\documentclass[12pt]{article}
%\title{Package Test: algorithm/algorithmic}
\usepackage[english]{babel}
\usepackage[utf8x]{inputenc}
\usepackage{algorithm}
\usepackage{algorithmic}
\begin{document}
\begin{algorithmic}
\STATE $S \leftarrow 0$
\end{algorithmic}
\begin{algorithmic}
\IF{some condition is true}
\STATE do some processing
\ELSIF{some other condition is true}
\STATE do some different processing
\ELSIF{some even more bizarre condition is met}
\STATE do something else
\ELSE
\STATE do the default actions
\ENDIF
\end{algorithmic}
\end{document}
