2019年计算机等级考试四级笔试练习题

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2019年全国计算机等级考试四级笔试试题及答案2

2019年全国计算机等级考试四级笔试试题及答案2(16) 下列关于时间片轮转法的叙述中，哪个是错误的？____。

A）在时间片轮转法中，系统将CPU的处理时间划分成若干个时间段B）就绪队列的诸进程轮流上CPU运行，每次最多运行一个时间片C）当时间片结束时，运行进程自动让出CPU，该进程进入等待队列D）如果时间片长度很小，则调度程序剥夺CPU的次数频繁，加重系统开销(17) 并行技术可使系统各种硬件资源尽量并行工作，这样的程序执行环境具有独立性、随机性和____。

A）封闭性 B）多发性 C）顺序性 D）资源共享性(18) 根据对进程的统计，在一段时间内其程序的执行往往表现出高度的局部性，这中局部性可能包括____。

Ⅰ.时间局部性Ⅱ.缓冲区局部性Ⅲ. 空间局部性而准确地叙述了程序局部性的是A) Ⅰ和Ⅱ B) Ⅱ 和Ⅲ C) Ⅲ D) Ⅰ和Ⅲ(19) 下列关于工作集的叙述中，哪个是错误的____。

？Ａ)工作集大小与窗口尺寸密切相关B) 统计工作集大小的工作由软件完成C) 统计工作集大小的工作有较大的系统开销D) 分配给进程的物理页面数应与该进程当前工作集大小一致(20) 在文件系统中，文件的逻辑结构可分为两类，他们是____。

A）流式文件和记录式文件 B）字符文件和二进制文件C）程序文件和数据文件 D）内存文件和外存文件(21) 下列关于CPU对外部设备的直接内存存取（DMA）控制方式叙述中，哪个是错误的？____。

A) DMA方式用于高速外部设备与内存之间批量数据的传输B) 当本次DMA传送数据的开始时，产生中断，请求CPU实行处理C) DMA方式无须CPU干预D) DMA采取窃取总线控制权的方法占用总线(22) 一个进程能够包括多个线程，各线程____。

A) 共享分配给进程的主存地址空间 B) 必须串行工作C) 是资源分配的独立单位 D) 共享进程的PCB(23) UNIX系统中提供了一种进程间的信息传送机制，把一个进程的标准输出与另一个进程的标准输入连接起来，这种机制称为____。

2019年4月2019年9月全国计算机等级考试四级网络工程师试题及答案-38页精选文档

2019年4月全国计算机等级考试四级网络工程师笔试试卷一、选择题（每小题1分，共40分）。

（1）、设计一个宽带城域网将涉及“三个平台一个出口”，即网络平台、业务平台、管理平台和 cA、广域网出口B、局域网出口C、城市宽带出口D、卫星通道出口（2）、下列关于宽带城域网核心交换层特点的描述中，错误的是 dA、将多个汇聚层连接起来B、为整个城域网提供一个高速、安全与具有QoS保障能力的数据传输环境C、提供宽带城域网的用户访问Internet所需要的路由服务D、根据接入层的用户流量进行本地路由、过滤、流量均衡（3）、ADSL上行速率在 a A、64Kbps~640 Kbps B、640Kbps~7Mbps C、7Mbps~10Mbps D、10Mbps~20Mbps （4）、下列关于IEEE802.16标准的描述中，错误的是 b A、提供宽带城域网用户访问Internet所需要的路由服务 B、最高传输速率为234Mbps 32-134Mbps C、使用无线频段为10~66GHz D、与IEEE802.16标准工作组对应的论坛组织是WiMAX（5）、在网络需求详细分析中除包括网络总体需求分析、综合布线需求分析、网络可用性与可靠性分析、网络安全性需求分析，还需要做的工作是 a A、网络工程造价估算 B、网络工程进度安排 C、网络硬件设备选型D、网络带宽接入需求分析（6）、网络系统分层设计中层次之间的上联带宽与下一级带宽之比一般控制在 c A、1:1 B、1:10 C、1:20 D、1:40（7）、一台交换机具有24个10/100Mbps全双工端口和2个1000Mbps全双工端口，如果所有端口都工作在全双工状态，那么该交换机总带宽应为 d A、4.4Gbps B、6.4 Gbps C、6.8 Gbps D、8.8 Gbps（8）、某个IP地址的子网掩码为255.255.255.192，该掩码又可以写为 c A、/22 B、/24 C、/26 D、/28（9）、将内部专用IP地址转换为外部公用IP地址的技术是 b A、RAPR B、NAT C、DHCP D、ARP （10）、若某大学分配给计算机系的IP地址块为202.113.16.128/26，分配给自动化系的IP地址块为202.113.16.192/26，那么这两个地址块经过聚合后的地址为 c A、202.113.16.0/24 B、202.113.16.0/25 C、202.113.16.128/25 D、202.113.16.128/24（11）、下列对IPv6地址FE80:0:0:0801:FE:0:0:04A1的简化表示中，错误的是 aA、FE8::801:FE:0:0:04A1B、FE80::801:FE:0:0:04A1C、FE80:0:0:801:FE::04A1D、FE80:0:0:801:FE::4A1（12）、下列关于路由信息协议RIP的描述中，错误的是 bA、路由刷新报文主要内容是由若干(V、D)组成的表B、矢量V标识该路由器可以到达的目的网络或目的主机的跳数C、路由器在接收到（V、D）报文后按照最短路径原则更新路由表D、要求路由器周期性地向外发送路由刷新报文（13）、下列关于OSPF协议的描述中，错误的是 dA、OSPF使用分布式链路状态协议B、链路状态协议“度量”主要是指费用、距离、延时、带宽等C、当链路状态发生变化时用洪泛法向所有路由器发送信息D、链路状态数据库中保存一个完整的路由表（14）、在不同AS之间使用的路由协议是 c A、RIP B、OSPF C、BGP-4 D、ISIS （15）下列关于综合布线的描述中，错误的是 bA、终端有高速率要求时，水平子系统可采用光纤直接铺设到桌面B、多介质信息插座是用于连接双绞线C、干线线缆铺设经常采用点对点结合和分支结合两种方式D、采用在管理子系统中更改、增加、交换、扩展线缆的方式来改变线缆路由（16）网桥转发数据的依据是 b A、ARP表 B、MAC地址表 C、路由表 D、访问控制列表（17）一台Cisco交换机和一台3COM交换机相连，相连端口都工作在VLAN trunk模式，这两个端口应使用的VLAN协议是 dA、ISL 和IEEE802.10B、ISL 和ISLC、ISL和 IEEE802.1QD、IEEE802.1Q和IEEE802.1Q（18）有3台交换机分别安装在办公楼的1~3层，同属于财务部门的6台PC机分别连接在这3台交换机的端口上，为了提高网络安全性和易管理性，最好的解决方案是 d A、改变物理连接，将6台PC机全部移动到同一层B、使用路由器，并用访问控制列表（ACL）控制主机之间的数据流C、产生一个VPN，并使用VTP通过交换机的Trunk传播给6台PC机D、在每台交换机上建立一个相同的VLAN,将连接6台PC机的交换机端口都分配到这个VLAN中（19）当交换机到根网桥的间接链路出现失效故障时（如图，链路L1失效），STP协议会将交换机C的阻塞端口的工作状态转换为转发状态，为了省去端口状态转换等待时间，让端口直接由侦听和学习状态转换为转发状态，需配置交换机 STP的可选功能是 cA、PortFastB、UplinkFastC、BackboneFastD、BPDU Filter（20）下列删除VLAN的命令中，无法执行的是 a A、no vlan 1 B、no vlan 2 C、no vlan 500 D、no vlan 1000（21）当路由表中包含多种路由信息源时，根据缺省的管理距离值，路由器在转发数据包时，会选择的路由信息源是dA、RIPB、IGRPC、OSPFD、Static（22）只封禁一台地址为193.62.40.230主机的access-list的正确配置是 bA、access-list 110 permit ip any anyB、access-list 110 deny ip host 193.62.40.230 anyaccess-list 110 deny ip host 193.62.40.230 any access-list 110 deny ip any host 193.62.40.230access-list 110 deny ip any host 193.62.40.230 access-list 110 permit ip any anyC、access-list 110 deny ip host 193.62.40.230 anyD、access-list 110 deny ip host 193.62.40.230 anyaccess-list 110 deny ip any host 193.62.40.230 access-list 110 permit ip any anyaccess-list 110 deny ip any host 193.62.40.230（23）在某园区网中，路由器R1的GE0/1(212.112.8.5/30)与路由器R2的GE0/1(212.112.8.6/30相连，R2的GE0/2(212.112.8.9/30)与R3的GE0/1(212.112.8.10/30)相连，R3的GE0/2(212.112.8.13/30)直接与Internet 上的路由器相连，路由器R1缺省路由的正确配置是 a A、ip route 0.0.0.0 0.0.0.0 212.112.8.6B、ip route 0.0.0.0 0.0.0.0 212.112.8.9C、ip route 0.0.0.0 0.0.0.0 212.112.8.10D、ip route 0.0.0.0 0.0.0.0 212.112.8.13（24）某局域网用一台路由器互连4个子网。

