[Toc][Index]

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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