The Microsoft Mouse driver makes its functions available to application programs via Int 33H. These functions have become a de facto standard for pointer device drivers of all varieties. Unlike the other function calls described in this section, the Microsoft Mouse driver is not part of the ROM BIOS but is loaded by a DEVICE= directive in the CONFIG.SYS file. All mouse-function information applies to the Microsoft Mouse driver version
1.Earlier versions of the driver may not support all of these functions.