2019年12月四级真题及解析【已审校】【全国青少年软件编程等级考试】

代码块可以讲两组文本内容连接到一起。

A+B排除A,B。

C选项中的选择范围是0-6项，D选项中的选择范围是1-6项。

列表中的项目是从第一项开始。

本题答案是：D7.当程序重复执行5次之后a的值大于10了，所以此时b的值为5。

本题答案是：B8.题目中高档礼品，选择标准是：脐橙果径大于6cm，重量大于150g。

所以是需要果径和重量同时满足要求。

所以需要用“与”代码块。

本题答案是：B9.根据题意可知，一共有三种情况，等于、大于、或者小于，所以需要多重判断，，本题需要两层可以使用两个如果那么否则来实现判断，如果回答等于电脑选择数则回答正确，否则就继续判断是大了还是小了，所以本题，答案选=是：C10.本题自定义代码块的功能是说出最大值。

程序运行后，自定义积木中的1表示5,2表示32,3表示8，经过比较得知本题答案是：C 11.点击角色需要同时满足按下鼠标和碰到鼠标两个条件，所以需要使用“与”代码块。

这两个条件需要一直检测，所以同时外层在外面需要加上嵌套重复执行代码块。

本题答案是:A12.本题转化代码语言：1+2*6=13。

本题答案是：B13.本题自定义代码块的功能为画N边形为画N，每边形画一条边旋转的角度相同，所以是正N边形。

本题答案是:C14.本题中a的第4个字符是c，每一个空格也也算一个字符，所以第8个字符是n。

本题答案是：B15.如果输入数正好能被2整除则输入数是偶数，否则，输入数为奇数。

C满足条件。

本题答案是:C判断题：16.每按下一次空格键，就会将下面的代码块执行一遍，每次列表的项数也会增加5开始没有删除列表的全部项目数，所以无法判断列表项目数。

本题答案：错误17.如果number能被2整除，则这个数应该是偶数，题中代码表述错误，所以不能判定奇偶数。

本题答案：错误18.变量a初始为1，循环10次后，增加到11。

表述正确在循环代码块内“和”随着“a”一直不断增加。

代码表达的数字逻辑是1+2+3+....+10，所以结果不为11.本题答案：错误19.S mart的第三个字符为a 但是后面的是1-9的随机数。

2019年全国计算机等级考试四级笔试试题2

2019年全国计算机等级考试四级笔试试题2一、选择题：((1)-(90))题,分为1分题和2分题,满分120分.除标注2分题外,其它均为1分题.)下列各题A)、B)、C)、D)四个选项中,只有一个是准确的,请将准确选项涂写在答题卡相对应位置上,答在试卷上不得分.(1) 一般情况下,操作数左移2位的结果是原操作数____。

A)整除2 B)乘以2 C)整除4 D)乘以4(2) 已知寄存器A存有带符号整数,且只作逻辑移位,HA和LA分别代表其位和最低位;寄存器B存有带符号整数,且只作算术移位,HB和LB分别代表其位和最低位. 当寄存器A与B都有右移位发生时,下述哪一个命题是准确的? ____。

(2分)A)HA与HB均成为0 B)HA与HB均成为1C)HA变成0但HB保持原值 D)HA保持原值但HB的值改变(3)若与非门的输入变量为A与B,输出变量为Y,则A和B分别为下述哪种情况时,Y才为0?____。

A)0,0 B)0,1 C)1,0 D)1,1(4)设S={1,2,3,4},下面哪个运算是S上的运算?_____。

A)X*Y=X-Y B)X*Y=X+Y C)X*Y=X·YD)X*Y=(X·Y)(mod5)(其中,-,+,·分别为减法、加法和乘法运算)(5)设p,q为两个命题,对于"p→q"的逻辑涵义,下面的哪些叙述是准确的?_____。

Ⅰ.如果p,则qⅡ.p仅当qⅢ.p当qⅣ.q是p的充分条件A)Ⅰ和Ⅱ B)Ⅲ和Ⅳ C)Ⅱ和Ⅳ D)Ⅰ和Ⅲ(6)在谓词逻辑中,令F(x)表示x是火车,G(y)表示y表示汽车,L(x,y)表示, "并不是所有的火车比所有的汽车快"的符号表示中哪些是准确的?_____。

(2分)Ⅰ. x y(F(x)∧G(y)→L(x,y))Ⅱ. x y(F(x)∧G(y)∧L(x,y))Ⅲ. x y(F(x)∧G(y)→L(x,y))A)仅Ⅰ B)仅Ⅱ C)Ⅰ和Ⅱ D)都不对(7)设R是集合A={a,b,c,d}上的二元关系,R={,,,,,}下面哪些命题为真?_____。

2019年计算机等级考试四级笔试练习题

2019年计算机等级考试四级笔试练习题一、选择题1、8位二进制原码表示整数的范围是A）0 ~ + 128 B）- 128 ~ + 128C）0 ~ + 127 D）- 127 ~ + 1272、设有下三角矩阵A[0..10,0..10]，按行优先顺序存放其非零元素，每个非零元素占两个字节，存放的基地址为100，则元素[5，5]的存放地址为A）110 B）120 C）130 D）1403、下列命题中为简单命题的是A）张葆丽和张葆华是亲姐妹B）张明和张红都是大学生C）张晖或张旺是河北省人D）王际广不是工人4、在多道程序设计环境中，将指令系统中的指令分成特权指令和非特权指令。

在下列指令中，哪个不是特权指令？A）启动设备执行I/O操作指令B）访管指令C）置中断向量指令D）修改程序状态字指令5、软件开发过程中，往往会出现错误，经验证明最容易产生错误的阶段是A）详细设计 B）需求分析 C）编码 D）概要设计6、设相关系R = (A,B,C)，和关系代数表达式：Ⅰ. πA,C（σB=5（R））Ⅱ. σB=5 (πA , C (R))Ⅲ. σA ,C(πB=5 (R))上述关系代数表达式中，与SQL语句select distinct A,C from R where B = 5等价的是A）都等价 B）Ⅲ C）Ⅱ D）Ⅰ7、寄存器窗口重叠技术是RISC的关键技术，这项技术能很好地支持过程调用和返回操作。

