前面提到，数据可存储在寄存器、内存单元，I/O端口。现在需考虑的问题是：在编程时如何访问这些数据？



（1）若在寄存器中，可直接用寄存器名来访问寄存器中的数据。

（2）若在内存单元或I/O端口，则需按地址访问。-As mentioned earlier, the data may be stored in a register, a memory unit, I/O port. Issues to be considered now is: how to access the data in the programming? (1) register name in the register, and can be directly used to access the data in the register. (2) If the memory unit or I/O port, you need to be accessed by address.