1 00:00:00,000 --> 00:00:04,640 Anyone who's used Windows, especially older versions, is probably familiar with the dreaded 2 00:00:04,640 --> 00:00:08,080 DLL error when you're in the middle of trying to do something. 3 00:00:08,080 --> 00:00:12,200 Although DLL files seem to be important given how much Windows complains when one is broken 4 00:00:12,200 --> 00:00:16,960 or missing, it's not exactly obvious what they are, so let's explain why they're 5 00:00:16,960 --> 00:00:24,280 a big deal. DLL stands for Dynamic Link Library, but don't mistake them for a collection of Zelda NFTs. 6 00:00:24,280 --> 00:00:29,480 The reason they're called libraries is that DLLs contain shared code that multiple programs 7 00:00:29,480 --> 00:00:34,760 can link to and use, kind of like how real libraries contain shared books that many people 8 00:00:34,760 --> 00:00:39,360 can borrow. But DLLs have an important feature that books don't. 9 00:00:39,360 --> 00:00:44,800 Several programs can use one DLL at the same time, and once a DLL is loaded into a certain 10 00:00:44,800 --> 00:00:50,000 space in memory, any program that needs the code inside can request access to that memory 11 00:00:50,000 --> 00:00:54,520 space without the DLL having to be loaded over and over again. 12 00:00:54,520 --> 00:00:59,200 A good, simple example of this is this DLL file, which contains the code for bringing 13 00:00:59,200 --> 00:01:06,160 up a Windows pop-up dialog box. Since so many programs use this functionality, it makes sense for this code to be included 14 00:01:06,160 --> 00:01:10,920 in Windows as a DLL instead of writing it into every program from scratch. 15 00:01:10,920 --> 00:01:14,840 Another good example is the Device Driver, which is the code that allows Windows and 16 00:01:14,840 --> 00:01:18,120 other programs to communicate properly with hardware. 17 00:01:18,120 --> 00:01:23,360 Drivers often take the form of DLLs, though they can appear as .sys files in Windows Explorer, 18 00:01:23,360 --> 00:01:29,600 which allows multiple applications to access your GPU, keyboard, or printer, its drivers, 19 00:01:29,600 --> 00:01:34,800 at a time. And because DLLs are only loaded up when a program specifically asks for them instead 20 00:01:34,800 --> 00:01:39,480 of every time the program starts, they also prevent your RAM from filling up with tons 21 00:01:39,480 --> 00:01:45,720 of unnecessary code. This modularity means that new functionality such as game updates or support for different 22 00:01:45,720 --> 00:01:51,320 languages can be added to older programs simply by writing new DLLs rather than having to 23 00:01:51,320 --> 00:01:57,200 modify the program itself. That's not only more convenient, but you don't run the risk of inadvertently breaking the 24 00:01:57,200 --> 00:02:03,840 code of the main executable. But if DLLs are such a good idea, why are they so notorious for creating problems, often 25 00:02:03,840 --> 00:02:11,640 referred to as DLL hell? So one big reason DLLs cause problems is that when an application depends on lots of DLLs, 26 00:02:11,640 --> 00:02:15,420 it also means that application has many possible points of failure. 27 00:02:15,420 --> 00:02:20,600 If a DLL gets modified, there's no way for a program that loads up the DLL to ensure 28 00:02:20,600 --> 00:02:26,520 that the new code is compatible. And if it isn't, the program you want will often simply crash. 29 00:02:26,520 --> 00:02:31,260 You see, some programs will go messing around with DLLs in a way that they shouldn't. 30 00:02:31,260 --> 00:02:37,360 An installer, for example, may decide to modify a DLL in a way that helps that specific application, 31 00:02:37,360 --> 00:02:42,660 but can cause errors in the possibly many other programs that need the same DLL, but 32 00:02:42,660 --> 00:02:50,120 aren't compatible with the modified version. For a long time, Microsoft expected third-party software developers to verify that any DLLs 33 00:02:50,200 --> 00:02:54,360 they installed, especially if they overrode existing ones, would comply with accepted 34 00:02:54,360 --> 00:02:59,440 standards. But needless to say, with developers typically more concerned about making sure their own 35 00:02:59,440 --> 00:03:04,320 software works, it often simply didn't happen, and programs kept installing troublesome 36 00:03:04,320 --> 00:03:09,800 DLLs with impunity. Mercifully, this problem has been mitigated to a large extent in more recent versions 37 00:03:09,800 --> 00:03:15,760 of Windows. Microsoft has locked down system DLLs so that third-party applications can't mess with 38 00:03:15,760 --> 00:03:19,840 them unless they've actually been authorized by Microsoft itself. 39 00:03:19,840 --> 00:03:24,240 DLLs can now also track DLL installations to try to prevent unknown DLLs from making 40 00:03:24,240 --> 00:03:30,560 their way onto the system, as well as to allow two different versions of a DLL to exist simultaneously 41 00:03:30,560 --> 00:03:36,000 to prevent programs that rely on an older revision from breaking when you add a new one. 42 00:03:36,000 --> 00:03:41,120 And with modern PCs having a lot more memory than the computers of the 90s and early 2000s, 43 00:03:41,120 --> 00:03:45,880 the memory limitations that necessitated DLLs in the past aren't as prevalent today, meaning 44 00:03:45,880 --> 00:03:50,480 that modern programs often don't rely on DLLs nearly as much. 45 00:03:50,480 --> 00:03:54,960 Maybe stuffing 64 gigs of RAM in your personal rig wasn't such a big mistake after all. 46 00:03:54,960 --> 00:03:59,720 But you know what is a mistake? 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