What are the functions under dos h in c plus plus language?

Answer 1

Quote from the Microsoft Visual Studio 2010 version of dos.h:

"Defines the structs and unions used for the direct DOS interface routines; includes macros to access the segment and offset values of far pointers, so that they may be used by the routines; and provides function prototypes for direct DOS interface functions."

However, this description bears little resemblance to the file content. The structure, _diskfree_t, is declared and the standard definitions for file attributes (normal, readonly, hidden, etc) are also defined. But that's all. No macros, no unions, no function prototypes whatsoever.

The actual definitions are contained in crtdefs.h (the common runtime definitions), which is included in dos.h.