texinfo: Include Files Evolution

Include Files

Sample Include File

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20.5 Evolution of Include Files
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When Info was first created, it was customary to create many small Info
files on one subject.  Each Info file was formatted from its own Texinfo
source file.  This custom meant that Emacs did not need to make a large
buffer to hold the whole of a large Info file when someone wanted
information; instead, Emacs allocated just enough memory for the small
Info file that contained the particular information sought.  This way,
Emacs could avoid wasting memory.

  References from one file to another were made by referring to the file
name as well as the node name.  (*Note Referring to Other Info Files:
Other Info Files.  Also, see *note '@xref' with Four and Five Arguments:
Four and Five Arguments.)

  Include files were designed primarily as a way to create a single,
large printed manual out of several smaller Info files.  In a printed
manual, all the references were within the same document, so TeX could
automatically determine the references' page numbers.  The Info
formatting commands used include files only for creating joint indices;
each of the individual Texinfo files had to be formatted for Info
individually.  (Each, therefore, required its own '@setfilename' line.)

  However, because large Info files are now split automatically, it is
no longer necessary to keep them small.

  Nowadays, multiple Texinfo files are used mostly for large documents,
such as 'The GNU Emacs Lisp Reference Manual', and for projects in which
several different people write different sections of a document
simultaneously.

  In addition, the Info formatting commands have been extended to work
with the '@include' command so as to create a single large Info file
that is split into smaller files if necessary.  This means that you can
write menus and cross references without naming the different Texinfo
files.