There are some applications that must run on a specific version of DOS because they require characteristics unique to that version. Therefore, OS/2 2.0 enables users to boot (start) specific versions of DOS, such as 3.3, 4.0, and 5.0, or DRDOS 6.0, in a DOS session. This capability helps ensure compatibility with version-specific DOS applications and device drivers. That includes block device drivers, such as local area network (LAN) requesters, that are needed for network support.