  The Crab pulsar belongs to one of the most studied stellar objects in the
sky. Since its accidental detection in 1968, its pulsed emission has been
observed throughout most of the electromagnetic spectrum. Although currently
one of more than 2000 known pulsars, its way of work has remained not
understood making the Crab pulsar an object of continuous studies and interest.
Referring to the pulsed emission of the Crab pulsar only at radio wavelengths,
it reveals a diversity of different phenomena. They range from deviations of
the predicted slowing down process of the pulsar with time (long time
phenomena) to an irregularity of its single pulse emission (short time
phenomena). Similar and different kinds of deviations are observed at other
wavelengths. Consequently, the Crab pulsar provides a large diversity of
different emission characteristics which have remained difficult to interpret
with a uniform theoretical approach including all observed properties. Since a
review of all currently examined properties of the Crab pulsar is beyond the
scope of this paper, its goal is to give an overview of previous studies of the
Crab pulsar predominantly at radio and gamma-wavelengths with an emphasis on a
possible connection to its radio single pulse emission. A discussion of a
possible identification of common emission mechanisms is given.
