maxima lisp emacs



Hi,

When I use Lisp command :
(format st "/* XPM */~%static char *mandelbrot[] = {~%")

( it is from file : complex_dynamics.lisp)

Emacs gives :
EVAL: variable ST has no value
    [Condition of type SYSTEM::SIM

What means st here ?
It is not a part of  Lisp ?

Regards

Adam