When a register used in the generated code of the compiler is accessed via a pointer, invalid operation may occur.

This is because the compiler generates codes on the assumption that a register in use will not be accessed via a pointer.

When the following registers are accessed via a pointer, program operation cannot be guaranteed.

*(int __near *)0xfef8 = 7;      //Since 0xffef8 is the address of register AX in bank 

                                //0, operation of a program including this 

                                //description and also using bank 0 is not guaranteed