.DLL File Extension

A dynamic link library (DLL) is a collection of small programs, which can be called upon when needed by the executable program (EXE) that is running.

The Compiled library files are  containing a set of  drivers and/or procedures that are referenced and executed by a program that allows multiple programs to access shared system functions through common libraries and It may be dynamically linked into a program at runtime.

Most of the  DLL files are provided with the Windows operating system, and others are included by Windows programs and they allow various program functions, such as communication with external devices and hard disk input and output and it can be referenced by Mac cross-platform applications.

An example : If the program (exe) needs to get the free space of your hard drive. It can call the DLL file that contains the function with parameters and a call function. The DLL will then tell the executable the free space. This allows the executable to be smaller in size and  haven’t to write the function that has already exists.

COMDLG32.DLL

It controls the dialog boxes.

GDI32.DLL

It contains numerous functions for displaying text, managing fonts and drawing graphics.

KERNEL32.DLL

It contains hundreds of functions for the memory management and various processes.

USER32.DLL

It contains numerous user interface functions. It involved in the creation of program windows and their interactions with each other.

NOTE: The contents of a DLL file may cause errors within the program that references the file when deleting or modifying; for this reason, DLL files generally should not be opened or edited.  See here – “How to Open a dll file ?“