It’s directly showed in this chart that the trend of the population above sixty goes up. So does the proportion of the old in total population. What’s worse, there has no evidence to show that this tendency will stop in the future. It shows one of the pressing social problems deserving our attention as well as consideration in China society
China faces a rapidly aging population, and the country’s one-child policy means its household-centered elderly care will be increasingly difficult to maintain in the future. Every child may take care of four old men. If we let this tough problem go, we will meet an unparalleled serious short of not only in labor force but also in our army. It will be a huge burden for government to pay for such a giant amount of pension. So does the health care system.
What can we do to tackle with this troublesome occurrence?
Initially, a package of regulations and laws about relaying the age of retiring will come on. The media spare every effort to motivate the citizen work more years for not only every single person but also the countryas a whole. What’s more, the reformation in both health care and social security system will carry on. We should have confidence to the life quality of our retirement time. An increasing number of
corporationsbelieve that the old will become a strong force in the future consume market. It will be a new strategy to impel ole people spending money and develop the economy. It will stimulate the service system of Most of people choose living at home. It’s a responsibility to feed back parents when they turn old. Many young people are willing to live with their parents although they have married. Not only can we communicate with our parents, but also they can help us do some housework.
But many people are ready to living at nursing home. Their children are busy with working at weekdays. When something happened suddenly, they can’t ask for help timely. But nursing home has many problems too, such as elder maltreatment…
No matter which way you choose, please remember to talk with old people and make them happy. It’s them makes you what you are today. They give their love all to us, and we must take good care of them.
It’will stimulate the development of public service system and service industry.
t's directly showed in this chart that the trend of the population above sixty goes up. So does the proportion of the old in total population. What's worse, there is no evidence showing that this tendency will stop in the future. It shows one of the pressing social problems deserving our attention as well as consideration in China society
China faces a rapidly aging population, and the country's one-child policy means its household-centered elderly care will be increasingly difficult to maintain in the future. Every child may take care of four old men. If we let this
tough problem go, we will meet an unparalleled serious short of not only in labor force but also in our army. It will be a huge burden for government to pay for such a giant amount of pension. So does the health care system.
What can we do to tackle with this troublesome occurrence?
Initially, a package of regulations and laws about relaying the age of retiring will come on. The media spare every effort to motivate the citizen work more years for not only every single person but also the country as a whole. What's more, the reformation in both health care and social security system will carry on.We should have confidence to the life quality of our retirement time. An increasing number of corporations believe that the old will become a strong force in the future consume market. It will be a new strategy to impel ole people spending money and develop the economy. Many people are ready to living at nursing home. Their children are busy with working at weekdays. When something happened suddenly, they can't ask for help timely. But nursing home has many problems too, such as elder maltreatment-It' will stimulate the development of public service system and service industry.
