\documentclass[12pt]{article}
\usepackage[a5paper]{geometry}
\title{algorithmicx (algpseudocode) example}
% From the package documentation:
% "The package algorithmicx itself doesn’t define any
% algorithmic commands, but gives a set of macros to
% define such a command set. You may use only
% algorithmicx, and define the commands yourself, or you
% may use one of the predefined command sets."
%
% Popular predefined command sets include algpseudocode and algpascal. algcompatible should only be used in old documents, and algc is incomplete.
\usepackage{algpseudocode}
\begin{document}
\begin{algorithmic}
\Require $n \geq 0$
\Ensure $y = x^n$
\State $y \Leftarrow 1$
\State $X \Leftarrow x$
\State $N \Leftarrow n$
\While{$N \neq 0$}
\If{$N$ is even}
\State $X \Leftarrow X \times X$
\State $N \Leftarrow \frac{N}{2} $ \Comment{This is a comment}
\ElsIf{$N$ is odd}
\State $y \Leftarrow y \times X$
\State $N \Leftarrow N - 1$
\EndIf
\EndWhile
\end{algorithmic}
\end{document}
