% Free sample LaTeX file from 99helpers.com/file-types/tex
% Build it with:  pdflatex sample-article.tex  (run it twice, see comment 9)
% A % sign starts a comment: everything after it on the line is ignored.

% 1. The document class: article, on A4 paper, 11 pt body text.
\documentclass[a4paper,11pt]{article}

% 2. The preamble: packages that add features, loaded before the text.
\usepackage[utf8]{inputenc}     % read the file as UTF-8 (default since 2018)
\usepackage[margin=25mm]{geometry}
\usepackage{amsmath}            % equation environments such as align
\usepackage{booktabs}           % proper rules for tables
\usepackage{tikz}               % drawing pictures with code
\usetikzlibrary{positioning}    % placement such as right=of
\usepackage{microtype}          % finer spacing and fewer bad line breaks
\usepackage[hidelinks]{hyperref}% clickable links and PDF bookmarks; load last

% 3. Metadata: used by \maketitle and stored in the PDF by hyperref.
\title{A Sample \LaTeX{} Article}
\author{Ada Example}
\date{27 October 2026\\[4pt]\small Free sample from 99helpers.com/file-types/tex}
\hypersetup{
  pdftitle={A Sample LaTeX Article},
  pdfauthor={Ada Example},
  pdfsubject={Free sample LaTeX file from 99helpers.com/file-types/tex},
}

% 4. A macro of your own: \file{name} sets a file name in typewriter type.
\newcommand{\file}[1]{\texttt{#1}}

\begin{document}
\maketitle

\begin{abstract}
This article is a sample \LaTeX{} source file. It shows the parts most
documents use: sections, mathematics, a table, a figure drawn with Ti\emph{k}Z,
cross-references and a bibliography. Read the source next to the PDF to see
which commands produced what.
\end{abstract}

% 5. Sections are numbered automatically; \label names them for references.
\section{Introduction}\label{sec:intro}
\TeX{} was written by Donald Knuth to typeset mathematics well~\cite{knuth84}.
\LaTeX{} adds commands for structure, so authors mark up \emph{what} each
part is and the class decides how it looks~\cite{lamport94}. Section~\ref{sec:maths}
shows some mathematics, Table~\ref{tab:engines} compares engines and
Figure~\ref{fig:cycle} shows the build cycle.

\section{Mathematics}\label{sec:maths}
% 6. Maths: $...$ inside a line, equation and align environments on their own.
Inline maths sits in the text, like $e^{i\pi} + 1 = 0$ or
$\sum_{k=1}^{n} k = \frac{n(n+1)}{2}$. Displayed equations get a number:
\begin{equation}\label{eq:gauss}
  \int_{-\infty}^{\infty} e^{-x^2}\,\mathrm{d}x = \sqrt{\pi}.
\end{equation}
The \file{align} environment lines up several equations at the \verb|&|:
\begin{align}
  (a+b)^2 &= a^2 + 2ab + b^2, \label{eq:square}\\
  \nabla \cdot \mathbf{E} &= \frac{\rho}{\varepsilon_0}.
\end{align}
Equation~\eqref{eq:gauss} is the Gaussian integral; \eqref{eq:square}
expands a square.

\section{A table}
% 7. A floating table: LaTeX places it where it fits, often at the top of a page.
\begin{table}[htbp]
  \centering
  \caption{Three common \TeX{} engines}\label{tab:engines}
  \begin{tabular}{@{}lll@{}}
    \toprule
    Engine   & Output & Fonts \\
    \midrule
    pdf\TeX  & PDF    & Type~1, 8-bit encodings \\
    Xe\TeX   & PDF    & System OpenType and TrueType, Unicode \\
    Lua\TeX  & PDF    & OpenType, Unicode, scriptable in Lua \\
    \bottomrule
  \end{tabular}
\end{table}

\section{A figure}
Figure~\ref{fig:cycle} has no image file: it is drawn by Ti\emph{k}Z
commands in the source, so it stays sharp at any zoom.

% 8. A figure drawn with TikZ: no image file, the picture is code.
\begin{figure}[ht]
  \centering
  \begin{tikzpicture}[
      box/.style={draw, rounded corners, minimum width=24mm,
                  minimum height=9mm, font=\small},
      >=stealth, node distance=8mm]
    \node[box] (tex) {\file{article.tex}};
    \node[box, right=of tex] (engine) {pdflatex};
    \node[box, right=of engine] (pdf) {\file{article.pdf}};
    \node[box, below=of engine] (aux) {\file{.aux .log .toc}};
    \draw[->] (tex) -- (engine);
    \draw[->] (engine) -- (pdf);
    \draw[->] (engine.south west) to[bend right=20] (aux.north west);
    \draw[->] (aux.north east) to[bend right=20]
      node[right, font=\footnotesize] {next run} (engine.south east);
  \end{tikzpicture}
  \caption{The build cycle: each run writes auxiliary files that the next run reads.}
  \label{fig:cycle}
\end{figure}

% 9. Cross-references: \ref and \cite are resolved from the .aux file,
%    so the first run prints ?? and a second run fills in the numbers.
\section{Building this file}
Run \file{pdflatex} twice. The first run writes labels and citations to
\file{sample-article.aux}; the second reads them back, which is how
Section~\ref{sec:intro} and page~\pageref{fig:cycle} get their numbers.

% 10. The bibliography: thebibliography needs no BibTeX run.
\begin{thebibliography}{9}
\bibitem{knuth84}
  Donald E. Knuth. \emph{The \TeX book}. Addison-Wesley, 1984.
\bibitem{lamport94}
  Leslie Lamport. \emph{\LaTeX: A Document Preparation System}.
  2nd edition, Addison-Wesley, 1994.
\end{thebibliography}

\end{document}