Attribute Definition File

<title>Attribute Definition File</title>
File 4 is $AttrDef, which contains the attribute names for all attributes
used on the volume. Currently, only the <a href=attr.html>well-known</a>
attributes should appear. Each record in this file has A0 bytes
<pre>
Offset(length)    Description
0(80)             Attribute name (Unicode)
80(8)             Attribute ID
88(8)             Flags
90(8)             Minimum allowed size
98(8)             Maximum allowed size
</pre>
<i> The exact meaning of the flags is still not clear. Most likely,
bit 7 means 'may be non-resident', and bit 1 'indexable'. Bit 6 is also
in use, all other flags are zero for the available attributes.</i>