Any node in the Info hierarchy may have a menu--a list of subnodes. The m command searches the current node's menu for the topic which it reads from the terminal.
A menu begins with a line starting with * Menu:. The rest of the
line is a comment. After the starting line, every line that begins
with a * lists a single topic. The name of the topic-what
the user must type at the m's command prompt to select this
topic--comes right after the star and space, and is followed by a
colon, spaces and tabs, and the name of the node which discusses that
topic. The node name, like node names following Next, Previous
and Up, may be terminated with a tab, comma, or newline; it may also
be terminated with a period.
If the node name and topic name are the same, then rather than
giving the name twice, the abbreviation * name:: may be
used (and should be used, whenever possible, as it reduces the visual
clutter in the menu).
It is considerate to choose the topic names so that they differ from each other very near the beginning--this allows the user to type short abbreviations. In a long menu, it is a good idea to capitalize the beginning of each item name which is the minimum acceptable abbreviation for it (a long menu is more than 5 or so entries).
The nodes listed in a node's menu are called its "subnodes", and it
is their "superior". They should each have an Up: pointing at
the superior. It is often useful to arrange all or most of the subnodes
in a sequence of Next and Previous pointers so that
someone who wants to see them all need not keep revisiting the Menu.
The Info Directory is simply the menu of the node (dir)Top--that
is, node Top in file .../info/dir. You can put new entries
in that menu just like any other menu. The Info Directory is not the
same as the file directory called info. It happens that many of
Info's files live in that file directory, but they do not have to; and
files in that directory are not automatically listed in the Info
Directory node.
Also, although the Info node graph is claimed to be a "hierarchy",
in fact it can be any directed graph. Shared structures and
pointer cycles are perfectly possible, and can be used if they are
appropriate to the meaning to be expressed. There is no need for all
the nodes in a file to form a connected structure. In fact, this file
has two connected components. You are in one of them, which is under
the node Top; the other contains the node Help which the
h command goes to. In fact, since there is no garbage
collector, nothing terrible happens if a substructure is not pointed
to, but such a substructure is rather useless since nobody can
ever find out that it exists.