use danish lang code, not country (#6909)

books/free-programming-books-da.md

@@ -0,0 +1,33 @@
+### Index
+
+* [C](#c)
+* [C#](#csharp)
+* [C++](#cpp)
+* [Java](#java)
+* [Pascal](#pascal)
+
+
+### C
+
+* [Beej's Guide til Netvarksprogrammierung](https://web.archive.org/web/20190701062226/http://artcreationforever.com/bgnet.html) - Brian "Beej Jorgensen" Hall, Art of Science (HTML) *(:card_file_box: archived)*
+* [Programmering i C](http://people.cs.aau.dk/~normark/c-prog-06/pdf/all.pdf) - Kurt Nørmark (PDF)
+
+
+### <a id="csharp"></a>C\#
+
+* [Object-oriented Programming in C#](http://people.cs.aau.dk/~normark/oop-csharp/pdf/all.pdf) - Kurt Nørmark (PDF)
+
+
+### <a id="cpp"></a>C++
+
+* [Notes about C++](http://people.cs.aau.dk/~normark/ap/index.html) - Kurt Nørmark (HTML)
+
+
+### Java
+
+* [Objektorienteret programmering i Java](http://javabog.dk) - Jacob Nordfalk
+
+
+### Pascal
+
+* [Programmering i Pascal](http://people.cs.aau.dk/~normark/all-basis-97.pdf) - Kurt Nørmark (PDF)