Primary memory is stored on chips located(66). In addition, computers usually use disks as second memory, for example,(67)disks located inside the computer.

(71)

Primary memory is stored on chips located(66). In addition, computers usually use disks as second memory, for example,(67)disks located inside the computer.

Certain keywords or phrases in a hypertext document are linked to other online documents through(75).

(67)

The color display will use both chrominance and luminance information. A black and white display uses(74).

(66)

(65)

(64)

(62)

SQL的DDL主要是定义(20)。若有：

 学生关系模式S(Sno，Sname，Age，Sex)，

 课程关系模式C(Cno，Cname，Teacher)以及

 成绩关系模式SC(Sno，Cno，Grade)，其中S的属性分别表示学生的学号、姓名、年龄、性别，C的属性分别表示课程号、课程名、任课教师姓名，SC的属性分别表示学号、课程号、成绩。

 若要在表S中增加一个“家庭住址”(Address)属性，应使用语句(21)Address VARCHAR(30)；若要在表S中删除Age属性，应使用语句：(22)；已知某课程的课程号为‘C1’，若要输出该课程的平均成绩，应使用语句：SELECT(23)WHERE Cno=‘C1’；若要删除表S、C和 SC，应使用(24)语句。