  In this paper, we are interested in the number of fixed points of functions
$f:A^n\to A^n$ over a finite alphabet $A$ defined on a given signed digraph
$D$. We first use techniques from network coding to derive some lower bounds on
the number of fixed points that only depends on $D$. We then discover
relationships between the number of fixed points of $f$ and problems in coding
theory, especially the design of codes for the asymmetric channel. Using these
relationships, we derive upper and lower bounds on the number of fixed points,
which significantly improve those given in the literature. We also unveil some
interesting behaviour of the number of fixed points of functions with a given
signed digraph when the alphabet varies. We finally prove that signed digraphs
with more (disjoint) positive cycles actually do not necessarily have functions
with more fixed points.
