  This paper addresses the mutual visibility problem for a set of
semi-synchronous, opaque robots occupying distinct positions in the Euclidean
plane. Since robots are opaque, if three robots lie on a line, the middle robot
obstructs the visions of the two other robots. The mutual visibility problem
asks the robots to coordinate their movements to form a configuration, within
finite time and without collision, in which no three robots are collinear.
Robots are endowed with a constant bits of persistent memory. In this work, we
consider the FSTATE computational model in which the persistent memory is used
by the robots only to remember their previous internal states. Except from this
persistent memory, robots are oblivious i.e., they do not carry forward any
other information from their previous computational cycles. The paper presents
a distributed algorithm to solve the mutual visibility problem for a set of
semi-synchronous robots using only 1 bit of persistent memory. The proposed
algorithm does not impose any other restriction on the capability of the robots
and guarantees collision-free movements for the robots.
