## 16.3 Raw Formatter Commands

Inside a region delineated by `@iftex` and `@end iftex`, you can embed some raw TeX commands. Info will ignore these commands since they are only in that part of the file which is seen by TeX. You can write the TeX commands as you would write them in a normal TeX file, except that you must replace the ‘`\`’ used by TeX with an ‘`@`’. For example, in the `@titlepage` section of a Texinfo file, you can use the TeX command `@vskip` to format the copyright page. (The `@titlepage` command causes Info to ignore the region automatically, as it does with the `@iftex` command.)

However, many features of plain TeX will not work, as they are overridden by Texinfo features.

You can enter plain TeX completely, and use ‘`\`’ in the TeX commands, by delineating a region with the `@tex` and `@end tex` commands. (The `@tex` command also causes Info to ignore the region, like the `@iftex` command.) The sole exception is that the `@` character still introduces a command, so that `@end tex` can be recognized properly.

For example, here is a mathematical expression written in plain TeX:

    @tex
    $$ \chi^2 = \sum_{i=1}^N
              \left (y_i - (a + b x_i)
              \over \sigma_i\right)^2 $$
    @end tex

The output of this example will appear only in a printed manual. If you are reading this in Info, you will not see the equation that appears in the printed manual.

Analogously, you can use `@ifhtml … @end ifhtml` to delimit a region to be included in HTML output only, and `@html … @end html` for a region of raw HTML (again, except that `@` is still the escape character, so the `@end` command can be recognized.)

This document was generated on a sunny day using texi2html.