Driver DLLs: Using Real Mode Services
Karen Hazzah · 1996
Driver DLLs: Using Real Mode Services Windows applications run in protected mode, but they can and do use real mode DOS and BIOS services. Whether a DOS application running under Windows calls the C library read function, or a Windows application calls the Windows 1 read function, the read eventually boils down to a simple call to DOS through INT 21 h, just as it does in a program running under DOS. In addition to using DOS and BIOS services, Windows applications may also use other real mode services such as TSRs or DOS device drivers.