  This paper deals with the dispersionless KP hierarchy from the point of view
of quasi-classical limit. Its Lax formalism, W-infinity symmetries and general
solutions are shown to be reproduced from their counterparts in the KP
hierarchy in the limit of $\hbar \to 0$. Free fermions and bosonized vertex
operators play a key role in the description of W-infinity symmetries and
general solutions, which is technically very similar to a recent free fermion
formalism of $c=1$ matrix models.