这里所谓的重叠是指A）高位寄存器与局部寄存器重叠B）高位寄存器与低位寄存器重叠C）全局寄存器与局部寄存器重叠D）全局寄存器与高位寄存器重叠8、确定网络拓朴构型是网络系统设计的重要内容之一。

网络拓朴对网络系统的影响主要表现在哪几个方面？Ⅰ.网络性能Ⅱ.系统可靠性Ⅲ.网络体系结构Ⅳ.通信费用A) Ⅰ和Ⅱ B) Ⅰ、Ⅱ和Ⅲ C）Ⅰ、Ⅱ和Ⅳ D）全部9、In which phase of the software engineering process is the Software Requirements Specification developed?A)definition phase B)engineering phaseC)maintenance phase D)development phase10、For relation R where primary key contains multiple attributes,no non-key attribute should be functionally dependent on a part of the primary key.This relation R is at least inA)1NF B)2NF C)3NF D)BCNF11、Most frequently used algorithm for page replacement isA)LRU B)FIFO C)OPT D)PPT12、The following three concepts are essential to the OSI model：service,interface andA)networks B)applications C)protocols D)layers二、论述题当前，绝大部分计算机系统都支持虚拟页式地址转换机制。

2019年全国计算机等级考试四级笔试选择试题7

2019年全国计算机等级考试四级笔试选择试题7(26) 判定表和判定树是数据流图中用以描述加工的工具，它常描述的对象是_____。

A) 逻辑判断 B) 层次分解 C) 操作条目 D) 组合条件(27) 模块独立性是软件模块化所提出的要求，衡量模块独立性的度量标准则是模块的_____。

A) 抽象和住处隐蔽 B) 局部化和封装化C) 内聚性和耦合性 D) 激活机制和控制方法(28) 软件设计一般分为总体设计和详细设计，它们之间的关系是_____。

A) 全局和局部 B) 抽象和具体C) 总体和层次 D) 功能和结构(29) 软件的复审是**软件质量的必要手段，下述Ⅰ.软件的可追溯性Ⅱ.软件的可维护性Ⅲ.方案的可选择性Ⅳ.接口的明确性哪些是软件复审时所涉及的技术内容？_____。

A) Ⅰ和Ⅱ B) Ⅰ、Ⅱ和Ⅲ C) Ⅱ和Ⅲ D) 都准确(30) 原型化方法是软件开发中一类常用的方法，它与结构化方法相比较，更需要_____。

A) 明确的需求定义 B) 完整的生命周期C) 较长的开发时间 D) 熟练的开发人员(31) 软件测试是软件开发的重要环节，而实行软件测试的目的是_____。

A) 证明软件错误不存有 B) 证明软件错误的存有C) 改正程序所有的错误 D) 发现程序所有的错误(32) 软件维护是**软件正常、有效运行的重要手段，而软件的下述特性：Ⅰ.可测试性Ⅱ.可理解性Ⅲ.可修改性Ⅳ.可移植性哪个（些）有利于软件的维护？_____。

A) 只有Ⅰ B) Ⅱ和Ⅲ C) Ⅰ、Ⅱ和Ⅲ D) 都有利(33) 数据库的三级模式结构由外模式、模式和内模式组成，它适合于哪个（些）类型的数据库？_____。

Ⅰ. 关系型数据库Ⅱ. 层次型数据库Ⅲ. 网状型数据库A) 只有Ⅰ B) Ⅰ和Ⅱ C) Ⅱ和Ⅲ D) 都适合(34) 设关系R和关系S的元素分别是3和4，关系T是R与S的笛卡尔积，即：T=R>×S，则关系T的元数是_____。

2019年全国计算机等级考试四级笔试试题及答案6

2019年全国计算机等级考试四级笔试试题及答案6二、论述题(四个论述题可任选其一，并只选其一，多选无效，满分30分。

)论述题的答题必须用蓝、黑色钢笔或圆珠笔写在论述题答题纸的相对应位置上，否则无效。

论述题1当前，绝大部分计算机系统都支持虚拟页式地址转换机制。

试回答下列问题：1、页式存储管理方案中，用户地址空间怎样划分？内存地址空间怎样划分？内存分配过程是怎样的？（10分）2、页表应设计哪些数据项，每个数据项的作用是什么？（10分）3、页式存储管理方案中，地址映射机制需要哪些寄存器的支持？为了加快地址映射速度，需要采取什么措施？该措施的作用是什么？（10分）论述题2软件维护是软件生命周期的重要组成，而影响维护的因素较多，除了人员因素、技术因素和管理因素外，还有程序自身的因素，具体影响因素可归纳为：1）软件系统的规模；2）软件系统的年龄；3）软件系统的结构。

试回答以下问题：1、给出上述三项因素的解释，阐述“规模”、“年龄”和“结构”的具体含义。

（10分）2、扼要分析影响维护工作量的因素，即分析可能增加工作量的因素和可能减少维护工作量的因素。

（10分）3、简单叙述软件可维护性度量的含义。

（10分）论述题3为学校中学生选课管理这个现实问题实行数据库模式设计。

根据调查分析，确定它的属性集合为：U={S #，C#，SNAME，CNAME，TEACHER，GRADE，SD}下面给出两种确定的模式设计方案：方案一：只有一个关系模式：R（S#，C#，SNAME，CNAME，TEACHER，GRADE，SD）方案二：如果根据属性之间存有的联系或相关性，建立如下三个关系：S（S#，SNAME，SD），C（C#，CNAME，TEACHER），SC（S#，C#，GRADE）1、试分析这两种模式设计方案各自的优缺点。

