关系R和s具有相同的关系模式，由属于R同时属于S的元组构成集合，这种运算是______。

The Internet is based oil the concept of a(n)______relationship between computers．

Information-based occupations now take the______share of employment in many industrial societies such as the United States and the United Kingdom．

The earliest method of delivering telecommunications is the ______．

When you install a new device in a computer,you have to add the correct device______to the operating system to allow the computer to communicate with the device．

In the system development process,modularity is a very well-established principle used in the______phase．

(78)

(77)

栈和队列是两种特殊的线性表(linear list)。栈的特点是(63)。队列的特点是(64)。二者的共同特点是只能在它们的(65)处添加和删除结点。

(76)

(74)

(75)