By convention, the name of a Texinfo file ends with one of the extensions .texinfo, .texi, .txi, or .tex.2
In order to be made into a printed manual and other output formats, a Texinfo file must begin with lines like this:
\input texinfo @settitle name-of-manual
The contents of the file follow this beginning, and then you must end the Texinfo source with a line like this:
Here’s an explanation:
@settitleline specifies a title for the page headers (or footers) of the printed manual, and the default title and document description for the ‘<head>’ in HTML. Strictly speaking,
@settitleis optional—if you don’t mind your document being titled ‘Untitled’.
@byeline at the end of the file on a line of its own tells the formatters that the file is ended and to stop formatting. If you leave this out, you’ll be dumped at TeX’s prompt at the end of the run.
Furthermore, you will usually provide a Texinfo file with a title page, indices, and the like, all of which are explained in this manual. But the minimum, which can be useful for short documents, is just the two lines at the beginning and the one line at the end.
The longer extensions are preferred, since they describe more clearly to a human reader the nature of the file. The shorter extensions are for operating systems that cannot handle long file names.