单选题在传统关系系统中，对关系的错误描述是 (19) 。

单选题DDBS的分片模式和分配模式均是______。

单选题面向对象数据模型中不包含 ________ 。

单选题数据库是存储在一起的相关数据的集合，能为各种用户共享，且______。

单选题在面向数据流的设计方法中，一般把数据流图中的数据划分为 (8) 两种。 A．数据流和事务流 B．变换流和数据流 C．变换流和事务流 D．控制流和事务流

单选题在软件项目管理中可以使用各种图形工具来辅助决策，下面对Gantt图的描述中，不正确的是 (22) 。

单选题下列要素中，不属于DFD的是 7 。当使用DFD对一个工资系统进行建模时， 8 可以被认定为外部实体。

单选题Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an (16) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (17) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim's address book, previous emails, web pages (18) . As administrators seek to block dangerous email attachments through the recognition of well-known (19) , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users. Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which, while displaying some cute animation, simultaneously runs commands in the background to steal your passwords and give the (20) access to your network.

单选题有关概念结构设计，下列说法正确的是 (15) 。

单选题With the widespread use of the personal computer, many authorities in the field of 11 have pointed out the need for computer literacy. Unfortunately, there is no 12 agreement as to what the term "computer literacy" means. Some feel that computer literacy means knowing how to make the computer "compute"; that is knowing how to program computers in one or more programming languages. Others feel that knowing how to program is merely a small segment of computer literacy. These people 13 the major emphasis in schools should be on teaching how to effectively use the many software packages that are available. Still others suggest that computer literacy education is not required. They suggest that computers are being so rapidly integrated into our society that using a computer will be as 14 as using a telephone or a video tape recorder, and that special education will not be necessary. 15 of one"s definition of computer literacy, it is recognized by most that learning to use a computer is indeed an important skill in modern society.

单选题现采用4级流水线结构分别完成一条指令的取指、指令译码和取数、运算以及送回运算结果4个基本操作，每步操作时间依次为60ns、100ns、50ns和70ns。该流水线的操作周期应为 9 ns。若有一小段程序需要用20条基本指令完成(这些指令完全适合于流水线上执行)，则得到的第一条指令结果需 10 ns，完成该段程序需 11 ns。 在流水线结构的计算机中，频繁执行 12 指令时会严重影响机器的效率。当有中断请求发生时，采用不精确断点法，则将 13 。

单选题不能激活触发器执行的操作是 (4) 。

单选题数据库系统三级结构的关系，可以概括为 ____ 。

单选题内存按字节编址，地址从A4000H到CBFFFH，共有 (1) 。若用存储容量为 32K×8b的存储器芯片构成该内存，至少需要 (2) 片。

单选题在高速并行结构中，速度最慢但通用性最好的是______。 A．相联处理机 B．数据流处理机 C．多处理机系统 D．专用多功能单元

单选题数据字典和PAD(问题分析图)是两类非常重要的软件工具，它们主要分别用在软件生存周期中 12 阶段和 13 阶段。

单选题 2．一棵查找二叉树，其结点A、B、C、D、E、F依次存放在一个起始地址为n(假定地址以字节为单位顺序编号)的连续区域中，每个结点占4个字节：前二个字节存放结点值，后二个字节依次放左指针、右指针。若该查找二叉树的根结点为E，则它的一种可能的前序遍历为{{U}} (1) {{/U}}，相应的层次遍历为{{U}} (2) {{/U}}。在以上两种遍历情况下，结点 C的左指针Lc的存放地址为{{U}} (3) {{/U}}，Lc的内容为{{U}} (4) {{/U}}。结点A的右指针Ra的内容为{{U}} (5) {{/U}}。

单选题关于OLAP和OLTP的说法，下列不正确的是______。

单选题并行数据库体系结构中具有独立处理机、内存和磁盘的是 (10) 结构。

单选题在关系代数的专门关系运算中，从表中选出满足某种条件的元组的操作称为 ______。 A．选择 B．投影 C．连接 D．扫描