                           Overview of DOS Commands

DOS has a set of utility programs known as "DOS Commands."  These utility
programs perform special functions which help you organize and operate your
applications.

To execute a DOS command, you type the name of the command followed by one or
more "parameters" (items).  Some commands, such as CLS (to clear the screen),
have no parameters.  To execute CLS you simply type CLS and press the return
key.  Most commands, however, have several parameters that can be entered.  The
parameters give the command specific instructions about the task to be
performed.

Some command parameters are required, some are optional, some are choices and
others may be repeated as needed.  In all cases, the order in which the
parameters are entered is important.  The parameters must be entered in the
particular order that the command understands.

To explain the parameters of DOS commands, a special notation is used in DOS
reference material.  This notation, called the "Format Notation," shows all the
parameters of a command, the order in which they are entered, and whether they
are required, optional, choices and so on.

HelpDOS uses the same Format Notation as the DOS manual.  It is important that
you understand the simple rules used in the Format Notation.  By understanding
the Format Notation you can easily interpret how a command should be entered.

The Format Notation rules are explained below.  They are also summarized in
HelpDOS' help window (activated with F1) for quick reference.


                            Format Notation Rules

KEYWORDS:  Keywords are shown in capital letters.  Keywords must be entered as
   shown.  You may enter keywords in any combination of upper and lower case
   letters.

LOWERCASE LETTERS:  You supply the items shown in lowercase letters.  For
   example, where "filename" appears, you substitute the name of your file.  You
   may enter your items in any combination of upper and lower case letters
   (unless specified otherwise in the help text).

BRACKETS [ ]:  Items in brackets are optional.  If you include optional items,
   you supply only the information inside the brackets.  The brackets are not a
   part of the command, they are used for Format Notation only.

BAR |:  Items separated by a bar are choices.  The bar means "or."  For example,
   ON | OFF means you may enter ON or OFF, but not both.  The bar is not a part
   of the command, it is used for Format Notation only.

ELLIPSIS (...) :  Three periods indicate you may repeat the previous item as
   many times as you need.  This notation applies only to a few commands.  The
   periods are not a part of the command, they are used for Format Notation
   only.


                           Format Notation Examples

In the CHDIR (change directory) command both parameters, d: and path, are
optional since they are enclosed in brackets.

          CHDIR [d:][path]


In the RMDIR (remove directory) command, the parameter d: is optional but the
path must be specified.

          RMDIR [d:]path


The BREAK command has one optional parameter, which can be either of the
Keywords ON or OFF, but not both.  You could enter BREAK, (with no parameter),
BREAK ON or BREAK OFF.  Note that BREAK ON OFF would be invalid.

          BREAK [ON | OFF]


The ASSIGN command illustrates the Ellipsis notation (...), which indicates
that the previous parameter, [x=y] may be repeated as many times as needed.
Valid uses of ASSIGN are:  ASSIGN (with no parameters), ASSIGN a=b,
ASSIGN a=b b=c, ASSIGN a=b b=c c=d, and so on.

          ASSIGN [x=y [...]]


                     Default Drive and Directory Path

For many DOS commands, specifying a disk drive letter is optional.  This is
shown in the format of a command by [d:]. If you omit an optional drive letter,
DOS assumes the default drive is to be used.  For example, if the default drive
is A and you want to see a directory list for the disk in drive B, you must
specify the drive letter, as in DIR B:  But if you want to see the directory for
the disk in the default drive, you may omit the drive letter, and enter just
DIR.

Similarly, for many DOS commands, specifying the directory path is optional.
This is shown in the format of a command by [path].  If you do not specify a
directory path, DOS will assume the current directory is to be used.


                       Internal and External Commands

DOS commands are either "internal" or "external."  Internal commands are
resident in memory and may be executed at any time under DOS.  External commands
reside on disk and are loaded into memory for execution.  The files of external
commands are called "command files" and have the filename extension of .COM or
.EXE.  For example, the file containing the DISKCOMP command is DISKCOMP.COM.  A
disk containing the appropriate command file must be in use for an external
command to be executed.

In the HelpDOS help files, the first line tells if the command is internal or
external.  Below is the first line of the help text for the DISKCOMP command.

      ---------------  DISKCOMP - External DOS Command  ---------------

This indicates that the help text is for DISKCOMP, and that DISKCOMP is an
external DOS command.
