Programmer's Reference Manual

Chapter 4 I
MS-DOS Disk Allocation
MS-DOS Disk Directory
FORMAT builds the root directory for all disks. Its location on
disk and the maximum number of entries are dependent on the
media.
Since directories other than the root directory are regarded as
files by MS-DOS, there is no limit to the number of entries they
may contain.
All directory entries are 32 bytes in length, and are in the fol-
lowing format:
OOH-07H
Filename. 8 characters, left-aligned and padded, if
necessary, with blanks. The first byte of this field
indicates the file status as follows:
O O H
E5H
2EH
The directory entry has never been used.
This is used to limit the length of directory
searches, for performance reasons.
The directory entry has been used, but the
file has been erased.
The entry is for a directory. If the second
byte is also 2EH, then the cluster field con-
tains the cluster number of this directory's
parent directory (0000H if the parent direc-
tory is the root directory). Otherwise, bytes
OIH through OAH are all spaces, and the
cluster field contains the cluster number of
this directory.
Any other character is the first character of a filename.
08H-0AH Filename extension.
O B File Attribute. The attribute byte is mapped as
follows:
OIH File is marked read only. An attempt to
open the file for writing using the Open
File function call (function call 3DH) re-
sults in an error code returned. This value
can be used along with other values below.
Attempts to delete the file with the Delete
File (13H) or Delete a Directory Entry
(41H) function call will also fail.
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