DOS supports multiple, concurrent DOS applications, where each runs as a single-threaded, protect-mode OS/2 application. This support provides:
Multiple DOS sessions also can run along with other OS/2 sessions. Each DOS session has more memory than the DOS box implemented in previous OS/2 versions; more than 620KB of conventional memory (DOS=HIGH,UMB statement in CONFIG.SYS) is available for each DOS session. OS/2 2.0 also supports the use of LIM EMS and XMS. This provides additional memory for those DOS applications that can use such extensions. OS/2 2.0 maps this extended or expanded memory into the system's normal, linear memory address space and manages it the same as any other allocated memory.
The ability of a DOS session to run within a window on the OS/2 desktop provides immediate productivity gains to existing DOS applications, because they can use OS/2 desktop features. These features include window manipulation and the ability to cut, copy, and paste information between applications using the clipboard.
Application compatibility in the DOS session also is improved over previous OS/2 versions. The DOS session can be used to run DOS-based communications applications and other applications that address hardware I/O devices through the use of VDDs. These VDDs map the device driver calls from the applications to the appropriate physical device driver within the operating system. For more information, see "Virtual Device Drivers."
Application compatibility in a DOS session is further enhanced by the DOS Settings feature, which allows DOS sessions to be customized to suit the requirements of the applications running in them. Properties such as video characteristics, hardware environment emulation, and the use of memory extenders all can be customized using this feature. For more information, see "DOS and WIN-OS/2 Settings."