20.2.1 The Directory File `dir'
-------------------------------

For Info to work, the `info' directory must contain a file that
serves as a top level directory for the Info system.  By convention,
this file is called `dir'.  (You can find the location of this file
within Emacs by typing C-h i to enter Info and then typing
C-x C-f to see the pathname to the `info' directory.)

The `dir' file is itself an Info file.  It contains the top level
menu for all the Info files in the system.  The menu looks like
this:

* Menu:
* Info:    (info).     Documentation browsing system.
* Emacs:   (emacs).    The extensible, self-documenting
                       text editor.
* Texinfo: (texinfo).  With one source file, make
                       either a printed manual using
                       @TeX{} or an Info file.
...

Each of these menu entries points to the `Top' node of the Info file
that is named in parentheses.  (The menu entry does not need to
specify the `Top' node, since Info goes to the `Top' node if no node
name is mentioned.  See Nodes in Other Info Files.)

Thus, the `Info' entry points to the `Top' node of the
`info' file and the `Emacs' entry points to the `Top' node
of the `emacs' file.

In each of the Info files, the `Up' pointer of the `Top' node refers
back to the dir file.  For example, the line for the `Top'
node of the Emacs manual looks like this in Info:

File: emacs  Node: Top, Up: (DIR), Next: Distrib

In this case, the `dir' file name is written in upper case
letters--it can be written in either upper or lower case.  This is not
true in general, it is a special case for `dir'.


