  We use N-body integration to follow the evolution of clusters of 200 binary
systems with different initial half mass radii $R_{0.5}$. We also simulate
single-star clusters. All clusters evolve according to the same $n(t)$ curve,
where $n(t)$ is the number density of stars in the central 2~pc sphere at time
$t$. $n(t)$ and the lifetime are independent of (i) the inital proportion of
binaries and (ii) the initial $R_{0.5}$. Mass segregation measures the
dynamical age of the cluster. The proportion of binaries in the central cluster
region is a sensitive indicator of the initial cluster concentration. If most
stars form in binaries in a typical embedded cluster which is located at the
edge of a giant molecular cloud, then we estimate that at most about 10~per
cent of all pre-main sequence stars achieve near escape velocities from the
molecular cloud. The large ejection velocities resulting from close encounters
between binary systems imply a `halo' distribution of young stars over large
areas surrounding star forming sites which is expected to have a significantly
reduced binary proportion and a significantly increased proportion of stars
with depleted circumstellar disks. We compare the time dependent model single
star and system luminosity function in the central cluster region with the
observational Hyades and Pleiades luminosity functions and find no evidence for
different dynamical properties of stellar systems at birth in the Hyades,
Pleiades and Galactic field stellar samples. The observed proportion of binary
stars in the very young Trapezium Cluster is consistent with the early
dynamical evolution of a cluster with a very high initial stellar number
density.
