 Examples can be found in MS-DOS/PC DOS; when running on 286 or higher processors, the resident executable loader contains code specially designed to detect and fix certain widespread applications and stub loaders (such as programs linked with older versions of Microsoft's EXEPACK or Rational Systems' 386 DOS extenders) by patching the loaded program image before executing it, or where DOS patches Windows (WINA20.386) Over the course of development, DR-DOS also had to be modified to not only emulate many undocumented peculiarities of MS-DOS and PC DOS, but also actual bugs in the kernel and several drivers, in order to make certain other drivers and applications run on DR-DOS, when they were tested on specific versions of MS-DOS only.Windows, which has traditionally emulated many old system bugs to allow older low-level programs to run, is another example.As a result, Wine, which makes it possible to run many Windows applications on other platforms, also needs to maintain bug compatibility with Windows.