An overview of the deal.II library is given. This library provides
the functionality needed by modern numerical software used in the finite
element solution of partial differential equations, offering adaptively
refined meshes, different finite element classes, multigrid solvers and
support for one, two and three spatial dimensions.
We give a description of the basic design criteria used in the
development of the library and how they were transformed into actual
code, and some examples of the use of the library in numerical
analysis.