Software entities are more complex for their size than perhaps any other human construct, because no two parts are alike (at least above the statement level). If they are, we make the two similar parts into one, a (1), open or closed.In this respect software systems differ profoundly from computers, buildings, or automobiles, where repeated elements abound.Digital computers are themselves more complex than most things people build; they have very large numbers of states.This makes conceiving, describing, and testing them hard.Software systems have orders of magnitude more(2)than computers do.Likewise, a scaling-up of a software entity is not merely a repetition of the same elements in larger size; it is necessarily an increase in the number of different elements.In most cases, the elements interact with each other in some(3)fashion, and the complexity of the whole increases much more than linearly.The complexity of software is a(an) (4)property, not an accidental one.Hence descriptions of a software entity that abstract away its complexity often abstract away its essence.Mathematics and the physical sciences made great strides for three centuries by constructing simplified models of complex phenomena, deriving, properties from the models, and verifying those properties experimentally. This worked because the complexities(5)in the models were not the essential properties of the phenomena. It does not work when the complexities are the essence. Many of the classical problems of developing software products derive from this essential complexity and its nonlinear increases with size. Not only technical problems but management problems as well come from the complexity.5、____
A.fixed
B.included
C.ignored
D.tabilized
软件实体规模上或许比其他任何人类创造的结构要更为复杂,因为没有两个部分是一样的(至少在语句级以上)。如果他们一样,我们便将这两个相似的部分合到一起,成为一个子程序,打开或关闭。在这一点上,软件系统与计算机、建筑或汽车经常混合使用一些重复的元件有很大区别。数字计算机本身比人类所建造的大多数事物都要复杂,他们有超级多的状态。这使得对他们进行想象、描述和测试都很困难。软件系统的状态数目更是比计算机的超出几个数量级。同理,软件实体的扩展不单是这一批元件变大一点,它必将是大量不同元件都有增加。在大多数情况下,构件以非线性的方式相互作用,而整体的复杂性远超线性增加。软件的复杂的特点具有必然性,并非偶然。因此,对于软件实体的描述,剥离了它的复杂性往往就等于剥离了它的本质。过去这三个世纪,通过对复杂的现象构建出简化模型,从模型的属性再倒推,并通过实验验证这些属性,数学和物理科学取得了长足的进步。这之所以行之有效,是因为模型中忽略掉的复杂特性并不是现象中重要的本质属性。而当这些复杂性很重要时,这种方法就会失效。
一台主机的IP地址为202.123.25.36,掩码为255.255.254.0。如果该主机需要在该网络进行直接广播,那么它应该使用的目的地址为( )
在计算机系统的日常维护工作中,应当注意硬盘工作时不能__(2)__。另外,需要防范病毒,而__(3)__是不会被病毒感觉的。
有 4 个 IP 地址:201.117.15.254、201.117.17.01、201.117.24.5 和 201.117.29.3,如果子网掩码为 255.255.248.0,则这 4 个地址分别属于3个子网;其中属于同一个子网的是()
在异步通信中,每个字符包含1位起始位、7位数据位、1位奇偶位和1位终止位,每秒钟传送200个字符,采用4相位调制,则码元速率为()。
在 Windows 中,运行( )命令得到下图所示结果。以下关于该结果的叙述中,错误的是( )。
Pinging 59.74.111.8 with 32 bytes of data:
Reply from 59.74.111.8: bytes=32 time=3ms TTL=60
Reply from 59.74.111.8: bytes=32 time=5ms TTL=60
Reply from 59.74.111.8: bytes=32 time=3ms TTL=60
Reply from 59.74.111.8: bytes=32 time=5ms TTL=60
Ping statistics for 59.74.111.8:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 3ms, Maximum = 5ms, Average = 4ms
在ISO OSF/RM参考模型中,七层协议中的__(1)__利用通信子网提供的服务实现两个用户进程之间端到端的通信。在这个模型中,如果A用户需要通过网络向B用户传送数据,则首先将数据送入应用层,在该层给它附加控制信息后送入表示层;在表示层对数据进行必要的变换并加头标后送入会话层;在会话层加头标送入传输层;在传输层将数据分解为__(本题)__后送至网络层;在网络层将数据封装成__(3)__后送至数据链路层;在数据链路层将数据加上头标和尾标封装成__(4)__后发送到物理层;在物理层数据以__(5)__形式发送到物理线路。B用户所在的系统接收到数据后,层层剥去控制信息,把原数据传送给B用户。
在OSI/RM中,解释应用数据语义的协议层是()。
在TCP/IP协议栈中,ARP协议的作用是(),RARP协议的作用是(请作答此空)。
在地址 http://www.dailynews.com.cn/channel/welcome.htm 中,www.dailynews.com.cn 表示( ),welcome.htm 表示(请作答此空)。
在电子表格软件Excel中,假设A1单元格的值为15,若在A2单元格输入“=AND(15<A1,A1<100)”,则A2单元格显示的值为 ()