For virtually any kind of program execution to take place, at least the code-segment (CS), data-segment (DS), and stack-segment (SS) registers must be loaded with valid segment selectors.

• 每个段寄存器都提供一种专门的寻址用途。如代码段(cs)、数据段寄存器(DS)、堆栈段寄存器(SS)。