Editing TeX (section)

===How it is run===
[[File:LaTeX sample.png|thumb|A sample page produced using TeX with the [[LaTeX]] macros]]
A sample [[Hello world program]] in plain TeX is:

<syntaxhighlight lang="latex">
Hello, World
\bye          % marks the end of the file; not shown in the final output
</syntaxhighlight>

This might be in a file ''myfile.tex'', as ''.tex'' is a common [[file extension]] for plain TeX files. By default, everything that follows a percent sign on a line is a comment, ignored by TeX. Running TeX on this file (for example, by typing <kbd>tex&nbsp;myfile.tex</kbd> in a [[command-line interpreter]], or by calling it from a [[graphical user interface]]) will create an output file called ''myfile.dvi'', representing the content of the page in a '''d'''e'''v'''ice '''i'''ndependent format (DVI). A DVI file could then be either viewed on screen or converted to a suitable format for any of the various printers for which a device driver existed (printer support was generally not an operating system feature at the time that TeX was created). Knuth has said that there is nothing inherent in TeX that requires DVI as the output format, and later versions of TeX, notably pdfTeX, XeTeX, and LuaTeX, all support output directly to [[Portable Document Format|PDF]].