 far, we have used Maxima in the interactive mode, rather like a
calculator.  However, for computations which involve a repetitive
sequence of commands, it is better to execute a program.  Here we
present a short sample program to calculate the critical points of a
function <tt>f</tt> of two variables <tt>x</tt> and <tt>y</tt>.  The program
cues the user to enter the function <tt>f</tt>, then it computes the
partial derivatives <tt>f</tt><sub><tt>x</tt></sub> and <tt>f</tt><sub><tt>y</tt></sub>, and then it