（26分）2、通常情况下你认为哪种方案更“好”些？请说明理由。

（4分）论述题4在实际的网络运行环境中，数据备份与恢复功能是非常重要的。

2019年12月四级考试真题及参考答案完整版

2019年12月四级考试真题及参考答案完整版（第一套）Part Ⅰ WritingDirections: For this part, you are allowed 30 minutes to write a letter to a foreign friend who wants to learn Chinese. Please recommend a university to him. You should write at least 120 words but no more than 180 words.【参考范文】Dear Lucy,I am delighted to hear that you are going to learn Chinese in a Chinese university. Since you have asked for my advice about choosing which university, I will try to give you some useful suggestions here.It is well known that Peking University is a great place to learn Chinese. There are several factors accounting for this choice and the following are the most typical ones. First and foremost, Peking University is one of the top universities in China and the birthplace of many great minds. Therefore, it can provide high-quality teaching resources, which is essential for a foreigner learner.In addition, Beijing is the capital of China and there are various historic buildings. They provide foreign students a good chance to know Chinese culture and history.I hope you will find these suggestions helpful and wish you all the best.Yours,Li MingPart Ⅱ Listening ComprehensionSection AQuestions l and 2 are based on the news report you have just heard.1.A）Many facilities were destroyed by a wandering cow.B）A wandering cow knocked down one of its fences.C）Some tourists were injured by a wandering cow.D）A wandering cow was captured by the police.2. A）It was shot to death by a police officer.B）It found its way back to the par k’s zoo.C）It became a great attraction for tourists.D）It was sent to the animal control department.Questions 3 and 4 are based on the news report you have just heard.3. A）It is the largest of its kind.B）It is going to be expanded.C）It is displaying more fossil specimens.D）It is staring an online exhibition.4. A）A collection of bird fossils from Australia.B）Photographs of certain rare fossil exhibits.C）Some ancient wall paintings from Australia.D）Pictures by winners of a wildlife photo contest.Questions 5 to 7 are based on the news report you have just heard.5. A）Pick up trash.B）Amuse visitors.C）Deliver messages.D）Play with children.6. A）They are especially intelligent.B）They are children’s favorite.C They are quite easy to tame.D）They are clean and pretty.7. A）Children may be harmed by the rooks.B）Children may be tempted to drop litter.C）Children may contract bird diseases.D）Children may overfeed the rooks.Section BQuestions 8 to 11 are based on the conversation you have just heard.8. A）It will be produced at Harvard University.B）It will be hosted by famous professors.C）It will cover different areas of science.D）It will focus on recent scientific discoveries.9. A）It will be more futuristic.B）It will be more systematic.C）It will be more entertaining.D）It will be easier to understand.10. A）People interested in science.B）Youngsters eager to explore.C）Children in their early teens.D）Students majoring in science.11. A）Offer professional advice.B）Provide financial support.C）Help promote it on the Internet.D）Make episodes for its first season.Questions 12 to 15 are based on the conversation you have just heard.12. A）Unsure.B）Helpless.C）Concerned.D）Dissatisfied.13. A）He is too concerned with being perfect.B）He loses heart when faced with setbacks.C）He is too ambitious in achieving goals.D）He takes on projects beyond his ability.14. A）Embarrassed.B）Unconcerned.C）Miserable.D）Resentful.15. A）Try to be optimistic whatever happens.B）Compare his present with his past only.C）Always learn from others’ achievements.D）Treat others the way he would be treated.Section CQuestions 16 to 18 are based on the passage you have just heard.16. A）They have a stronger sense of social responsibility.B）They are more likely to succeed in the humanities.C）They are more likely to become engineers.D）They have greater potential to be leaders.17.A）Praise girls who like to speak up frequently.B）Encourage girls to solve problems on their own.c）Insist that boys and girls work together more.D）Respond more positively to boys’ comments.18. A）Offer personalized teaching materials.B）Provide a variety of optional courses.C）Place great emphasis on test scores.D）Pay extra attention to top students.Questions 19 to 21 are based on the passage you have just heard.19. A）It often rains cats and dogs.B）It seldom rains in summer time.C）It does not rain as much as people think.D）It is one of the most rainy cities in the US.20. A）They drive most of the time.B）The rain is usually very light.C）They have got used to the rain.D）The rain comes mostly at night.21. A）It has a lot of places for entertainment.B）It has never seen thunder and lighting.C）It has fewer cloudy days than any other coastal city.D）It has mild weather both in summer and in winter.Questions 22 to 25 are based on the passage you have just heard.22. A）It occurs when people are doing a repetitive activity.B）It results from exerting one’s muscles continuously.C）It happens when people engage in an uncommon activity. D）It comes from staining one’s muscles in an unusual way.23. A）Blood flow and body heat increase in the affected area. B）Body movements in the affected area become difficult.C）They begin to make repairs immediately.D）They gradually become fragmented.24. A）About one week.B）About two days.C）About ten days.D）About four weeks.25. A）Apply muscle creams.B）Drink plenty of water.C）Have a hot shower.D）Take pain-killers.Part Ⅲ Reading ComprehensionSection AQuestions 26 to 35 are based on the following passage.Finally, some good news about airplane travel. If you are on a plane with a sick passenger, you are unlikely to get sick. That is the 26 of a new study that looked at how respiratory （呼吸道）viruses 27 on airplanes. Researchers found that only people who were seated in individual - had a high risk of catching the illness. All other passengers had only a very 28 chance of getting sick according to the findings. Media reports have not necessarily presented.29 information about the risk of getting infected on an airplane in the past. Therefore , these new findings should help airplane passengers to feel less 30 to catching respiratory infections while traveling by air.Prior to the new study. litter was known about the risks of getting 31 infected by common respiratory viruses, such as the flu or common cold, on an airplane, the researchers said. So, to 32 the risks of infection, the study team flew on 10 different 33 in the US. 34 side of a person infected with flu, as well as those sitting one roe in font of or behind this individual, had about an 80 person chance of getting sick. But other passengers were 35 safe from infection. They had a less than 3 percent chance of catching the flu.A）accurate B）conclusion C）directlyD）either E）evaluate F）explorationsG）flights H）largely I）nearbyJ）respond K）slim L）spreadM）summit N）vividly O）vulnerable【参考答案】26-30 BLKAO31-35 CEGDHSection BA South Korean city designed for the future takes on a life of its ownA）Getting around a city is one thing —and then there’s the matter of getting from one city to another. One vision of the perfect city of the future: a place that offers easy access to air travel.In 2011, a University of North Carolina business professor named John Kasarda published a book called Aerotropolis: The Way We’ll Live Next. Kasarda says future cities should be built intentionally around or near airports. The idea, as he has put it, is to offer businesses “rapid, long-distance connectivity on a massive scale.”B）“The 18th century really was a waterborne （水运的）century, the 19th century a rail century. the 20th century a highway, car, truck century一and the 21st century will increasingly be an aviation century, as the globe becomes increasingly connected by air,” Kasarda says. Songdo, a city built from scratch in South Korea, is one of Kasarda’s prime examples. It has existed for just a few years.“ From the get-go, it was designed on the basis of connectivity and competitiveness,”says Kasada. “The government built the bridge directly from the airport to the Songdo International Business District. And the surface infrastructure was built in tandem with the new airport.”C）Songdo is a ston e’s throw from South Korea’s Incheon Airport, its main international hub （枢纽）. But it takes a lot more than a nearby airport to be a city of the future. Just building a place as an “international business district” doesn’t mean it will become one. Park Yeo n Soo conceived （构想）this city of the future back in 1986. He considers Songdo his baby. “I am a visionary,” he says. Thirty years after he imagined the city, Park’s baby is close to 70 percent built, with 36.000 people living in the business district and 90,000 residents in greater Songdo. It’s about an hour outside Seoul, built on reclaimed tidal flats along the Yellow Sea, There’s a Coast Guard building and a tall trade tower, as well as a park, golf course and university.D）Chances are you’ve actually seen this place. Songdo appears in the most famous music video ever to come ou of South Korea. “Gangnam Style” refers to the fashionable Gangnam district in Seoul. But some of the video was filmed in Songdo.