Chapter
1
I
System Calls
There is no restriction in MS-DOS on the depth
of
a tree (the
length of the longest path from
root
to
leaf) except in the number
of allocation units available. The
root
directory will have a fixed
number of entries.
For
non-root directories,
the
number of
files
per directory is limited only by the number
of
allocation units
available.
Subdirectories of the root have a special attribute set indicating
that they are directories. The subdirectories themselves are files,
linked through the File Allocation Table (FAT). Their contents
are identical in character
to
the contents of the root directory.
Attributes apply
to
the tree-structured directories in the follow-
ing manner:
Attribute Meaning/Function MeaningIFunction
for files for directories
volume id Present at the
root.
Meaningless.
Only
1
file may have
this set.
directory Meaningless. Indicates that the
directory entry
is
a
directory. Cannot be
changed with Func-
tion Call
43H.
read only Old create, new cre- Meaningless.
ate, new open (for
write or readlwrite)
will fail.
archive Set when file is Meaningless.
written. Setireset
via Function
43H.
hidden/ Prevents file from Prevents directory
system system being found entry from being
in search first/ found. Function
3BH
search next. Old will still work..
open will fail.
11
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