LaTeX is a typesetting program that produces excellently typeset documents. Typesetting is placing text onto a page with all the style formatting defined, so that content looks as intended. It is extensively used for producing high quality scientific and mathematical documents. It is also used for producing other kinds of documents, ranging from simple one page articles or letters to books. LaTeX is based on the TeX typesetting language. 

~~~

TeX is a typesetting system designed and developed by Donald E. Knuth, the renowned Computer Scientist and Emeritus professor at Stanford University.

TeX is well known for it's stability and portability. TeX is known to be virtually bug free. 

~~~~~

LaTeX is an extension of TeX, consisting of TeX macros and a program to parse the LaTeX files. It is supposed to be an easier to use language than TeX, but producing the same quality of output. It was developed by Leslie Lamport in the early 1980s and is now being maintained and developed by the LaTeX3 Project.

Why should you use it?

~~~~~~~~~~~~~~~~~~~~~~

A few reasons for using LaTeX - 

  * It produces documents with excellent visual quality. 

  * It does the typesetting for you, leaving you - the author - to focus on writing the content.

  * It makes writing math just as easy as writing simple text.

  * It's renowned for it's stability and a virtually bug free code base. 

  * It uses plain text files as input and can give output in a variety of formats including PDFs and html making it platform independent.

  * It is widely used and has a large user community. 

First Document

--------------

Let's begin by writing a simple LaTeX, Hello World, document. The following code is typed out into a text editor. 

  %hello.tex - The Hello World of LaTeX

~~~~~~~~~~~~~~~~~~

What does it mean? - Understanding the source

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  The first line is a comment. It is meant only for human readers and LaTeX simply ignores that line. Anything following a ``%`` symbol, until the end of the line, is ignored by LaTeX. 

  This line is a command and sets the ``documentclass`` of the document to ``article``. LaTeX has other classes like ``report``, ``book``, ``letter``, etc. The typesetting of the document varies, depending on the ``documentclass`` of the document. 

  This line informs LaTeX that this is the beginning of the content of the document. The command, technically speaking, marks the beginning of the ``document`` environment. 

  The end command marks the end of the ``document`` environment. It tells LaTeX that the document is complete and LaTeX will simply ignore anything written after this line.

In order to explicitly instruct LaTeX to start a new-line, ``\\`` or ``\newline`` command is used. Appending ``*`` to ``\\``,  instructs LaTeX to create a new line, without creating a new page at that point. 

As already mentioned, ``%`` symbol marks the beginning of a comment. How would we then use it in our document's text? ``%`` is one of the many special characters and is used by escaping it with a backslash, as shown. Other special characters are  ``~ # $ ^ & _ { } \``. All of them, except the backslash character, can be inserted in the document by escaping them with a ``\`` character. To insert the ``\`` character, ``\textbackslash`` must be used. 

::

  %hello.tex - First LaTeX document

  \documentclass{article}

  \begin{document}

  Hello,       World!

  This will not start a new line. 

  But, this will start a new paragraph. 

  Again no new line. \% what follows isn't a comment. 

  \end{document}

  This is text that is ignored. 

Basic Structure

---------------

As already stated, the ``documentclass`` command tells LaTeX, the type of the document that you intend to create. Each class has a few differences in how the content of the document is typeset. 

Some of the available LaTeX classes are, article, proc, report, book, slides, letter. 

The information about the document such as it's title, the date, the author(s) information etc, is collectively known as the topmatter. The term topmatter is frequently used in LaTeX documentation. 

Let us add top matter to our document, now. 

To put a specific date, you can specify it as below

:: 

  \date{June 1, 2010}

These details do not appear in the document until we use the ``\maketitle`` command with the document environment to instruct LaTeX to place the top matter information into the document. 

Sectioning Commands

~~~~~~~~~~~~~~~~~~~

Documents are often divided into parts, chapters, sections and subsections. LaTeX provides an intuitive mechanism to use them in your documents. 

+-------------------+-------+------------------------+

| command           | level | comments               |

+-------------------+-------+------------------------+

| ``part``          |    -1 | not in letters         |

+-------------------+-------+------------------------+

| ``chapter``       |     0 | only books and reports |

+-------------------+-------+------------------------+

| ``section``       |     1 | not in letters         |

+-------------------+-------+------------------------+

| ``subsection``    |     2 | not in letters         |

+-------------------+-------+------------------------+

| ``subsubsection`` |     3 | not in letters         |

+-------------------+-------+------------------------+

| ``paragraph``     |     4 | not in letters         |

+-------------------+-------+------------------------+

| ``subparagraph``  |     5 | not in letters         |

+-------------------+-------+------------------------+

LaTeX has seven levels of sectioning commands, as shown above. 

Text of a block or a section of the document need not be enclosed within ``\begin`` and ``\end`` commands. LaTeX starts a new block each time it finds a sectioning command. 

  \section[Short Title]{This is a very long title and the Short Title will appear in the Table of Contents.}

The short title appears in the table of contents, if at all one is generated. 

Section Numbering

+++++++++++++++++

As you may have observed, numbering is done automatically in LaTeX. Parts are numbered using roman numerals; Chapters and sections are numbered using decimal numbers. When a table of contents is inserted into the document, all the numbered headings automatically appear in it.

A sectioning command appended with an asterisk gives an unnumbered heading that is not included in the table of contents.

::

  \section*{Introduction}

By default, levels up to 2, are numbered, i.e, parts, chapters, sections and subsections. This can be changed by setting the ``secnumdepth`` counter using the ``\setcounter`` command. The following command removes numbering of the subsections. Only parts, chapters and sections will be numbered. 

::

  \setcounter{secnumdepth}{1}

LaTeX allows for separate numbering for appendices. ``\appendix`` command indicates that the sections following it, are to be included in the appendix. 

Abstract

~~~~~~~~

LaTeX provides an ``abstract`` environment, to place an abstract in a document. The abstract appears in the document after the topmatter but before the main body of the document. 

