计算机指令系统中采用不同寻址方式的主要目的是(3)。在下列寻址方式中，取操作数速度最慢的是(4)。

() is a mechanism used for protecting the users outside of network from accessing some non-authorized computer resources.

(80)

For many years, the principle goal of computer(73) was to write short pieces of code that would execute quickly. The (74) needed to be small, because memory was expensive, and it needed to be fast ,because processing power was also expensive.

(78)

A(71) is a data type whose major attributes are determined by the rules governing the insertion and deletion of its elements. The only element that can be deleted or removed is the one that was inserted most(72). Such a structure is said to have a last-in/first-out (LIFO) behavior, or protocol.

(76)

(75)

在寄存器间接寻址中，若指令指定的寄存器是BX、SI、或者DI，则默认操作数存放在(46)段中。这时要用寄存器(47)的内容作为段地址。对于指令MOV BX，[SI]，假设数据段寄存器DS=1000H，代码段寄存器CS=4000H，堆栈段寄存器SS=7000H，SI=2000H，则操作数的物理地址为(48)。

(73)

中断是CPU与外部设备进行数据交换的重要方式。CPU响应中断时必须具备三个条件，分别为：外部提出中断请求、本中断未屏蔽、(4)。CPU响应中断后，必须由(5)提供地址信息，引导程序进入中断服务子程序；中断服务程序的入口地址存放在(6)中。