#Default Drive:  The disk drive that will be used by default.  In most DOS
commands, if you omit the drive letter, DOS assumes the default drive is to be
used.  The DOS prompt "d>", where "d" is a letter indicates which drive is the
default.

For example,  A>  means drive A is the default.

You may change the default drive by entering the drive letter followed by a
colon.

For example, to change the default drive from A to B, enter:

         B: [Return]

   The DOS prompt will now show B>
#Device Names:  Standard names used by DOS to identify hardware devices.

     CON           - console (keyboard/screen)
     COM1 (or AUX) - first asynchronous communications port
     COM2          - second asynchronous communications port
     LPT1 (or PRN) - first parallel printer
     LPT2          - second parallel printer
     LPT3          - third parallel printer
     NUL           - nonexistent device for application testing
#Directory:  A file used by DOS to keep track of files and subdirectories.  The
directory contains the names of files, their size (in bytes), the time and date
they were last written and the names of any subdirectories.  The DIR (Directory)
command displays directory information.

See also CURRENT DIRECTORY, DIRECTORY PATH and SUBDIRECTORY.
#Directory Path:  A series of directory names which tell DOS where to find a
particular directory.  The directory path begins with the name of a subdirectory
of the current directory, or with the root directory (indicated with a "\").
The last directory in the directory path is the directory to be used.

The maximum length of a directory path, (including \ characters) is 63
characters.

If a directory path is followed by a filename, you must place a \ between the
last directory name and the filename.

EXAMPLES:

\BUDGET\DATA\MYFILE.DAT - specifies that the file MYFILE.DAT is to be used.
MYFILE.DAT is in the DATA directory.  DATA is a subdirectory of the BUDGET
directory.  BUDGET is a subdirectory of the root (\) directory.

DATA\MYFILE.DAT - specifies that the file MYFILE.DAT is to be used.  MYFILE.DAT
is in the DATA directory.  DATA is a subdirectory of the current directory.
#DOS:  Disk Operating System.  DOS provides the instructions necessary for the
computer to operate.  It also contains a set of utility tools (Commands, the
Batch Facility, Special Keyboard keys and others) which allow you organize and
manage your applications.
#Drive Letter:  A letter which identifies a disk drive to DOS.  Each drive is
assigned a drive letter.  On a single drive system, the drive is assigned "A".
On a two drive system the left drive is "A" and the right drive is "B".  A fixed
drive is known as "C".
#End-Of-File-Marker:  A special ASCII code used by DOS to denote the end of a
file.  This character is Ctrl-Z (Hex 1A).
#Exit Code:  A numeric value produced by some DOS commands which indicates what
occurred during the command's execution.  This is useful in batch files to
allow action to be taken based upon the success or failure of a command.  For
example, the RESTORE command has these exit codes:

    0 - Normal completion           3 - Terminated by user
    1 - No files found to restore   4 - Terminated due to error

When the RESTORE command finishes, it sets the ERRORLEVEL variable to the exit
code value.  The Batch Subcommand IF may then be used to test the value of
ERRORLEVEL and take appropriate action.
#External Command:  A DOS command that resides in a disk file.  DOS has
"internal" and "external" commands.  Internal commands are stored in memory and
can be executed even if a diskette containing DOS is not in use.  To execute an
external command, a disk containing the command file must be in use.  The
filenames of external commands are the same as the name of the command.  The
filename extensions are either COM or EXE.  For example, the FORMAT command is
stored on the DOS diskette as FORMAT.COM.  The SORT command is stored as
SORT.EXE.

See also INTERNAL COMMAND.
