December 13, 2001

DLL files, what the heck are they? Many people have heard me talk about problems with DLL files and probably wondered what they are and what they do. Again, I don't want to get too technical so we'll just scratch the surface and talk in generalities.

Well, DLL, or dynamic link library files, are a small application, or group of applications which a program uses to provide a service or set of data for the program. DLL files may only be used by one program, several, or all. The names of the files are hardly ever distinguishable as to what program they are associated with. Programmers like using DLL files because it is easier to write the code for programs when they can just call up a DLL rather than write extra code into the program and if a change is made, it is easier to change, or modify a DLL than it is to recompile the program itself.

DLL's also make the computer perform better since the stuff in them is not in memory until needed with the program so the computer can run more efficiently. They also allow the programs on the computer to interact with each other.

Enough for the plus side for the software manufacturers, now for the minus side for the end users. Let's assume I just wrote a program and most of the program runs fine with the common DLL files installed by Windows. Now let's say I add a feature which doesn't look or act exactly as I would like. Now I modify a DLL file to make my application perform great, so when someone purchases my program and installs it on their computer, the installation routine replaces the original Windows DLL with my modified version. Now let's also assume during my beta testing, nobody used a particular program made by a competitor, or for that matter, a Windows core program which is seldom used. Now, when someone runs that program, the screen doesn't look correct, the dreaded "blue screen of death" pops up, or the famous "you performed an illegal operation and this program will shutdown" happens.

So now, the computer guy comes to your house when your printer is acting strange and spends countless hours trying to straighten out the problem, and after reinstalling half of the software on the computer, it is OK again, or "heaven forbid", he says "since the problem is minor, it isn't worth the time it'll take to redo everything so it would be better to just live with it", now that one little modified DLL file has turned your computer into a monster.

DLL's are also a target of some viruses since they can really cause problems and be difficult to locate when infecting these files. Again, I can't stress enough, KEEP YOUR VIRUS DEFINITIONS UP TO DATE! This has been a crash course in DLL stuff but at least now you can understand the principals and understand why sometimes they can also make it tough to keep your computer running smoothly. Sometimes when you remove a program, the modified files are left behind and affect the performance of the computer and software. That's why someone who loads and removes a lot of programs can benefit from reformatting and reinstalling once in a while.

If you have any questions or comments, please