“I don’t know if you remember, there was a scene in a subwaystation. That was not Gangnam. That was actually Songdo,” says Jung Won Son, a professor of urban development at London’s Bartlett School of Planning, “Part of the reason to shoot there is that it’s new and nice.”E）The city was supposed to be a hub for global companies, with employees from all over the world. But hat’s not how it has turned out. Songdo’s reputation is as a futuristic ghost town. But the reality is more complicated. A bridge with big, light-blue loops leads into the business district. In the center of the main road, there’s a long line of flags of the world. On the corner, there’s a Starbucks and a 7-Eleven--all of the international brands that you see all over the world nowadays.F）The city is not empty. There are mothers pushing strollers, old women with walkers -- even in the middle of the day. when it’s 90 degrees out. Byun Young-Jin chairs the Songdo real estate association and started selling property here when the first phase of the city opened in 2005. He says demand has boomed in the past couple of years. Most of his clients are Korean. In fact, the developer says, 99 percent of the homes here are sold to Koreans. Young families move here because the schools are great. And that’s the problem: Songdo has become a popular Korean city 一more popular as a residential area than a business one. It’s not yet the futuristic international business hub that planners imagined. “It’s a great place to live. And it’s becoming a great place to work,” says Scott Summers, the vice presiden t of Gale International, the developer of the city. The floor-to-ceiling windows of his company’s officesoverlook Songdo Central Park, with a canal full of kayaks and paddle boats. Shimmering （闪烁的）glass towers line the canal’s edge.G）“What’s happened i s, because we focused on creating that quality of life first, which enabled the residents to live here, what has probably missed the mark is for companies to locate here,” he says. “There needs to be strong economic incentives.” The city is still unfinishe d, and it feels a bit like a theme park. It doesn’t feel all that futuristic. There’s a high-tech underground trash disposal system. Buildings are environmentally friendly. Everybody’s television set is connected to a system that streams personalized language or exercise classes.H）But Star Trek this is not. And to some of the residents, Songdo feels hollow. “I’m, like, in prison for weekdays. That’s what we call it in the workplace,” says a woman in her 20s. She doesn’t want to use her name for fear of be ing fired from her job. She goes back to Seoul every weekend. “I say I’mprison-breaking on Friday nights.” But she has to make the prison break in her own car. There’s no high-speed train connecting Songdo to Seoul, just over 20 miles away.I）The man who first imagined Songdo feels frustrated. too. Park says he built South Korea a luxury vehicle, “like Mercedes or BMW. It’s a good car now. But we’re waiting for a good driver to accelerate.” But there are lots of other good cars out there, too. The world is dotted with futuristic, high-tech cities trying to attract the biggest international companiesJ）Songdo’s backers contend that it’s still early, and business space is filling up—about 70 percent of finished offices are now occupied. Brent Ryan, who teaches urban design at MIT, says Songdo proves a universal principle. “There have been a lot of utopian （乌托邦的）cities in history. And the reason we don’t know about a lot of them is that a lot of them have vanished entirely.” In other words, when it comes to cities—or anything else—it is hard to predict the future.36. Songdo’s popularity lies more in its quality of life than its business attraction.37. The man who conceives Songdo feels disappointed because it has fallen short of his expectations.38. A scene in a popular South Korean music video was shot in Songdo.39. Songdo still lacks the financial stimulus for businesses to set up shop there.40. Airplanes will increasingly become the chief means of transportation, according to a professor.41. Songdo has ended up different from the city it was supposed to be.42. Some of the people who work in Songdo complain about boredom in the workplace.43. A business professor says that a future city should have easy access to international transportation.44. Acording to an urban design professor, it is difficult for city designers to foresee what happen in the future.45. Park Yeon So. Who envisioned Songdo, feels a parental connection with the city.【参考答案】36-40 FIDGB41-45 EHAJCSection CPassage OneQuestions 46 to 50 are based on the following passage.The fifth largest city in the US passed a significant soda tax proposal that will levy （征税）1.5cents per liquid ounce on distributors.Philadelphia’s new measure was approved by a 13 to 4 city council v ote. It sets a new bar for similar initiatives across the county. It is proof that taxes on sugary drinks can win substantial support outside super-liberal areas. Until now, the only city to successfully pass and implement a soda tax was Berkeley, California, in 2014.The tax will apply to regular and diet sodas, as well as other drinks with added sugar, such as Gatorade and iced teas. It’s expected to raise $410 million over the next five years, most of which will go toward funding a universalpre-kindergarten program for the city.While the city council vote was met with applause inside the council room, opponents to the measure, including soda lobbyists made sharp criticisms and a promise to challenge the tax in court.“The tax passed today unfairly singl es out beverages—including low- andno-calorie choices,” said Lauren Kane, spokeswoman for the American Beverage Association. “But most importantly, it is against the law. So we will side with the majority of the people of Philadelphia who oppose this tax and take legal action to stop it.”An industry backed anti-tax campaign has spent at least $4 million on advertisements. The ads criticized the measure. characterizing it as a“grocery tax.”Public health groups applauded the approved tax as a step toward fixing certain lasting health issues that plague Americans. “The move to recapture a small part of the profits from an industry that pushes a product that contributes to diabetes, obesity and heart disease in poorer communities in order to reinvest in those communities will sure be inspirational to many other places,” said Jim Krieger, executive director of Healthy Food America. “Indeed, we are already hearing from some of them. It’s not just Berkeley’ anymore.”Similar measures in California’s Albany, Oakla nd, San Francisco and Colorado’s Boulder are becoming hot-button issues Health advocacy groups have hinted that even more might be coming.46. What does the passage say about the newly-approved soda tax in Philadelphia?A）It will change the lifestyle of many consumers.B）It may encourage other US cities to follow suit.C）It will cut soda consumption among low-income communities.D）It may influence the marketing strategies of the soda business.47. What will the opponents probably do to respond to the soda tax proposal? A）Bargain with the city council.B）Refuse to pay additional tax.C）Take legal action against it.D）Try to win public support.48. What did the industry-backed anti-tax campaign do about the soda tax proposal?A）It tried to arouse hostile feelings among consumers.B）It tried to win grocers’ support against the measure.C）It kept sending letters of protest to the media.D）It criticized the measure through advertising.49. What did public health groups think the soda tax would do?A）Alert people to the risk of sugar-induced diseases.B）Help people to fix certain long-time health issues.C）Add to the fund for their research on diseases.D）Benefit low-income people across the country.50. What do we learn about similar measures concerning the soda tax in some other cities?A）They are becoming rather sensitive issues.B）They are spreading panic in the soda industry.C）They are reducing the incidence of sugar-induced diseases.D）They are taking away lot of profit from the soda industry.Passage TwoQuestions 51 to 55 are based on the following passage.Popping food into the microwave for a couple of minutes may seem utterly harmless, but Europe’s stock of these quick-cooking ovens emit as much carbon as nearly 7 million cars, a new study has found. And the problem is growing. With costs falling and kitchen appliances becoming “status” items, owners are throwing away microwaves after an average of eight years. This is pushing sales of new microwaves which are expected to reach 135 million annually in the EU by the end of the decade.A study by the University of Manchester calculated the emissions of CO2—the main greenhouse gas responsible for climate change—at every stage of microwaves, from manufacture to waste disposal. “It is ele ctricity consumption by microwaves that has the biggest impact on the environment,” say the authors. The authors also calculate that the emissions from using 19 microwaves over a year are the same as those from using a car. According to the same study, efforts to reduce consumption should focus on improving consumer awareness and behaviour. For example, consumers could use appliances in a more efficient way by adjusting the time of cooking to the type of food.However, David Reay, professor of carbon management, argues that, although microwaves use a great deal of energy, their emissions are minor compared to those from cars. In the UK alone, there are around 30 million cars. These cars emit more than all the microwaves in the EU. Backing this up, recent data show that passenger cars in the UK emitted 69 million tons of CO2 in 2015. This is 10 times the amount this new microwave oven study estimatesfor annual emissions for all the microwave ovens in the EU. Further, the energy used by microwaves is lower than any other from of cooking. Among common kitchen appliances used for cooking, microwaves are the most energy efficient, followed by a stove and finally a standard oven. Thus, rising microwave sales could be seen as a positive thing.51. What is the finding of the new study?A）Quick-cooking microwave ovens have become more popular.B）The frequent use of microwaves may do harm to our health.C）CO2 emissions constitute a major threat to the environment.D）The use of microwaves emits more CO2 than people think.52. Why are the sales of microwaves expected to rise?A）They are becoming more affordable.B）They have a shorter life cycle than other appliances.C）They are getting much easier to operate.D）They take less time to cook than other appliances.53. What recommendation does the study by the University of Manchester make?A）Cooking food of different varieties.B）Improving microwave users’ habits.C）Eating less to cut energy consumption.D）Using microwave ovens less frequently.54. What does Professor David Reay try to argue?A）There are far more emissions from cars than from microwaves.B）People should be persuaded into using passenger cars less often.C）The UK produces less CO2 than many other countries in the EU.D）More data are needed to show whether microwaves are harmful.55. What does Professor David Reay think of the use of microwaves?A）It will become less popular in the coming decades.B）It makes everyday cooking much more convenient.C）It plays a positive role in environmental protection.D）It consumes more power than conventional cooking.Part Ⅳ Translation中国家庭十分重视孩子的教育。

