It states- A DLL is a library that contains code and data that can be used by more than one program at the same time
. For example, in Windows operating systems, the Comdlg32 DLL performs common dialog box related functions. Therefore, each program can use the functionality that is contained in this DLL to implement an Open dialog box. This helps promote code reuse and efficient memory usage.
Precisely, a dynamic link library (DLL) is a combination of very small codes and programs that can be called upon when required by the concerned executable program (.exe) that is running currently. These DLL allow the particular exe communicate with any specific device such as a mouse, keyboard or printer or may contain source code to perform particular functions.
I would like to mention few important DLL files here.
1.COMDLG32.DLL It Controls the dialog boxes used by Windows applications.
2.GDI32.DLL- Contains numerous codes and functions for GDI drawing graphics, displaying text, and managing fonts. Helps creating windows simple two dimensional objects.
3.KERNEL32.DLL-very important and contains hundreds of functions for the management of memory and various processes.
4.USER32.DLL- Contains numerous user interface functions. Involved in the creation of program windows and their interactions with each other.
The DLL files in windows operating system reside under system32 folder (under system in me). Whenever you receive any DLL file missing error message this means the respective DLL is missing from aforementioned location and you need to re-save it right there for its normal functionality. Any DLL file can be found online now a days easily and just copying and pasting it there in system32 folder will work most of the time.