There are lots of books on the subject but all give theoratical information. I want to learn implementation by examples. Is there any book/tutorial/article that explains implementation of CODECS using some programming langauge such as C?
Codecs are algorithms, so as such they are completely independent of a programming language.
That said, there are plenty of open source codecs implemented in C that you can learn from. For example, take a look at the libavcodec library which has a large variety of codecs, some very complex, and some not so much.
I believe to make sense of the code you will need to have an understanding of the algorithm behind it, so I recommend that whichever codec you decide to study you also obtain its formal specification.