  The paper presents a method to compute the Jacobi's elliptic function
\texttt{sn} on the period parallelogram. For fixed $m$ it requires first to
compute the complete elliptic integrals $K=K(m)$ and $K'=K(1-m).$ The Newton
method is used to compute sn(z,m), when $z\in [0,K]\cup[0,i K').$ The
computation in any other point does not require the usage of any numerical
procedure, it is done only with the help of the properties of sn.
