14. Introduction to the LaTeX Document Preparation System

What will you do if your teacher asks you to prepare a project report using the PC? You will open Microsoft Office, type the document, and save it as a doc file. You will spend a good amount of time changing fonts, aligning the lines and in general trying to make the document look “beautiful”.

There are many problems with this approach to document preparation especially as you start writing lengthy (and technical) documents like scientific reports or books. It is a bit difficult at this point to explain what these problems are; we shall get into it later. The important thing is to realize that using a word processor like MS Office (or OpenOffice, on GNU/Linux) is not the only way to prepare documents. A far superior method is available; this involves using a program called LaTeX.

Note

We will make heavy use of the operating system terminal/command line as well as a text editor program like gedit in the remaining part of this book. So it is a good idea to review the material in Chapter 1 as well as Appendix 1 before proceeding further.

14.1. A Simple LaTeX document

Use your favourite text editor (say gedit) and create a text file containing the following lines:

\documentclass{article}
\title{Srinivasa Ramanujan}

\begin{document}

\maketitle

Srinivasa Ramanujan was an Indian mathematician and
self taught genius who, with almost no formal training
in pure mathematics, made substantial contributions to
mathematical analysis, number theory,
infinite series and continued fractions.

\end{document}

Save the file as ramanuja.tex; this is your report on Srinivasa Ramanuja, the famous Indian mathematician, which you are supposed to submit to your maths teacher tomorrow!

But wait, what are all those mysterious \documentclass, \title etc doing in the document?

The idea is that you can use a powerful program called LaTeX to convert this file into a very good looking document which can be printed on paper. How do we do this?

Open a terminal and type the following command:

pdflatex ramanuja.tex

“pdflatex” generates a new file “ramanuja.pdf” using the data contained in “ramanuja.tex”; you will see a lot of messages getting printed on the screen during this process - don’t worry about it as long as you get back the command prompt (in case there is some error, you will not get the command prompt - we will see how to handle this towards the end of this chapter).

A file with name ending in .pdf can be given directly to a printer or it can be viewed on the screen (on GNU/Linux) using one of two programs: either xpdf or evince. You simply have to give the command:

xpdf ramanuja.pdf

or:

evince ramanuja.pdf

at the operating system command line.

Here is what you will see when you print (or view) the PDF document:

Sometimes, your GNU/Linux installation may not have the command pdflatex installed. In that case, there is another way to generate printable output.

First, we run the command latex:

latex ramanuja.tex

This will generate a new file called “ramanuja.dvi”. You have to convert a .dvi file to either PDF or Postscript by using the commands dvipdf or dvips:

dvips ramanuja.dvi

will generate a new Postscript file called “ramanuja.ps” which can be directly printed or viewed on the screen using xpdf or evince.

If you wish to generate PDF output, you can try:

dvipdf ramanuja.dvi

14.2. What does LaTeX really do?

If you look at the PDF document produced by LaTeX, you will see that it does not contain any of the lines \documentclass, \title etc. Instead, what you see is neatly formatted output. The title has a bigger font size and is centralized. The left and right ends of all the lines are perfectly aligned; the word “continued” has been split to make the alignment perfect. Usually, when we prepare documents using MS-Word or OpenOffice, we spend a lot of time doing all these things manually - the problem with the approach is that as the document gets larger in size, we will be spending more and more time on this rather than concentrating on our writing. It’s here that LaTeX comes to our rescue. All the details involved in getting beautiful printed output is handled by LaTeX - we simply have to focus on our writing! This does not mean that we can simply type an article and expect LaTeX to format it properly. For example, how does LaTeX know what the title of the article is?

Simple. When you write a line like:

\title{Srinivasa Ramanujan}

you are telling LaTeX that “Srinivasa Ramanujan” is the title of the article. This does not result in the title being actually displayed - LaTeX simply notes down the fact that the title is “Srinivasa Ramanujan”. It is displayed when you type:

\maketitle

Because it is the title, LaTeX gives it a bigger font size and displays it at the center.

