Technical information

© Jean Louis-Guérin – V1.2a – September 2014 Page 58 / 69
FAT16, used for dirty volume management: high order bit 1: last shutdown was clean; next highest bit
1: during the previous mount no disk I/O errors were detected.
10.6.4 DOS/FAT Directory Table
A Directory Table is a special type of file that represents a directory (also known as a folder). Each
file or directory stored within it is represented by a 32-byte entry in the table. Each entry records the
name, extension, attributes (archive, directory, hidden, read-only, system and volume), the date and
time of creation, the address of the first cluster of the file/directory's data and finally the size of the
file/directory. Aside from the Root Directory Table in FAT12 and FAT16 file systems, which occupies
the special Root Directory region location, all Directory Tables are stored in the Data region. The
actual number of entries in a directory stored in the Data region can grow by adding another cluster to
the chain in the FAT.
Legal characters for DOS file names include the following:
 Upper case letters A–Z
 Numbers 0–9
 Space (though trailing spaces in either the base name or the extension are considered to be
padding and not a part of the file name, also filenames with space in them could not be used on the
DOS command line prior to Windows 95 because of the lack of a suitable escaping system)
 ! # $ % & ' ( ) - @ ^ _ ` { } ~
 Values 128–255
This excludes the following ASCII characters:
 " * / : < > ? \ |
Windows/MSDOS has no shell escape character
 + , . ; = [ ]
They are allowed in long file names only.
 Lower case letters a–z
Stored as A–Z. Allowed in long file names.
 Control characters 0–31
 Value 127 (DEL)