从表面上看，保护模式和实模式并没有太大的区别，二者都使用了内存段、中断和设备驱动来处理硬件，但二者有很多不同之处。我们知道，在实模式中内存被划分成段，每个段的大小为64KB，而这样的段地址可以用16位来表示。内存段的处理是通过和段寄存器相关联的内部机制来处理的，这些段寄存器（CS、DS、 SS和ES）的内容形成了物理地址的一部分。具体来说，最终的物理地址是由16位的段地址和16位的段内偏移地址组成的。用公式表示为：物理地址=左移4位的段地址+偏移地址。-On the surface, protected mode and real mode is not much difference between the two are the use of the memory, Drivers interruption and equipment to deal with the hardware, but there are many differences. We know that in real mode which has been divided into memory, each the size of 64 KB. and the addresses of 16 can be used to express. Memory of the handling of the adoption and register linked to the internal mechanisms to deal with, of these registers (CS, DS, SS and ES) with the formation of a part of the physical address. Specifically, the ultimate physical address is 16 of the 16 addresses and the addresses of migration within the composition. The use of the formula is expressed as : physical address = 4 bits of the address offset address.