VHDL设计8位算术逻辑单元（alu），实现清零、逻辑乘、逻辑加、逻辑异或、算术加、逻辑左移一位、逻辑右移一位等功能-VHDL design eight the arithmetic/logic unit (alu), realize the reset, logic, logic and, by different or, arithmetic and logic, logical moves left a, logic move to the right a etc.