::

  \begin{abstract}

    The abstract abstract.

  \end{abstract}

By default LaTeX uses the word "Abstract" as a title for the abstract. This can be changed using the ``\renewcommand``. 

::

  \renewcommand{\abstractname}{Summary}

Parts, chapters or sections that have been auto numbered by LaTeX automatically appear in the Table of Contents (ToC). ``\tableofcontents`` command places the ToC at the location, where the command has been issued. 

  \section*{Preface}

  \addcontentsline{toc}{section}{Preface}

Typesetting Text

----------------

Text formatting

~~~~~~~~~~~~~~~

Font Styles and Size

++++++++++++++++++++

LaTeX has three font families:

 1. roman ``\textrm{your text here}``

 2. serif ``\textsf{your text here}``

 3. monospace ``\texttt{your text here}``

For emphasizing text, *italics* are generally used. The ``\emph`` command is used to emphasize text. 

``\textbf`` gives  **bold face** text. Underlines can be made using the ``\uline`` command and ``\sout`` strikes out text. For small caps, ``\textsc`` command is to be used. 

LaTeX provides a series of commands to change the size of text. The table below shows the commands and the size of text, they produce. 

+-------------------+----------------+-------------+-------------+

| size              | 10pt (default) | 11pt option | 12pt option |

+===================+================+=============+=============+

| ``\tiny``         | 5pt            | 6pt         | 6pt         |

+-------------------+----------------+-------------+-------------+

| ``\scriptsize``   | 7pt            | 8pt         | 8pt         |

+-------------------+----------------+-------------+-------------+

| ``\footnotesize`` | 8pt            | 9pt         | 10pt        |

+-------------------+----------------+-------------+-------------+

| ``\small``        | 9pt            | 10pt        | 11pt        |

+-------------------+----------------+-------------+-------------+

| ``\normalsize``   | 10pt           | 11pt        | 12pt        |

+-------------------+----------------+-------------+-------------+

| ``\large``        | 12pt           | 12pt        | 14pt        |

+-------------------+----------------+-------------+-------------+

| ``\Large``        | 14pt           | 14pt        | 17pt        |

+-------------------+----------------+-------------+-------------+

| ``\LARGE``        | 17pt           | 17pt        | 20pt        |

+-------------------+----------------+-------------+-------------+

| ``\huge``         | 20pt           | 20pt        | 25pt        |

+-------------------+----------------+-------------+-------------+

| ``\Huge``         | 25pt           | 25pt        | 25pt        |

+-------------------+----------------+-------------+-------------+

Superscript and Subscript

+++++++++++++++++++++++++

For superscripting text in the text mode, LaTeX provides the ``\textsuperscript`` command. 

  This is how you super\textsuperscript{script} text. 

LaTeX does not provide any command for subscripting text in the text mode. The math mode needs to be used to obtain subscripts. 

  This is sub_{script}

+++++++++++++++

++++++++++++++++++

Lists - Itemize, Enumerate, and Description

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Special Paragraphs

~~~~~~~~~~~~~~~~~~

Footnotes

+++++++++

With the command::

  \footnote{footnote text}

a footnote is printed at the foot of the current page. Footnotes should always be put after the word or sentence they refer to. Footnotes referring to a sentence or part of it should therefore be put after the comma or period.

Quotes

++++++

++++++++

Including Code

++++++++++++++

The ``listings`` package can be used to embed source code into your LaTeX document. We shall briefly explore inserting python code into our document. 

Obviously, you first need to tell LaTeX that you want it to use the ``listings`` package, using the ``\usepackage`` command. 

::

  \usepackage{listings}

Then, we tell LaTeX that we are going to embed Python code into this document. A simple code highlighting for Python code can be achieved using this. 

::

  \lstset{language=Python,

          showstringspaces=false,

         }

You might want to customize the code highlighting further using other variables like ``basicstyle``, ``commentstyle``, ``stringstyle``, ``keywordstyle`` etc. For detailed information on all this, you should look at the ``listings`` package documentation. 

You include a block of code into your document by enclosing it within the ``lstlisting`` environment. 

::

  \begin{lstlisting}

  string="Hello, World! "

  for i in range(10):

      print string*i

  \end{lstlisting} 

You can also include source code files directly into your latex document, using the ``lstinputlisting`` command. 

::

  \lstinputlisting[lastline=20]{lstexample.py}

This command includes the first 20 lines of the file ``lstexample.py`` into out LaTeX document. 

Tables, Figures, Floats, & Referencing

---------------------------------------------

Tables

~~~~~~

The ``tabular`` environment allows typesetting tables in LaTeX. Like any other environment it starts with ``\begin`` command and ends with ``\end``. 

It takes an optional argument, ``pos`` that specifies the vertical position of the table relative to the baseline of the surroundging text. It takes values of ``t`` for top, ``b`` for bottom, or ``c`` for center. 

The ``col fmt`` argument specifies the formatting of the columns of the table. Following are the possible arguments to the tabular environment. 

Each row in a table is separated by ``\\`` command and each column entry of a row is separated by ``&``.