DYNAMIC LINK LIBRARY - DLL 

The DLL are files which can be called when required by the other program that is running in the computer. The DLL files which support the specific device operation are termed as device drivers. The benefit of the DLL files is that, space is saved in the RAM as they don't get loaded into the random access memory (RAM) together with the main program. For illustration, if a user is editing a document by using the Microsoft Word, the printer DLL file does not require to be loaded into the RAM. Whenever the user decides to print the document, after that the Word application causes the printer DLL file to be loaded and run. The DLL file is frequently given a ".dll" file name suffix. The DLL files are dynamically linked with the program which uses them during the program execution instead of than being compiled with the main program.