Say a couple more things.

git-svn-id: https://svn.dealii.org/trunk@23313 0785d39b-7218-0410-832d-ea1e28bc413d

diff --git a/deal.II/examples/step-2/doc/intro.dox b/deal.II/examples/step-2/doc/intro.dox
index d12f73392ea8d35c79e96a5e9193d7559022ef0a..46cacf2709ee5bc8679c7198b998c3863b09827e 100644 (file)
--- a/deal.II/examples/step-2/doc/intro.dox
+++ b/deal.II/examples/step-2/doc/intro.dox
@@ -13,7 +13,14 @@ Defining degrees of freedom ("DoF"s in short) on a mesh is a rather
 simple task, since the library does all the work for you. Essentially,
 all you have to do is create a finite element object (from one of the
 many finite element classes deal.II already has, see for example the
-@ref fe documentation) and give it to a DoFHandler object.
+@ref fe documentation) and give it to a DoFHandler object through the
+DoFHandler::distribute_dofs function. The DoFHandler is a class that
+manages which degrees of freedom live where, i.e. it can answer
+questions like "how many degrees of freedom are there globally" and
+"on this cell, give me the global indices of the shape functions that
+live here". This is the sort of information you need when determining
+how big your system matrix should be, and when copying the
+contributions of a single cell into the global matrix.
 
 The next step would then be to compute a matrix and right hand side
 corresponding to a particular differential equation using this finite