Now, how does LaTeX know what font size is to be used in the body? If you are preparing a document which is to be used as a presentation and projected onto a screen (say using an LCD projector), the fonts have to be much larger. This is where the “documentclass” becomes relevant. If you look at the kind of documents around you, you will see articles, books, letters, slides etc. Each “kind” of document has its own logical structure. A letter has a “From Address”, “To Address”, “Signature”, “Salutation”, “Subject”, “Place”, “Date” etc while an article does not have most of these. A book will have chapters, sections and sub-sections while an article won’t have chapters in it. Before you start writing the content of a LaTeX document, you must tell LaTeX what kind of document you are planning to write. That is what:

\documentclass{article}

does; you are telling LaTeX that what you are going to prepare is an article and NOT a slide or a book or a letter. Once you give this information to LaTeX, LaTeX will decide how your document is to be formatted.

Note

You can specify options to the \documentclass command; say you wish the font to be 12 point in size and the display be in two columns, you can write: \documentclass[twocolumn,12pt]{article}

Once you specify the document class and title, you can write the actual content of the document - this has to be written between the lines:

\begin{document}

and:

\end{document}

14.3. Sections and sub-sections

Create another text file, sample1.tex, with the following lines in it:

\documentclass {article}
\title{A sample document}
\author{Pramode C.E}
\date{23 Jan 2010}

\begin{document}

\maketitle

\section{This is a section}

Articles are usually organized as sections, sub-sections etc.

\subsection{This is a sub section}

A subsection is part of a section.

\section{This is another section}

This section does not have any sub-section!

\end{document}

This is how the generated pdf/postscript file looks:

The \title, \author and \date commands set a title, author and date for the document (current date is automatically used if date is not specified) - these are displayed only when \maketitle is invoked.

A new section is specified by writing:

\section{name of section}

LaTeX automatically numbers the section and chooses an appropriate font size. Likewise, a subsection is created by:

\subsection{name of sub-section}

Note that LaTeX again saves us the effort involved in section numbering and font size selection. LaTeX is also capable of automatically generating a table of contents for us using the section names specified!

14.4. Lists, Quotes and Quotations

Enter the following text into a file, say sample2.tex:

\documentclass {article}

\begin{document}

Here is how you typeset a short quotation:
\begin{quote}
This is an example of a short quotation. It consists of a single
para of text. See how it is formatted.
\end{quote}

And, here is an example of a longer quotation:
\begin{quotation}
This is an example of a longer quotation. It consists of more
than one paragraph of text.

This is the second para of the quotation.
\end{quotation}

Here is an example of an unnumbered list:
\begin{itemize}
 \item Apple
 \item Orange
 \item Banana
\end{itemize}

And, an example of a numbered list:
\begin{enumerate}
 \item Newton
 \item Pascal
 \item Euler
\end{enumerate}

\end{document}

Here is the PDF output produced by LaTeX:

A short quotation of only one paragraph can be formatted by enclosing it within:

\begin{quote}

and:

\end{quote}

The \begin command is said to introduce a LaTeX environment, the name of the environment is what is given in curly brackets. Note that LaTeX offsets the text within the quote a little bit to the right.

The quotation environment should be used for displaying longer (multiple paragraphs) quotations.

The itemize environment is used for displaying unnumbered lists. Each item in the list should be written like this:

\item name of item

If you want numbered list, you can use the enumerate environment.

14.5. Handling errors

Try this experiment: in sample2.tex, change:

\end{enumerate}

to:

\end{itemize}

and run pdflatex or latex once again. Instead of getting back the command prompt, you will see something like this:

! LaTeX Error: \begin{enumerate} on input line 27 ended by \end{itemize}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
...

l.31 \end{itemize}

?

The error occurs because a \begin{enumerate} should end with \end{enumerate}. You should type q to get back the command prompt and rectify the error.