Most people these days do their LATEXing in a graphical windowing editor with menus, running in a modern operating system that uses windows, icons, fonts, and a mouse which moves a pointer. This probably works fine 95% of the time, when you're dealing with one or two documents at a time, and everything you want to do is accessible through the menus, and you explicitly don’t want to see LATEX spilling its guts all over the place every time it reformats the document. Click here, move to there, cut, move somewhere else, paste, edit the text, write some more, click and you're done.
However, life isn’t always that easy. Sometimes things go wrong, and you need to open up the lid and find out what it was. This appendix is a short description of how to run LATEX manually, via the command-line, instead of through your editor, and it also covers error messages, and a few internal details about viewing and printing.
The editor wasn’t always the primary interface to TEX, except for actually writing and editing the document. Before graphical editors with built-in LATEX controls, you had to leave your editor, type a command to process your document, and another to view it or print it. For a small but significant number of people, running LATEX this way is still the order of the day.
Maybe they’re working on a giant mainframe or supercomputer console with no graphics, just a 3270 or VT-100 terminal like those in Figure C.1;
They might be using a smartphone where the editing facilities are limited and the scope for full menus entirely absent;
Perhaps they are simply uninterested in all the bells and whistles of the modern interface, with too many menus doing things they can actually work faster typing instructions by hand;
Possibly they’re using automation facilities that LATEX editors don’t have, like the ability to apply the same edit to thousands of documents while you go and have a coffee or get on with something else;
Or perhaps they are writing a system where LATEX is the embedded typesetter, so they’re actually working in a completely different scripting or programming language which does a lot of other things before calling on LATEX behind the scenes to do some typesetting.
Before I go any further I’m going to assume at this stage that you have typed a document (for example Figure 1.2), and that you have saved it in a plaintext file with a filetype of .tex and a name of your own choosing, following the rules in the sidebar ‘Picking suitable filenames’.