  In this paper, we propose a review of the free boundary formulation for BVPs
defined on semi-infinite intervals. The main idea and theorem are illustrated,
for the reader convenience, by using a class of second-order BVPs. Moreover, we
are able to show the effectiveness of the proposed approach using two examples
where the exact solution both for the BVPs and their \FBF \ are available.
Then, we describe the free boundary formulation for a general class of BVPs
governed by an $n$-order differential equation. In this context, we report
three problems solved using the free boundary formulation. The reported
numerical results, obtained by the iterative transformation method or Keller's
second-order finite difference method, are found to be in very good agreement
with those available in the literature. The last result of this research is
that, in order to orient the interested reader, we provide an extensive
bibliography. Of course, we may aspect further and more interesting
applications of the free boundary formulation in the future.
