``Computers are stupid'', I still hear being said by childrens voices. And as so often, they are right. Computers are limited. You first have to tell them everything specificly, so that they do what they should be doing. However, as they are not (yet -TT) capable of understanding the human voice (let alone interpreting what you said), you must move to the level of the machine and command the computer with the keyboard what it has to do.
In the age of Mice and GUIs, the keyboard is moving more and more towards oblivion, when typing texts however, it is (fortunately) indispensable as yet. As you have to get the texts into the computer through use of the keyboard anyway, it is also practical to build the commands concerning which texts, how and where are to be placed on a page, into the text.
TEXfunctions the same way. You write a text, as you would do with a typewriter. Every time though, when you want to make something special – like for example printing a word bold or italicized – you have to tell the computer. This happens through the use of commands, that you build into the text right in front of it. How should a computer otherwise understand that a particular word should be printed in a bold typeface?
Though the computer knows how to handle the text, the characters on the screen or on harddisk are again Chinese for the printer. So, the text must be processed in a way that it will produce a good looking text from it. To this end you need the TEXprogram. The conversion is separated into two stages. The first stage is done by the program virtex (which means ``virgin'' TEX). It performs the conversions which are the same for every printer. As a result, it delivers a file, which ends with the suffix .dvi. The second stage is taken over by the printerdriver DVIprint, which completes the specific conversions for the printers connected. It takes the file ending in .dvi and sends the result of its conversion to the printer.
``Should this mean, that I have to compile (convert) every text twice first and even have to print it, before I can see what it looks like?''
Yes and no. Yes, because both of the conversions are always necessary. Without them, you cannot see, what became of the text-command-mix. No because, there is a possibility to convert the texts in a way that you can view them on screen.
To this end, the program with the name ShowDVI exists, which converts every file ending in .dvi and displays it on the screen. The second stage is thus different. ShowDVI does so to say not print out on paper, but to the screen. Without having to waste paper, you can preview this way, whether something became of the text. If it is according to your taste, you employ the DVIPrint program to print the document. Should changes be applied, both stages just have to be followed through again.
Summary To create a document with TEX, you have to
– type a text and intersperse it with commands convert this with the virtex program into a file, that ends with the suffix .dvi display this with the ShowDVI program on the screen and decide whether you like it if you don't, start again if you do, print it on the printer with DVIprint
To some, this method may not seem entirely modern. I dare to pose however, that I am considerably faster with this method than with a so called DTP program and that the printouts are aesthetically more pleasant.