Directory

A floppy disk or a hard disk is a relatively large storage area which can store hundreds of files. It is similar to the rack kept in your school's office, where files concerning your fees, tests etc. are kept.
Let's compare your office rack with a hard disk. A rack has different rows. Depending on the requirement, you can divide a row into cabinets (or Sub-rows). A rack can be compared with a disk and the directory can be compared with a row. A directory is nothing but an index of the files stored on a disk. It contains information about all files stored on a disk. This includes the name (with extension), size, date of creation, date of last updates, time of creation.
As number of files increases, it is difficult for your school staff to manage the file. Hence, he or she keeps files of different classes in different rows, as for instance, the last row contains files of class X, second last row contains files of  class IX, and so on.
Similarly, in computer also, when the number of file increases, it is difficult to mange them. So we need the division of directory (i.e. sub-directory). A sub directory is a directory within directory. With the help of sub-directories we can reorganize our file in such a way that the files of class X can be kept in a sub-directory named class X, files of class IX can be kept in a sub-directory named class IX and so on.
Many sub-directories can be made on the disk, but the basic directory on the disk is always the main directory called the root directory. This directory is always designated by a backslash (\). You can create sub-directory of the root directory. Each sub directory can be subdivided into more sub sub-directories, each divided from its parent directory by a backslash In this way, an inverted tree structure is created which is known as directory tree of a disk.
Inside the root directory (C:\), we have created sub-directory NEPAL. Inside NEPAL, four sub directories MECHI, KOSHI, JANAKPUR, BAGMATI are created. Inside BAGMATI 8 more sub directories are created KATHMANDU,  BHAKTAPUR,  RASHUWA, DHADING, SINDHUPALCHOWK, KABRE, LALITPUR. Inside KATHMANDU SCHOOL-X, SCHOOL-Y, SCHOOL-Z are created and inside SCHOOL-X, CLASS-IX, CLASS-X are created.
 The operating system manges a directory in the same way, as rule for writing directory names :
1. Directory name can  not have more than 8 characters.
2. Directory name can have extension (or point and upto 3 characters if required).
3. Blank space is not allowed.
4. Both capital and small letters are allowed.

Advantages of Directories

• Orderly layout (a management of files) 
• Quicker access to files
• The command covers specified or current directory.