\documentclass{book} 
\usepackage{algorithm}
\usepackage{algpseudocode} 
\begin{document}
\begin{algorithmic}[1]
\Procedure{Proc}{$a,b$}
\State\Return{7}
\EndProcedure
\end{algorithmic}

\begin{algorithm}
\caption{Euclid's algorithm}\label{euclid}
\begin{algorithmic}[1]
\Procedure{Euclid}{$a,b$}\Comment{The g.c.d. of a and b}
\State $r\gets a\bmod b$
\While{$r\not=0$}\Comment{We have the answer if r is 0}
\State $a\gets b$
\State $b\gets r$
\State $r\gets a\bmod b$
\EndWhile\label{euclidendwhile}
\State \textbf{return} $b$\Comment{The gcd is b}
\EndProcedure
\end{algorithmic}
\end{algorithm}
\end{document}
