## Preparing to Use TeX

TeX needs to know where to find the `texinfo.tex' file that you have told it to input with the `\input texinfo' command at the beginning of the first line. The `texinfo.tex' file tells TeX how to handle @-commands. (`texinfo.tex' is included in the standard GNU distributions.)

Usually, the `texinfo.tex' file is put in the default directory that contains TeX macros (the `/usr/lib/tex/macros' directory) when GNU Emacs or other GNU software is installed. In this case, TeX will find the file and you do not need to do anything special. Alternatively, you can put `texinfo.tex' in the directory in which the Texinfo source file is located, and TeX will find it there.

However, you may want to specify the location of the `\input` file yourself. One way to do this is to write the complete path for the file after the `\input` command. Another way is to set the `TEXINPUTS` environment variable in your `.cshrc' or `.profile' file. The `TEXINPUTS` environment variable will tell TeX where to find the `texinfo.tex' file and any other file that you might want TeX to use.

Whether you use a `.cshrc' or `.profile' file depends on whether you use `csh`, `sh`, or `bash` for your shell command interpreter. When you use `csh`, it looks to the `.cshrc' file for initialization information, and when you use `sh` or `bash`, it looks to the `.profile' file.

In a `.cshrc' file, you could use the following `csh` command sequence:

```setenv TEXINPUTS .:/usr/me/mylib:/usr/lib/tex/macros
```

In a `.profile' file, you could use the following `sh` command sequence:

```TEXINPUTS=.:/usr/me/mylib:/usr/lib/tex/macros
export TEXINPUTS
```

This would cause TeX to look for `\input' file first in the current directory, indicated by the `.', then in a hypothetical user's `me/mylib' directory, and finally in the system library.