单选题 (56) 中的属性不依赖于其它非主属性。
单选题 Typically, these are concern with the establishment of
______ the network and with the control of the flow of messages across this
channel. The provision of such facilities is only part of the network
requirements, however, since in many applications the communicating computers
may be of different types. This means that they may use different programming
languages and, more importantly, different forms of ______ interface between
user (application) prograrma, normally referred to, as application processes or
APs, and the underlying communication services may be ______ For example, one
computer may be a small single-user computer, while another may be alarge ______
system. In the earlier days of computer communication, these issues meant that
only closed communities of computers (that is, from the same manufacturer) could
communicate with each other in a meaningful way. IBM's Systems Network
Architecture (SNA) and DEC's Digital Network Architecture (DNA) are just
two examples of communication software packages produced by manufacturers to
allow their systems to be int ercormected together. These proprietary packages,
however, of which there am still many inexistence, do not address the problem of
universal interconnect ability, or open systems interconnection. In an attempt
to alleviate this problem, ______, in the late 1970s, formulated a reference
model to provide a common basis (or the coordination of standards developments
and to allow existing and evolving standards acivities to be placed into
perspective with one another.
单选题给定关系模式R(U，F)，U=A,B,C,D,E，F=B→A，D→A，A→E，AC→B，其候选关键字为 (40) ，则分解ρ=R1(ABCE)，R2(CD)满足 (41) 。
单选题要判断宇长为16位的整数a的低四位是否全为0，则干( )。
单选题王某是某公司的软件设计师，完成某项软件开发后按公司规定进行软件归档，以下关于该软件的著作权的叙述中，正确的是
单选题IP地址通常是一个32位的数，用于标识网络上系统的位置每个IP地址内部都分成两部分：网络ID和主机ID网络ID和主机ID分别占了 (43) 192.168.0.1属于 (44) 地址。
单选题计算机感染特洛伊木马后的典型现象是 (9) 。 A．程序异常退出 B．有未知程序试图建立网络连接 C．邮箱被垃圾邮件填满 D．Windows系统黑屏
单选题
单选题采用UML进行软件设计时，可用 (16) 关系表示两类事物之间存在的特殊/一般关系，用聚集关系表示事物之间存在的整体/部分关系。 A．依赖 B．聚集 C．泛化 D．实现
单选题关系模式R 属性集为{A，B，C}，函数依赖集F={AB→C, AC→B, B→C}，则R 属于 （42） 。
单选题电子邮件应用程序利用POP3协议 (68) 。
单选题以下关于面向对象数据库系统的叙述中，错误的是______。
单选题数据模型的三要素中不包括（ ）
单选题为了建立目录与文件之间的链接，顺利实现共享，可以引用索引结点。将文件的物理地址及其它的文件属性等信息， (22) ，在文件目录中设置文件名及指向索引结点的指针。
单选题进程PA不断地向管道写数据，进程PB从管道中读数据并加工处理，如下图所示。如果采用PV操作来实现进程PA和进程PB间的管道通信，并且保证这两个进程并发执行的正确性，则至少需要（26）。
单选题对象关系数据库中，员工(工号，姓名，性别，联系电话)表中的联系电话为多值属性，则员工属于 (62) ，在SQL99标准中可以使用 (63) 来实现。
单选题若某时期投入市场的某型号机器上编制的软件能不加修改地运行于在它之前投入市场的机器上称做 (34) 。 A) 向上兼容 B) 向下兼容 C) 向前兼容 D) 向后兼容