DLL stands for Dynamically Linked Library. A DLL file is one that is usually associated with an executable file (.exe). A DLL is a library that contains code and data information for certain operating systems which makes it easier for program files to be installed. For example in a windows operating system, the DLL comdlg performs common dialogue box related functions. Every installing program can tap into the DLL and use the functionality contained in it. This way it doesn’t need to store those extra details in the program files. It just needs to contain a module to connect to the DLL resources. This saves a lot of space as it reduces the program bulk drastically.
Some DLL’s reduce the file encoding from dll-files download about 30 lines to 3 lines. The program thus becomes space effective along with enhanced performance and increased capabilities. By using a DLL file, programs can thus be modularized and segregated into different components. Each module can be loaded onto the run time whenever required during the installation. Since each module is separated the run time becomes much faster as the modules are only loaded as and when they are required. The program can gloss over the modules whose functionality is not requested. Additionally, the update installment also becomes much faster as only the modules whose updates need to be changed are accessed without affecting the rest of the program.
Some of the major DLL files implemented in Windows Operating Systems are:
ActiveX Controls (.ocx) files such as calendar controls
Control Panel (.cpl) files, which are located in the control panel and each item is a specialized DLL
Device Driver (.drv) files, which connect to external devices such as printers etc.