DOS Compatibility Box
Facility provided by OS/2 Version 1.3 that allows a single real mode (DOS) application to execute under control of OS/2, occupying the lowest 640 KB of physical memory. A real mode application executing in this way may coexist with other protected mode applications in the same system. Certain restrictions are imposed on applications executing in the DOS Compatibility Box; an application may not be a TSR application, nor should it be a time-dependent application (such as a terminal emulator). These limitations are overcome by the Multiple Virtual DOS Machines feature implemented by OS/2 Version 2.0.