  This paper presents new results from a photometric study of the main-sequence
stars in M4, the closest globular cluster to the sun. Multi-field, multi-epoch
observations at approximately 1, 2, and 6 core-radii were obtained with the
WFPC2 camera on the HST. The multi-epoch observations allowed us to clean the
data on the basis of proper motion. In all the fields the cluster main sequence
can be traced to at least V = 27.0 but there remains a trail of stars to the
limit of the data near V = 30 in the deepest outer field. There is no evidence
that we have reached the end of the hydrogen burning main sequence in any of
our fields, however, there is some indication that very few stars remain to be
detected in the deepest data.
  The scatter about the cluster main sequence yields a surprisingly small and
variable binary fraction; f_b = 2% in the inner parts of the cluster falling to
the 1% range outside. For the currently visible main sequence stars, the
cluster mass function is very flat (alpha =0.1) in the outer field and flattens
further in the inner fields suggesting well developed mass segregation. The
observed variation in the mass function is broadly consistent with isotropic,
multi-mass Michie-King models. Because we have a large sample of white dwarfs
in the outer field we are able to show that the cluster IMF above 0.8Msun was
considerably steeper than the present day mass function for low mass stars.
  Two appendicies are included in this contribution; a detailed discussion of
the techniques used to reduce the data and a direct comparison between the
cluster stars and those belonging to the inner spheroid of the Galaxy yielding
a Galactocentric distance of 7.5+/-0.6 kpc.

Astrophysics