Subdirectory Introduction

As the name implies, a pathname is nothing more than a "path" that directs DOS to your

particular file.

You see, with DOS 2.x, IBM/Microsoft introduced multiple directories on a single disk. In effect, this lets you sort your files into groups and place each related group into its own directory. This means you don't have to search an entire disk to find one file.

A lower-level directory is called a subdirectory (what else?)

Seriously, consider a disk. To this point you have learned that each file on that disk is represented as an entry in the directory, put there so both you and DOS can find the file on disk.

If, instead of data, you created a file that pointed to other files on the disk, you will have built what amounts to a subdirectory.

DOS manipulates files in subdirectories through several directory commands and what is called a pathname.

In this section we'll look at the DOS commands for manipulating subdirectories and how we can set an environment variable (PATH) to allow DOS to find programs.

The DOS directory structure can be thought of as a tree, with the master disk directory being called  the root and  subdirectories  thought  of as  branches.  The root  is  the hard  disk's  master directory. It may contain up to 512 entries. Subdirectories may contain any number of entries (until the disk is full). A floppy root directory may contain 112 or 224 entries. A typical tree might look like...

In the example there are five files and two subdirectories in the root. Each of the subdirectories has similar contents. SubDir1, for example, has three files and one subdirectory in it. This structure can be extended until the disk is completely full, subject only to the constraint of 63 characters for the pathname that you will use to find a particular file.

The rules for a subdirectory name are just like that for filenames (eight characters followed by a period and three character extension).

They show up in a directory listing with the designator <DIR> behind them. Let's see now how to build a pathname.

Pathnames

Assume the subdirectory structure (only directories are shown, not files)...

Root	Level 1 Subdirectory		Level 2 Subdirectory
C:\	WORDPROC		BOOK MEMOS LETTERS

This series of subdirectories was set up to categorize various files developed by a word processor. Let's move in the structure:

•    \WORDPROC\LETTERS Would be the pathname from the root to subdirectory LETTERS.

•    \WORDPROC Is the pathname from root to WORDPROC.

Note that each subdirectory in the path is separated by a backslash (\). The single backslash at the beginning of the pathname indicates the root. All pathnames must originate in either the current directory or root.

A test -- What is the pathname from the root to the subdirectories listed below?

•    Subdirectory LETTERS

•    Subdirectory BOOK

•    Subdirectory WORDPROC Answers...

•    \WORDPROC\LETTERS

•    \WORDPROC\BOOK

•    \WORDPROC

When  DOS  is  booted,  the  root  directory  is  automatically  selected.  To  type  a  file  named

MYMEMO.TXT in subdirectory MEMOS the command would be: C:\> TYPE \WORDPROC\MEMOS\MYMEMO.TXT

\WORDPROC\MEMOS\ is the pathname that DOS would use to find the file MYMEMO.TXT and then show it on the screen.

If  you've  got work  to  do with files in the MEMOS subdirectory, typing the complete pathname all the time would be inefficient. Therefore, DOS gives you a method of making DOS recognize the MEMOS directory as the default: the Change Directory command.

To change to the MEMOS subdirectory from the root the command would be: C:\> CD \WORDPROC\MEMOS

If set properly (see just below) the prompt might also change to reflect the change directory (C:\WORDPROC\MEMOS>, and a DIR command would now show the contents of the MEMOS subdirectory instead of the root and DOS would look for all command files in that subdirectory instead of the root.

An easy way to keep track of where you are in the directory tree is to use the PROMPT command to set a prompt that shows the current directory along with the current drive. You can easily do this by adding the line:

PROMPT $P$G

to your AUTOEXEC.BAT file.

Make and Remove Subdirectories

If you are going to have subdirectories, there must be a way to make them. The syntax for

the make directory command is:

MD d:pathname\DIRNAME

You can make a subdirectory IN any directory FROM any directory so long as you give the appropriate pathname. Usually, you will change to the directory you want the subdirectory to be in

and then issue a simple MD DIRNAME command. That way there is no mistake about what will happen.

When you no longer need a directory you may remove it from the disk. The first thing you have to do is empty it of files and move out of it. Only then will you be able to remove it. The syntax for removing is:

RD d:pathname\DIRNAME

You cannot remove the root directory (it's the master for the disk and when it's the only directory you would have to be in it, and you can't remove a directory you are in).

Note:  In DOS 6.0 the command DELTREE was introduced. DELTREE will both remove files from a directory and remove that directory with a single command.

Mysterious Dots

When you are in a subdirectory and issue the DIR command, you will see something like

this:

The dots indicate you are in a subdirectory. The single dot is the current directory and the double  dots  are  the  parent  to  the  current  directory.  Thus  you  could  move  to  the  parent  of TUTORIAL (in the example above) by simply issuing the command CD ..

Used with care, the dots can speed up subdirectory commands.

Tree

All directory paths and their relationships are called a tree. If you don't remember the

various subdirectories (and optionally the files in them) DOS offers you a chance to see them with the TREE command:

TREE d:/f

This command lists all paths from the root on the disk. If you use the /f option, you will also see  all  files  in  each  subdirectory.  (Only  the  filenames  are  shown,  not  their  size  or  creation date/time.)

For a permanent record, press Control-PrtScr before issuing the TREE command and again after. Your printer will record all text scrolling past on the screen. (Or redirect to a file with TREE d:/f > Filename.)

[Note: TREE has been removed under Windows.]