2019四级真题12月第二套

2019四级真题12月第二套1.关于晶体三极管描述不正确的有？（） [单选题] *A. 晶体三极管有三只引脚，分别叫做 B(基极)、C(集电极)和 E(发射极)B. 晶体三极管根据结构不同，分为 NPN 和 PNP 两种类型C. 晶体三极管有三只引脚，分别叫做 B(基极)、P(阳极)和 N(阴极)(正确答案)D. 晶体三极管可用于开关电路和放大电路2.在流程图中表示判断条件的是？ [单选题] *A. B.D.C.(正确答案)3.想要让一个变量 a 每次都增大到自己的二倍，下列程序正确的是?（） [单选题] *A. a=2a;B. 2a;C. a=2*a;(正确答案)D. a==2*a;4.下列关于顺序结构说法正确的是？（） [单选题] *A. 顺序结构的执行顺序是自上而下，依次执行(正确答案)B. 顺序结构的程序设计是最复杂的C. 顺序结构中只要没有延时函数或模块，程序都是同时执行的D. 顺序结构是指在程序中需要反复执行某个功能而设置的一种程序结构5.下列那个选项中属于分支结构？（） [单选题] *A. for 语句B. switch 语句(正确答案)C. while 语句D. do while 语句6.关于 PWM，以下说法正确的有？（） [单选题] *A. 当占空比为 10%时，等效输出电压为 4.5VB. 可以利用 PWM 管脚实现模拟信号输入C. PWM 是指在数字系统中，通过调整占空比来实现模拟输出(正确答案)D. UNO 主控板，A0-A5 管脚具有 PWM 模拟输出功能7.二进制数 11+1=？（） [单选题] *A. 100(正确答案)B. 101C. 110D. 1118.下列关于 if 语句说法正确的是？（） [单选题] *A. if 语句只能适合单分支结构B. if 语句可以变形为 if-else 或者 if-else if-else(正确答案)C. 使用 if 语句就可以实现重复执行某一段功能D. if 语句的执行顺序是自上而下，依次执行9.如下图所示分支结构中说法正确的是？[单选题] *A. 该 switch 中没有 default 所以结构是错误的B. 当 a==1 时，先执行语句 1，再执行语句 2；再执行语句 3；再执行语句 4C. 当 a==2 时，先执行语句 2，再执行语句 3；再执行语句 4D. 当 a==3 时，执行语句 3 后，跳出{}，这段程序执行完毕(正确答案)10.执行下列所示程序，输出 a 为?[单选题] *A. a=3(正确答案)B. a=2C. a=1D. a=011.下列分支结构中格式正确的是？ [单选题] *A.(正确答案)B.C.D.12. pinMode(pin,mode)函数设置数字引脚的工作模式，以下说明正确的有？（）[单选题] *A. 引脚的工作模式有：INPUT、OUTPUT 两种B. 引脚的工作模式有：INPUT、OUTPUT、INPUT_PULLUP 三种(正确答案)C. 引脚的工作模式有：INPUT、OUTPUT、HIGH 三种D. 引脚的工作模式有：HIGH、LOW 两种13. analogWrite(pin,val)函数中，val 的值的说明不正确的有？（） [单选题] *A. Val 值的范围 0-255B. Val 值为 255 时，引脚完全打开，管脚输出高电平C. Val 值为 255 时，引脚完全关闭，管脚输出低电平(正确答案)D. 当 val 值为 255 时，和 digitalWrite(pin,HIGH)效果一致14.下列关于变量类型的说法正确的是?（） [单选题] *A. float 代表的是浮点型，它可以保留到小数点后七位B. int 代表的是整数型，可是表示真分数C. char 表示的字符型，也可以表示一个字节大小的数字(正确答案)D. bool 是布尔型，这种类型也可以取 0-255 的整数15.下列关于程序三种基本结构说法正确的是？（） [单选题] *A. 顺序结构可以通过判断不同的情况，执行不同的内容B. 选择结构又称作分支结构，这种结构可以实现一定功能的循环C. 循环结构可以实现重复执行某个功能(正确答案)D. 只有循环结构中会用到 break16.获取电位器模块的返回值，以下选择正确的是？（） [单选题] *A. digitalRead(A0)B. digitalRead(3)C. digitalWrite(5)D. analogRead(A0)(正确答案)17.关于 pulseIn()函数，下列说法正确的是？（） [单选题] *A. pulseIn()函数用于向管脚输出高低电平B. pulseIn()函数用来读取一个管脚的脉冲(HIGH 或 LOW)(正确答案)C. pulseIn()函数只能读取管脚的高电平脉冲D. pulseIn()函数的返回值是 0 或者 118.如下图所示变量运算，说法正确的是?[单选题] *A. 程序结束后，a 的值为 2.5B. 程序结束后，a 的值为 2(正确答案)C. 变量 c 为整数型；a 和 b 为浮点型D. 程序结束后，b 的值为 419.关于多分支结构说法正确的是？（） [单选题] *A. 当表达式 1 成立时，执行语句 1；再执行语句 2，语句 3B. 当表达式 1 不成立时，执行语句 2；不执行语句 1，语句 3C. 表达式 1 成立，表达式 2 也成立时，执行语句 2D. 表达式 1 不成立，表达式 2 成立时，执行语句 2；不执行其他语句(正确答案)20.关于 setup()函数和 loop()函数，以下说法正确的是？（） [单选题] *A. 程序编写时，setup()函数和 loop()函数可以缺失B. setup()函数里面的程序，在程序执行时通常放置程序的初始化程序(正确答案)C. loop()函数里面的程序，在程序运行时只运行一次,通常放置主执行程序D. 程序运行时，先运行 loop()函数内的程序，然后运行 setup()函数内的程序21.下列选项中关于 break 和 continue 说法正确的是？（） [单选题] *A. 在循环结构中 break 是结束本次循环，continue 是结束整个循环B. 在循环结构中 break 和 continue 用于结束整个循环C. 在循环结构中 break 和 continue 是结束本次循环D. 在循环结构中 break 是结束整个循环，continue 是结束本次循环(正确答案)22.下列选项中，说法不正确的是？（） [单选题] *A. 日常生活中如果路口遇到红灯，需要停车等待；如果是绿灯，则要开车通过；这段描述在程序中，属于分支结构B. 自动门看到人可以自动开启，在程序中属于分支结构(正确答案)C. S 弯巡线小车是利用 while 循环结构判断是否遇到黑线的D. 使用蜂鸣器播放声音可以使用循环结构23.使用 UNO 主控板控制小车的速度连续变化，可以使用引脚？（） [单选题] *A. 0B. 1C. 3(正确答案)D. A024.下列程序中，没有实现了让变量 a 自动加 1 的效果的是?（） [单选题] *A. a+1;(正确答案)B. a=a+1;C. a+=1;D. a++;25.下列关于变量的说法正确的是?（） [单选题] *A. 变量可以随时改变(正确答案)B. 在声明变量时，必须赋予初始值C. 程序中变量不仅值可以变化，名称可以随意变化D. 程序中变量只能用于计数26.下列选项中关于循环结构说法错误的是？（） [单选题] *A. 循环结构可以减少源程序重复书写的工作量，用来描述重复执行某段算法的问题B. 循环结构中一般会标明循环的条件，不是无止境的循环C. 循环结构中，if 语句最常用(正确答案)D. 循环结构 while 和 do while 的区别是:while 先判断循环条件再执行内容；do while 则先执行内容再判断循环条件27.如下图所示循环结构，循环的次数为？[单选题] *A. 3(正确答案)B. 2C. 1D. 028.下列程序书写格式正确的是？ [单选题] *A. B.C. D.(正确答案)29.下列选项中不属于程序三种基本结构的是？（） [单选题] *A. 顺序结构B. 选择结构C. 总线结构(正确答案)D. 循环结构30.下列关于变量定义正确的是?（） [单选题] *A. float a=0;(正确答案)B. int 2a=0;C. int a*=0;D. int a=0;b=0;31.如下列程序中，书写格式正确的有？ *A.B.(正确答案)C.(正确答案)D.(正确答案)32.下列选项中说法正确的是？（） *A. float 代表的是浮点型，它可以保存七位有效数字(正确答案)B. 在声明变量时，可以根据需要赋初值或者不赋初值(正确答案)C. a--，指的是将变量自动减 1(正确答案)D. a*3，指的是将变量扩大三倍33.如果下图所示变量运算，程序结束后输出值正确的是？*A. a=2(正确答案)B. a=2.5C. b=3.5(正确答案)D. b=4.534.下列关于变量的运算说法错误的是？（） *A. a++;指的是将变量 a 自动加 1B. a--;指的是将变量自动减 2(正确答案)C. a=a+1;这个等式不成立(正确答案)D. a=a*2;指的是将变量 a 增大 2(正确答案)35. 关于下图分支结构说法错误的是？*A. 满足表达式执行语句 2,不满足执行语句 1(正确答案)B. 满足表达式执行语句 1,不满足执行语句 2C. 满足表达式先执行语句 1，再执行语句 2(正确答案)D. 不满足表达式先执行语句 2 ，再执行语句 1(正确答案)36.自定义函数可以将简化复杂的程序，或者减少工作量。

