File Systems
Each disk volume is organized according to a file system. The file system
determines how files are named and how they are organized on the disk.
As hard disk technology and operating systems have evolved, new file
systems have been invented to support longer file names, larger drives,
and higher disk performance. Several different and incompatible schemes
have evolved. Which file systems you can use depends on which operating
system you are using, and how the operating system and your hard disk are
configured.
The operating systems under which CMD.EXE runs can support two standard
file systems: FAT and HPFS. See File Names for details on the rules for
naming files under each file system.
* The FAT File System is the traditional file system used by all
versions of DOS. Its name comes from the File Allocation Table
DOS uses to keep track of the space allocated to each file.
Windows 95, Windows NT, and OS/2 also support the FAT file
system.
* The High Performance File System or HPFS is a file system provided
with all versions of OS/2, and is also supported in Windows NT
version 3.51 and below. It supports long file names, and offers
higher performance and better support for large drives than the
FAT system. It also supports "extended attributes" to retain
additional information about your files.
DOS sessions running under OS/2 can access files on HPFS drives if
the files have short, FAT-compatible names. Other operating
systems (DOS, Windows 95, and Windows NT 4.0 and above) can not
access files on HPFS drives.
Additional file systems may be installed under some operating systems to
support CD-ROM or network drives. The file system type (FAT or HPFS) is
determined when a hard disk volume is formatted and applies to the entire
volume. For example, under OS/2 you might have a 2 GB hard disk divided
into four 500 MB volumes, with the first three volumes (C:, D:, and E:)
formatted for the FAT file system, and the fourth formatted for HPFS.
CMD.EXE supports any standard file system installed under your operating
system. If your operating system can access files on a particular drive,
then CMD.EXE will be able to access those files as well.
Additional information about disk files and directories is available
under Drives and Volumes, Directories and Subdirectories, File Names, and
File Attributes and Time Stamps.
Network File Systems
A network file system allows you to access files stored on another
computer on a network, rather than on your own system. CMD.EXE supports
all network file systems which are compatible with the underlying
operating system.
File and directory names for network file systems depend on both the
"server" software running on the system that has the files on it, and the
"client" software running on your computer to connect it to the network.
However, they usually follow the rules described under File Names.
Most network software "maps" unused drive letters on your system to
specific locations on the network, and you can then treat the drive as if
it were physically part of your local computer.
Some networks also support the Universal Naming Convention, which
provides a common method for accessing files on a network drive without
using a "mapped" drive letter. Names specified this way are called UNC
names. They typically appear as \\server\volume\path\filename, where server
is the name of the network server where the files reside, volume is the
name of a disk volume on that server, and the path\filename portion is a
directory name and file name which follow the conventions described in
Directories and Subdirectories. CMD.EXE supports UNC filenames, and also
allows you to use UNC directory names when changing directories (see
Directory Navigation for more details).
When you use a network file system, remember that the naming conventions
for files on the network may not match those on your local system. For
example, your local system may support long filenames while the network
server or client software does not, or vice versa. CMD.EXE will usually
handle whatever naming conventions are supported by your network
software, as long as the network software accurately reports the types of
names it can handle.
In rare cases, CMD.EXE may not be able to report correct statistics on
network drives (such as the number of bytes free on a drive). This is
usually because the network file system does not provide complete or
accurate information.
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