Dynamic Link Library

Most of us must have seen a few windows files with a dll extension, but did we care about what these files really are and what they actually do.
DLL(Dynamic Link Library) is a file consisting of number of functions that can be called by other programs running on the computer. DLL files that help in the operation of certain devices are known as the device drivers(These are the same files that are provided in a CD with your motherboard, the so called "driver CD").
DLL files help save memory as they are not loaded into the RAM along with the program making a call to it, rather it is loaded only when an explicit call is made to it. This property of DLL's help save the precious RAM memory. A DLL file simply acts as a repository of functions which can be used by a number of applications at the same time. Also the dll file is not compiled, only a reference is provided tothe dll file to use it.
A DLL file is often given a dll extension. A DLL file differs from an exe file as it can not be run directly, it must be called from other code that is already executing. In order to use a DLL file we have to register it by providng its references in the registry. To do this goto the command line(Start>run) and type in "regsvr32 filename.dll". This will register the dll file.
In order to open up a dll file you have to use a file named ILDASM.exe. This file can be found at "C:\Program Files\Microsoft.NET\FrameworkSDK\bin" if you have the .net framework installed.
So, now don't be puzzled in seeing all those dll files on your system and try checkingout a few of them.