2019年全国计算机等级考试四级笔试选择试题2

2019年全国计算机等级考试四级笔试选择试题2(26)使用视图会给系统带来很多优点，但下面的列出的优点中，哪一条不是使用视图的优点？____。

A)提升数据独立性B)提升数据安全性C)使操作简便D)减少存储空间(27)Foxpro允许在同一幅屏幕上显示多个窗口，但只有一个窗口是活动的，这个活动窗口是？____。

A)鼠标指针所在的窗口B)窗口的标题以高亮度显示的窗口C)含有主菜单的窗口D)含有对话框的窗口(28)数据库的安全性是指保护数据库，以防止不合法的使用而造成的数据泄露、更改或破坏，以下列出的措施中，哪一种措施不属于实现安全性的措施？____。

（2分）A)数据备份B)授权规则C)数据加密D)用户标识和鉴别(29)表示概念模型的有效工具之一是E——R图，考虑下面的E——R图，若转换为关系模式，一般应能转换成多少个关系模式？____。

A)只有一个B)只有二个C)有三个D)有三个以上(30)在关系数据库中，要求关系中的元组在组成主键的属性上不能有空值。

这是遵守：____。

（2分）A)可靠性规则B)安全性规则C)实体完整性规则D)引用完整性规则(31)关系R和S定义如下：Ｒ：Ｓ：┌──┬──┬──┐┌─┬─┐│A │B │C ││C │D │├──┼──┼──┤├─┼─┤│1 │2 │3 ││3 │1 ││4 │5 │6 ││6 │2 ││7 │8 │9 ││││执行操作的R S的结果是(其中为自然连接操作符)(2分)┌──┬──┬──┬─┐┌──┬──┬─┬──┬──┐A)│A │B │C │D │B)│A │B │C│C │D │├──┼──┼──┼─┤├──┼──┼─┼──┼──┤│1 │2 │3 │1 ││1 │2 │3│3 │1 ││4 │5 │6 │2 ││4 │5 │6│6 │2 │┌──┬──┬──┬─┐┌──┬──┬──┐C)│A │B │C │D │D)│C │C │D │├──┼──┼──┼─┤├──┼──┼──┤│1 │2 │3 │1 ││3 │3 │1 ││4 │5 │6 │2 ││6 │6 │2 ││7 │8 │9 │0 ││9 │0 │0 │(32)下面列出的技术中，哪一个(些)是ORACLE RDBMS用来实现分布式数据库管理的？____。

2019年计算机考试四级笔试论述模拟试题及答案

2019年计算机考试四级笔试论述模拟试题及答案二、论述题论述题1按规范设计的方法将数据库设计分为六个阶段：1 需求分析。

2概念结构设计。

3 逻辑结构设计。

4 数据库物理设计。

5 数据库实施。

6 数据库运行和维护。

针对关系数据库设计的逻辑结构设计，回答下述问题：1、逻辑设计的基本任务?2、逻辑设计过程中，如何将E—R 模型向关系数据模型转换?3、关系数据库逻辑设计的步骤和内容?论述题2模块独立性是由内聚性和耦合性两个定性指标来度量的。

回答下列问题：1. 什么是内聚性?什么是耦合性?2. 内聚分为哪几类?耦合分为哪几类?3. 什么是时间内聚?什么是公共耦合?论述题3：请说明操作系统作业管理的功能?作业调度算法是指按照什么样的原则来选择作业并投入运行，调度算法的合理性直接影响系统的效率，作业调度算法有哪些? 对算法的选择需要考虑哪些问题?论述题4：在数据链路层，HDLC信息帧的N(S)、N(R)域能够实现流量控制，滑动窗口也能够实现流量控制，分别依据HDLC 信息帧及滑动窗口，分别讨论下列问题：(1) 信息帧中如果N(S)=7，N(R)=4，问发送方不必等待确认能够连续发送多少帧?接收方下一预期接收的帧的序号?(2) 滑动窗口中，发送窗口的大小WT=2 ，接收窗口的大小WR=1，则发送方不必等待确认能够连续发送多少帧?接收方同时能接收多少帧?(3)若N(S)采用3 位二进制编码时，发送窗口的值是多少?二、论述题论述题1 参考答案1、逻辑设计的目的是，从概念模型导出特定的DBMS 能够处理的数据库的逻辑结构(数据库的模式和外模式)，这些模式在功能、性能、完整性和一致性约束及数据库可扩充性等方面均应满足用户提出的要求。

