DLL Files 101 – DLL File Fundamentals, Part I
What is a DLL File?
The letters in the abbreviation “DLL” stand for “Dynamic Link Library”. A DLL File is a library of various procedures that a program can call upon when needed. A DLL file is loaded and linked to a specific executable program anytime that program is run. Programs call upon DLL files in order to receive instructions needed to perform certain operations.
In less layman terms: a DLL file is a dynamically-loaded, external code repository. What this means is that the data contained in the file is neither immediately bound to any particular executable program nor copied into one at compile time when the program is created, rather remaining in a separate disk where it remains until being loaded at run-time or execution by any of the potentially numerous programs to which it corresponds.
One DLL File – Multiple Programs
In order to dramatically preserve storage space and prevent potential confusion in the system, a single DLL file may be linked to multiple programs, as oftentimes multiple programs may share certain abilities that are programmed into one particular DLL file. As such, DLL files may also be used to integrate multiple programs.
What Kind of Instructions Do DLL Files Contain?
DLL files quite often involve the distribution of memory, disk space, and hardware resources though they can provide instructions on almost any routine action a program performs. For example, a DLL file can instruct a program on how to:
• Search for free space on the hard drive
• Print to the default printer a sample (or “Preview”) page of what’s currently on the display screen
• Find a file a certain directory
How Are DLL Files Stored?
DLL files are stored on your PC’s hard drive, usually in the Windows Registry. Any file that ends with the “.DLL” file extension is a DLL file.
A DLL file loads on demand at run-time whenever a program to which it is linked is started. The program requests the DLL file of your PC’s operating system, and the OS makes sure the appropriate one is loaded. Otherwise, the DLL file just sits dormant in the hard disk, saving your PC’s precious memory space for more vital and present functions. When the program no longer requires the services the given DLL file provides, that DLL is then unloaded.
Usually, similar or related functions are grouped together in the same Dynamic Link Library. This is designed to make it as fast, easy, and efficient as possible for your PC to access the instructions one or more programs currently running need to perform their respective duties.
More on DLL File Fundamentals
To find out more about DLL files, including:
• The difference between DLL files and Windows Registry files
• Why DLL files exist
• And the why it’s so important for every PC-user to understand DLL files
please check out the second part of this two-part primer on DLL File Fundamentals – DLL Files 102.