In the earlier part of this DOS tutorial you learned the basics of files and DOS commands. Recall that many of these commands had filenames as either part of the command or an option to the command.

Given the limited capacity of floppy disks, this rarely posed a problem. To find the necessary filename all you have to do is call up a DIRectory. For hard disks, however, with their large storage capacity, a directory listing could take considerable time to complete if you had to go through each and every file name on the disk.

The solution that Microsoft came up with in their DOS 2.0 or later is the addition of pathnames and subdirectories.

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.

Let's look first at how DOS organizes subdirectories and then the commands that deal with them.

Subdirectory Commands