2、E-R模型向关系数据模型的转换规则是：(l) 一个实体类型转换成一个关系模式，实体的属性就是关系的属性，实体的键就是关系的键。

(2)一个联系类型转换成一个关系模式，参与该联系类型的各实体的键以及联系的属性转换成关系的属性。

2019年9月计算机等考四级数据库工程师笔试真题和答案

2008年9月计算机等级考试四级数据库笔试一试题一、选择题(1)在数据库应用系统生命周期模型中，规划与剖析阶段的输出结果不包含A)需求规范说明书B)系统范围与界限C)可行性剖析报告D)项目计划书(2)在信息系统的需求剖析中，广为使用的DFD建模方法属于A)构造化剖析方法B)数据剖析方法C)数据抽象方法D)业务概括方法(3)不一样意出此刻最后IDEF1X图中的是A)标定型联系B)非标定型联系C)分类联系D)多对多联系(4)以下哪些属性不合适成立索引?A)常常出此刻GROUP BY字句中的属性B)常常参加连结操作的属性C)常常出此刻WHERE字句中的属性D)常常需要进行更新操作的属性(5)在数据库应用系统生命周期模型中，作为系统整体设计阶段输入的是A)技术可行性剖析报告和需求规范说明书B)软硬件选型和配置设计C)数据库应用系统系统构造设计D)应用软件整体设计(6)SQL Server 2000中，假如希望用户u1在DB1数据库中拥有查问T1表的权限，正确的受权语句是A) GRANT SELECT ON DB1(T1) TO u1B) GRANT SELECT TO u1 ON DB1(T1)C) GRANT SELECT TO u1 ON T1D) GRANT SELECT ON T1 TO u1(7)SQL Server 2000供给了好多预约义的角色，下述对于public角色说法正确的选项是A)它是系统供给的服务器级的角色，管理员能够在此中增添和删除成员B)它是系统供给的数据库级的角色，管理员能够在此中增添和删除成员C)它是系统供给的服务器级的角色，管理员能够对其进行受权D)它是系统供给的数据库级的角色，管理员能够对其进行受权(8)对于ADO对象模型中的RecordSer，下陈述法正确的选项是A)它用于定义连结的数据库名B)它用于定义数据的根源C)它是一个对象，用于在客户端内存中寄存数据查问的结果D)它是一个对象，用于在服务器端内存中寄存数据查问的结果(9)对于ADO对象模型，下陈述法正确的选项是A)它是与OLE DB同层的独立的接口集B)它是与ODBC同层的独立的接口集C)它是成立在OLE DB接口之上的高层接口集D)OLE DB是成立在ADO对象模型之上的高层接口集(10)对于UML的静态建模体制，下陈述法错误的选项是A)用例模型是将知足用户需求的所有功能表示出来的工具B)用例图用于表示系统的数据模型和功能模型C)类图显现了一组类，接口和协作以及它们之间的关系D)组件图表示系统的静态实现视图，用于对源代码、可履行程序和物理数据库等进行建模(11)对于散布式数据库的散布策略，下陈述法正确的选项是A)数据分派是对关系的操作，数据分片是对数据分派的操作B)集中式数据分派策略不便于进行数据控制C)全复制式数据分派策略靠谱性高，响应速度快，但数据冗余大，同步保护复杂D)切割式数据分派策略对全局数据控制灵巧，但对局部数据存取效率低(12)对于数据区分策略，下陈述法错误的选项是A)散列区分采纳某种散列函数，以数据的区分属性作为函数参数，计算数据应储存的磁盘序号B)范围区分依据某个属性的取值，将数据区分为n个部分，分别储存到不一样磁盘上C)范围区分有益于范围查问和点查问，但也可能会惹起数据散布不均匀及并行办理能力降落问题D)轮转法区分能保证元组在多个磁盘上的均匀分派，并拥有较高的点查问和范围查问(13)将新插入的记录储存在文件末端，并使记录随机地散布在文件物理储存空间中的文件构造是A)堆文件B)齐集文件C)索引文件D)散列文件(14)有一个事务T要更新数据库中某表列的值，DBMS在履行T时发现更新后的值高出了该列的值定义范围，所以异样停止了T。

2019年全国计算机等级考试四级笔试试题及答案5

2019年全国计算机等级考试四级笔试试题及答案5(61) If file A has the capability of 724,the samegroup’s users of file A may do____．A) read A only B) write A C) execute A D) non-operation(62) In which phase of the software engineering process is the Software Requirements Specification developed?____．A) definition phase B) engineeringC) maintenance D) development phase(63) The prototyping method is a dynamic design process,which requires people who use prototyping method to have the following capability of____．A) proficient program expertise B) immediately acquire requirementC) coordinate & organize eloquently D) handle tools smartly(64) For relation R where primary key contains multiple attributes,no non-key attribute should be functionally dependent on a part of the primary key. This relation R is at least in____．A) 1NF B) 2NF C) 3NF D) BCNF(65) Which of the following statements about object oriented databse is not correct?____．A) Each object has a unique object identity in the system.B) Encapsulation and inheritance are two important features of object oriented database.C) A subclass can inherit the attributes and methods of all its superclasses.D) A subclass includes the attributes and methods of all its subclasses.(66) Local bus can increase the data throughput. The bus that is most frequently used is____．A) VESA B) EISA C) MCA D) PCI(67) Most frequently used algorithm f or page replacement is____．A) LRU B) FIFO C) OPT D) PPT(68) The following three concepts are essential to the OSI model：service,interface and____．A) networks B) applicationsC) protocols D) layers(69) LANs can be connected by using bridges,which operate in the____．A) physical layer B) data link layerC) network layer D) transport layer(70) TCP service is obtained by having both the sender and the receiver create end points,which are called____．A) network address B）supernet addressC) socket D) IP address。

2019年全国计算机等级考试四级笔试试题及答案3

2019年全国计算机等级考试四级笔试试题及答案3(31) 软件测试的白箱测试是对软件的结构实行测试，下述Ⅰ.边缘值分析Ⅱ.语句测试Ⅲ.分支测试Ⅳ.路径测试哪个（些）是其应包括的内容？____。

A）Ⅰ B）Ⅱ和Ⅲ C）Ⅲ和Ⅳ D）Ⅱ、Ⅲ和Ⅳ(32) 软件维护一般包括：校正性维护、适合性维护、完善性维护和预防性维护，下述哪一个应属于完善性维护的内容？____。

A) 发现并改进测试阶段未发现的错误 B) 使软件系统适合新的运行环境C) 增加软件新的处理功能 D) 改良未来的软件的可靠性和可维护性(33) 用表格形式的结构表示实体类型以及实体类型之间联系的数据模型是____。

A) 关系数据模型 B) 层次数据模型C) 网状数据模型 D) 面向对象数据模型(34) 在零件-供应数据库中，有如下三个关系：供应商关系：S（供应商号，供应商名，地址）零件关系：P（零件号，零件名，颜色，重量）供应关系：SP（供应商号，零件号，数量）若要查找“红色零件的供应商名”，将涉及到关系____。

A) P和SP B) S和P C) S和SP D) S、P和SP(35) 若用如下的SQL语句创建表S：CREATE TABLE S（S# CHAR（6）PRIMARY KEY，SNAME CHAR（8）NOT NULL，SEX CHAR（2），AGE INTEGER）并且S表中已经有两行：（‘022345’，‘李明芳’，‘女’，23）和（‘021876’，‘张为’，‘男’，32）今欲向S表插入新元组：Ⅰ.（‘022345’，‘彭明芳’，‘女’，23）Ⅱ.（‘020746’，‘杨云’，NULL，NULL）Ⅲ. （‘020721’，‘张为’，‘女’，21）哪一个（些）元组能够被成功插入？____。

A) 全部B) Ⅰ和Ⅱ C) Ⅰ和Ⅲ D) Ⅱ和Ⅲ(36) 设相关系R=（A,B,C）,和关系表达式：上述关系代数表达式中，与SQL语句select distinct A,C from R where B=5 等价的是____。

2019新版四级试卷

1、 Directions： For this part,you are allowed 30 minutes to write an essay entitled The HarmofPC Games.Youshould write at least 120 words but no morethan 180 words according to the outline given gelow in Chinese.Write your essay on Amwer Sheet 1.1.很多学生迷恋电脑游戏;2.电脑游戏的危害;3.你的观点。

1、A.He refused to take Linda with them.B.He agreed to take Linda with them.C.He thought Linda should decide herself.D.He thought Linda should write something.3、A.By car.B.By bus.C.By plane.D.By train.4、A.Don’tdrink bee r.B.Drink dark beer.C.Don’t use ice.D.Boil thebeer.5、A.The teacher postponed the meeting this afternoon.B.There won’t be a test this aftemoon.C.The students will be attending the meeting.D.The students will take a test this aftemoon.6、A.If he can help her fill out a job application.B.If he can introduce her to the campus counselor.C.If he knows of any job openings with his former employer.D.If he’ll returntothe campus where he workedlast year.7、A.Someone else should make the introduction.B.Dan isn’t a very good violinist.C.There will be other musicians to introduce.D.It’S rather late toask Dantomake the introductionnow.8、A.She doesn’t have much trouble.B.She understood the reading last night.C.She understands very little.D.She hasn’tbe en doing much of the reading.9、A.The man has been complaining too much.B.The man’stoothache will goaway by itself.C.The man should have seen the dentist earlier.D.The man should confirm his appointment with the dentist.10、 Conversation One.听材料，回答下列问题。