• Most Microsoft Windows users are unaware that DLL files are working in the background, much less know that they do. Although they number in the thousands and errors relating to them are best left to a professional, it's a good idea for the average person to have a basic understanding of the purpose of some of the more important Windows DLL files and how they serve as co-pilots in the world of computing.
  
  

DLL Defined

• DLL is an acronym that stands for Dynamic Link Library. The term "dynamic link" is key since DLL files are not executable by the human user. Instead, they are called up by other code that is already running and treated like modules. In other words, they can't be run like a program can but are activated when an application or another DLL file needs them. While this may sound complicated, DLL files actually simplify things. Without these files, every application or interface would have to contain the same set of built-in instructions to perform the same common tasks, which would become very tedious for programmers. In contrast, the Windows operating system is designed to share these functions with multiple applications by making them available on demand from a library of files. In addition, the same DLL file can run in more than one application at the same time.
  
  

KERNEL32.DLL

• This file is used by Windows to manage memory. The name kernel is appropriate since this file is the core of the Windows operating system. The file loads into memory when the computer is started, and its first task is to protect the memory address page where a program or hardware device will save data for later retrieval. It also manages various other processes as the computer user runs and ends certain tasks, as well as responding to system shut-downs and interrupts.
  
  

USER32.DLL

• As the name implies, this file is involved in managing user interface functions and, as such, is linked to the User API Client Library, or user application programming interface. For instance, one of its tasks is to launch the desktop window. It is another core file that Windows depends on to work correctly. In fact, if it is damaged or missing, the operating system won't run at all.
  
  

GDI32.DLL

• This dynamic link file is specific to Window's graphics device interface, or GDI. Its purpose is to provide functions that allow programs and printers to display graphics and formatted fonts and text. It also enables programs to create, draw or modify graphics while managing graphic drivers to preserve resources.
  
  

COMDLG32.DLL

• This file manages dialog boxes that are central to the common file functions of all Windows applications. Examples of these functions include, New File, Open File and Save File.