DLL, Dynamic Link Library (.dll)
The DLL System file format
DLL, which is also known as Dynamic Link Library, is the implementation of the shared library concept by Microsoft in Microsoft Windows as well as OS/2 operating systems. DLL files should not be opened or edited since even slight changes of the contents can cause severe errors within the referenced program. If the DLL file of a program is missing or corrupted, installing a new version of the file is the best solution to get the program or application running again.
Technical details of DLL files
The libraries generally have the file extension DLL, DRV (for legacy system drivers) or OCX (for libraries that incorporates ActiveX controls). The file formats for DLLs are Portable Executable (PE) for 32 bit as well as 64 bit Windows, and New Executable (NE) for 16 bit Windows. DLL files can contain code, resources, and data. Data files with the same file format as DLL but with a different file extension, possibly containing only resource sections, are called resource DLLs.