单选题设置日志文件的目的不包括
单选题有关二叉树的下列说法正确的是 (44) 。
单选题As mentioned above, C imposes relatively few built - in ways of doing things on the program- mer. Some common tasks, such as manipulating (66) , (67) , and doing (68) (I/O), are performed by calling on library functions. Other tasks which you might want to do, such as creating or listing directories, or interacting with a mouse, or displaying windows or other (69) elements, or doing color graphics, are not defined by the C language at all. You can do these things from a C program, of course, but you will be calling on services which are peculiar to your programming environment (70) , processor, and operating system) and which are not defined by the C standard. Since this course is about portable C programming, it will also be steering clear of facilities not provided in all C environments.
单选题关系规范化是在数据库设计的（ ）阶段进行。
单选题读下面的流程图，其最后结果是 (3) 。
单选题对分组查询结果讲行筛选的是（ ），其条件表达式中可以使用聚集函数
单选题“防火墙”是在互联网与内部网之间建立一个安全网关，以防止非法用户的侵入，它通常由屏蔽器和代理服务器组成，其中，屏蔽路由器是一个 (47) ，但是它却难以防止黑客的攻击，其主要原因在于： (48) 。
单选题某高校的管理系统中有学生关系为：学生(学号，姓名，性别，出生日期，班级)，该关系的数据是在高考招生时从各省的考生信息库中导入的，来自同一省份的学生记录在物理上相邻存放，为适应高校对学生信息的大量事务处理是以班级为单位的应用需求，应采取的优化方案是______。 A．将学号设为主码 B．对学号建立UNIOUE索引 C．对班级建立CLUSTER索引 D．对班级建立UNIOUE索引
单选题下述协议中与安全电子邮箱服务无关的是（ ）
单选题交换机是根据目的地址进行帧转发的，其主要作用是 (41) ，使网络总吞吐量远大于单个端口的速率。
单选题 The traditional model for systems development was that an
IT department used ______ which is a process-centered technique, and consulted
users only when their input or approval was needed. Compared with traditional
methods, many companies find that JAD allows ______ to participate effectively
in the requirements modeling process. When properly used, JAD can result in a
more accurate statement of system requirements, a beret understanding of common
goals, and a stronger commitment to the success of the new system. RAD is a
______ technique that speeds up information systems development and produces a
functioning information system. While the end product of JAD is a(an) ______，the
end product of RAD is the new information system. The RAD model consists of four
phases. During the ______, users interact with systems analysts and develop
models and prototypes that represent all system processes, outputs, and
inputs.
单选题如果“2X”的补码是“90H”，那么X的真值是（ ）。
单选题一条指令的执行可划分成取值，分析和执行三个部分，不同的部分由不同自由独立的硬件完成设每一指令完成取值，分析和执行三部分的时间分别为2ns，3ns，1ns现有100条指令，若顺序执行这些指令需要 (23) ；若采用流水方式执行这些指令则需要 (24) 。
单选题一个触发器有三个基本部件 (62) 。
单选题某有向强连通图有n个顶点，则其边数不小于 (26) 。
单选题在面向对象数据库系统的数据类型中，对象属于______类型。
单选题DMA控制方式是在（ ）之间直接建立数据通路进行数据的交换处理
单选题以下各文件格式中， (45) 不是声音文件的格式。
单选题一般来说，软件开发环境都具有层次式的结构， (54) 不是其中的一个层次结构。