Mention namespaces in step-20.

diff --git a/examples/step-20/step-20.cc b/examples/step-20/step-20.cc
index c1713c06e77a799f8be3b75e2ec34ec4aee84526..98d412490b0cb80ba0f9001a7bcba8df83f4591a 100644 (file)
--- a/examples/step-20/step-20.cc
+++ b/examples/step-20/step-20.cc
@@ -64,7 +64,8 @@
 // <code>TensorFunction</code> class that offers such functionality:
 #include <deal.II/base/tensor_function.h>
 
-// The last step is as in all previous programs:
+// The last step is as in all previous programs: We put all of the code relevant
+// to this program into a namespace. (This idea was first introduced in step-7.)
 namespace Step20
 {
   using namespace dealii;