Update free-programming-books.md

added "Deep C" under entry of C material.

free-programming-books.md

@@ -476,6 +476,7 @@
 * [The new C standard - an annotated reference](http://www.knosof.co.uk/cbook/cbook.html)
 * [Object Oriented Programming in C](http://www.planetpdf.com/codecuts/pdfs/ooc.pdf) (PDF)
 * [C Programming - Wikibooks](http://en.wikibooks.org/wiki/Programming:C)
+* [Deep C] (http://www.slideshare.net/olvemaudal/deep-c)
 
 
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