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─────C/C++ Language─────────────────────────────────────────────────────────
 
     On entry to an interrupt handler, the DS register is initialized
     to the near data segment, allowing your interrupt handler to
     access global variables.
 
     In addition, all registers (except SS) are saved on the stack. You
     can access these registers within the function if you declare a
     function parameter list containing a formal parameter for each
     saved register. For example:
 
        void __interrupt __far int_handler( unsigned _es, unsigned _ds,
                                            unsigned _di, unsigned _si,
                                            unsigned _bp, unsigned _sp,
                                            unsigned _bx, unsigned _dx,
                                            unsigned _cx, unsigned _ax,
                                            unsigned _ip, unsigned _cs,
                                            unsigned flags )
        {
        ∙ ∙ ∙
        }
 
     You can omit parameters from the end of the list in your
     declaration, but you cannot omit parameters from the beginning of
     the list. For example, if your handler needs to use only DI and
     SI, you must still provide the ES and DS arguments, but not
     necessarily BX, DX, or those that follow.
 
     The compiler always saves and restores registers in the same
     fixed order. Thus, no matter what names you use in the formal
     parameter list, the first parameter in the list refers to ES, the
     second refers to DS, and so on.
 
     Do not give your parameters actual register names because they
     can conflict with the inline assembler. To prevent conflict and
     retain the documentation of the register names, use an underscore
     when naming your parameters (for example, _ax, _bx).
 
     Passing Additional Arguments
 
     You can pass additional arguments if your interrupt handler is to
     be called directly from C or C++ rather than by an INT instruction.
     To do this, you must declare all register parameters and then
     declare your parameter at the end of the list.
 
     Changing Parameters
 
     If you change any parameters of an interrupt handler during
     function execution, the corresponding register contains the
     changed value when the function returns. The code below causes DI
     to contain -1 when int_handler returns.
 
        void __interrupt __far int_handler( unsigned _es, unsigned _ds,
                                            unsigned _di, unsigned _si)
        {
            _di = -1;
        }
 
     Do not modify the values of IP or CS in an interrupt handler. If
     you need to modify a flag, use the bitwise-OR operator (|) so
     that the other flags are not changed.
                                    -♦-