A few more routines in the Dos and WinDos units besides the ones mentioned under Keep; GetIntVec; SetIntVec, like Intr or DosVersion, are meaningless on non-Dos systems. By default, the Dos unit does not provide these routines (it only provides those that are meaningful on all systems, which are most of its routines, including the most commonly used ones). If you need the unportable ones, you get them by using the System unit (see - -uses=System - Swap; HeapError; etc.) and defining the symbol __BP_UNPORTABLE_ROUTINES__ (by giving -D__BP_UNPORTABLE_ROUTINES__ on the command line). If you use Intr or MsDos, your program will only compile under DJGPP then. Other routines, e.g. DosVersion are emulated quite roughly on other systems. Please see the notes in the Dos unit (see Dos) for details.