Many networks on the market today are based on the Microsoft Networks standard, also known as MS-NET. These networks support a set of standard MS-DOS functions that perform network activities, such as redirecting drive letters.
Current versions of Windows automatically handle these MS-DOS functions. However, in order to maintain compatibility with future Windows products, your application should not make MS-DOS calls by using Interrupt 21h. Instead, it should set up all the registers for Interrupt 21h and then make a far call to the Windows DOS3Call function.
For a full description of the DOS3Call function, see the Microsoft Windows
Programmer's Reference, Volume 2. For more information about Microsoft
Networks functions, see The MS-DOS Encyclopedia.