Dynamic Link Library (DLL) is a very useful feature in Symbian C++ as it provides to us its code and data to used in one or more programs at the same time. It provides us a shared library whose methods can be used in our applications by importing and help us by not making us to create those classes from scratch. It accomplishes the task of reusability. The libraries generally have file extention like .DLL, .OCX, .DRV.
This article has abstractly presented us the concept of DLL and various types of DLLS in Symbian OS (i.e. Static interface DLL and Polymorphic interface DLL). The article is help to beginners only.
A basic explanation of DLL (static and polymorphic) is very useful to understand the concept of DLL. How DLL is loaded in memory and how it promote code reuse is explained in efficient way. Although beginners may find it hard to digest, this article is very useful to learn about DLLs in symbian.
Also note that one line paragraph "Alternative to Polymorphic Interface DLLs" is really important. I will prefer to use ECOM Plugin instead of polymorphic dll, as writing an ECOM Plugin is far more simple than writing a polymorphic dll.