  We have studied the dissolution of initially mass segregated and unsegregated
star clusters due to two-body relaxation in external tidal fields, using
Aarseth's collisional N-body code NBODY4 on GRAPE6 special-purpose computers.
When extrapolating results of initially not mass segregated models to globular
clusters, we obtain a correlation between the time until destruction and the
slope of the mass function, in the sense that globular clusters which are
closer to dissolution are more strongly depleted in low-mass stars. This
correlation fits observed mass functions of most globular clusters. The mass
functions of several globular clusters are however more strongly depleted in
low-mass stars than suggested by these models. Such strongly depleted mass
functions can be explained if globular clusters started initially mass
segregated. Primordial mass segregation also explains the correlation between
the slope of the stellar mass function and the cluster concentration which was
recently discovered by De Marchi et al. (2007). In this case, it is possible
that all globular clusters started with a mass function similar to that seen in
young open clusters in the present-day universe, at least for stars below m=0.8
Msun. This argues for a near universality of the mass function for different
star formation environments and metallicities in the range -2 < [Fe/H] < 0. We
finally describe a novel algorithm which can initialise stationary mass
segregated clusters with arbitrary density profile and amount of mass
segregation.
