Texinfo files start with at least three lines that provide Info and
TeX with necessary information. These are the \input texinfo
line, the @settitle line, and the @setfilename line.
Also, if you want to format just part of the Texinfo file, you must
write the @settitle and @setfilename lines between
start-of-header and end-of-header lines. The start- and end-of-header
lines are optional, but they do no harm, so you might as well always
include them.
Any command that affects document formatting as a whole makes sense to
include in the header. @synindex (see synindex), for
instance, is another command often included in the header. See GNU Sample Texts, for complete sample texts.
Thus, the beginning of a Texinfo file generally looks like this:
\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename sample.info
@settitle Sample Manual 1.0
@c %**end of header