A TEX input file is a standard Macintosh text file.
We won't create an input file from scratch, instead we'll use one
of the sample files provided in the TeX-docs folder.
There is nothing special about this folder, or LaTeX-docs.
I simply like to keep my TEX and LATEX input files in separate folders.
You can keep your input files anywhere you like.
The file we'll use is called nasty.tex.
As the name suggests, it is not a typical TEX input file,
but it does illustrate most of the things you'll encounter when using
in the future.
Switch to your text editor and open nasty.tex from the TeX-docs folder.
The only change we'll make to nasty.tex is to add a deliberate error:
insert the illegal command \xxx at the start of the file.
Save this change before switching back to .