up to 3 characters for the extension. Otherwise, filenames will be altered to fit the pattern. There are versions available on the DOSBox website that support long filenames, at the cost of possible incompatibility with some older programs. The focus of the vanilla version is on gaming, and features such as support for Ctrl-Break may be missing. Some of the alternative versions support features not present in the vanilla version such as APM power off, direct parallel port passthrough for printing, and support for East Asian characters. Because DOSBox accesses the host computer's file system, there thus is a risk of DOS malware exploiting the emulator's security vulnerabilities and causing damage to the host machine, although these vulnerabilities continue to be patched with new DOSBox updates. Users can also capture screenshots and record videos of DOS sessions, although a codec is required to play the videos. It is also possible to record OPL sound card and MIDI commands, as well as save sound output on a WAV file. Keyboard keys and the buttons of a game controller can be mapped to other keys and combinations thereof. OS emulation DOSBox is a full-system emulator that provides BIOS interrupts and contains its own internal DOS-like shell. This means that it can be used without owning a license to any real DOS operating system. Most commands that are found in COMMAND.COM are supported, but many of the more advanced commands found in the latest MS-DOS versions are not. In addition to its internal shell, it also supports running image files of games and software originally intended to start without any operating system. Besides emulating DOS, users can also run Windows 3.0 and applications designed for it, as well as versions of Windows within the Windows 9x family. When the DOSBox application is opened, it automatically mounts to a virtual, permanent Z: drive that stores DOSBox commands and utilities. The reasons for the virtual drive are related to security, but the user can mount a different drive letter in the emulator to a directory, image file, floppy disk drive, or CD-ROM drive on the host to access its data. A configuration file and its AUTOEXEC section can be used to respectively configure DOSBox settings and execute DOS commands at startup. Hardware emulation DOSBox is capable of running DOS programs that require the CPU to be in real mode or protected mode. Since DOSBox can