No matter which measure we will take, please remember to talk with old people and make them happy. It's our obligation to take good care of them. But for their effort,I won't be what I am today. They give their love all to us, and we must take good care of them.
操作系统第四版-课后习题答案
第一章 作者：佚名来源：网络 1、有一台计算机，具有IMB 内存，操作系统占用200KB ，每个用户进程各占200KB 。如果用户进程等待I/O 的时间为80 % ，若增加1MB 内存，则CPU 的利用率提高多少？ 答：设每个进程等待I/O 的百分比为P ，则n 个进程同时等待刀O 的概率是Pn ，当n 个进程同时等待I/O 期间CPU 是空闲的，故CPU 的利用率为1-Pn。由题意可知，除去操作系统，内存还能容纳4 个用户进程，由于每个用户进程等待I/O的时间为80 % , 故： CPU利用率＝l-（80%)4 = 0.59 若再增加1MB 内存，系统中可同时运行9 个用户进程，此时：cPu 利用率＝l-（1-80%)9 = 0.87 故增加IMB 内存使CPU 的利用率提高了47 % : 87 ％/59 ％=147 % 147 ％-100 % = 47 % 2 一个计算机系统，有一台输入机和一台打印机，现有两道程序投入运行，且程序A 先开始做，程序B 后开始运行。程序A 的运行轨迹为：计算50ms 、打印100ms 、再计算50ms 、打印100ms ，结束。程序B 的运行轨迹为：计算50ms 、输入80ms 、再计算100ms ，结束。试说明（1 ）两道程序运行时，CPU有无空闲等待？若有，在哪段时间内等待？为什么会等待？( 2 ）程序A 、B 有无等待CPU 的情况？若有，指出发生等待的时刻。 答：画出两道程序并发执行图如下： （1）两道程序运行期间，CPU存在空闲等待，时间为100 至150ms 之间（见图中有色部分） （2）程序A 无等待现象，但程序B 有等待。程序B 有等待时间段为180rns 至200ms 间（见图中有色部分） 3 设有三道程序，按A 、B 、C优先次序运行，其内部计算和UO操作时间由图给出。
1、“整体对换从逻辑上也扩充了内存，因此也实现了虚拟存储器的功能”这种说法是否正确请说明理由。 答：上述说明法是错误的。整体对换将内存中暂时不用的某个程序及其数据换出至外存，腾出足够的内存空间以装入在外存中的、具备运行条件的进程所对应的程序和数据。虚拟存储器是指仅把作业的一部分装入内存便可运行作业的存储器系统，是指具有请求调入功能和置换功能，能从逻辑上对内存容量进行扩充的一种存储器系统，它的实现必须建立在离散分配的基础上。虽然整体对换和虚拟存储器均能从逻辑上扩充内存空间，但整体对换不具备离散性。实际上，在具有整体对换功能的系统中，进程的大小仍受到实际内存容量的限制。 2、某系统采用页式存储管理策略，拥有逻辑空间32页，每页为2KB，拥有物理空间1MB。 1）写出逻辑地址的格式。 2）若不考虑访问权限等，进程的页表有多少项每项至少有多少位 3）如果物理空间减少一半，页表结构应相应作怎样的改变 答：1）该系统拥有逻辑空间32页，故逻辑地址中页号必须用5位来描述，而每页为2KB，因此，页内地址必须用11位来描述。这样，可得到它的逻辑地址格式如下： 2）每个进程最多有32个页面，因此，进程的页表项最多为32项；若不考虑访问权限等，则页表项中只需给出页所对应的物理块号。1MB的物理空间可分成29个内存块，故每个页表项至少有9位。 3）如果物理空间减少一半，则页表中项表项数仍不变，但每项的长度可减少1位。 3、已知某系统页面长4KB，每个页表项为4B，采用多层分页策略映射64位的用户地址空 间。若限定最高层页表只占1页，则它可采用几层分页策略 答：方法一：由题意可知，该系统的用户地址空间为264B，而页的大小为4KB，故作业最多可有264/212（即252）个页，其页表的大小则为252*4（即254）B。因此，又可将页表分成242个页表页，并为它建立两级页表，两级页表的大小为244B。依次类推，可知道它的3、4、5、6级页表的长度分别是234B、224B、214B、24B，故必须采取6层分页策略。 方法二：页面大小为4KB=212B，页表项4B=22B，因此一个页面可以存放212/22=210个面表项，因此分层数=INT[64/10]=6层 4、对于表所示的段表，请将逻辑地址（0，137）、（1，4000）、（2，3600）、（5，230）转换 成物理地址。 答：[0,137]：50KB+137=51337； [1，4000]：段内地址越界；
一、 HanselandGretel______(live)nearaforestwithhisfatherandstepmother.Oneyear,theweather______(be)sodry thatnofood_____(grow).Thewifetoldherhusbandthatunlesshe________(leave)hischildren______(die)inthe forest,thewholefamilywoulddie.Gretel_________(hear)thattheirstepmotherplanned________(kill)herandh erbrother.ButHanselhadaplan________(save)himselfandhissister.Hewenttogetsomewhitestonesbeforehew enttobedthatnight.Thenextday,thewife_________(send)thechildrentotheforest.Hansel___________(drop)t https://www.doczj.com/doc/d011228341.html,terthatnight,they________(see)thestonesbecauseoftheshiningmoon.Thestones__ ace)forthisistheHimalayas.TheHimalayasrunalongthe______________(southwest)partofChina.Ofallthem ountains,Qomolangma________(rise)thehighestandis____________(famous).Itis8,844.43metershighands oisverydangerous________(climb).Thickcloudscoverthetopandsnow__________(fall)veryhard.Evenmore serious_______(difficulty)includefreezingweatherconditionsandheavystorms.Itisalsoveryhard_____(take) inairasyougetnearthetop. Thefirstpeople_____(reach)thetopwereTenzingNorgayandEdmundHillaryonMay29,1953.ThefirstChi neseteam__(do)soinI960,whilethefirstwoman_____(succeed)wasJunkoTabeifromJapanin1975. Whydosomanyclimbersrisktheir_____(life)?Oneofthemain_______(reason)isbecausepeoplewant______(c hallenge)themselvesinthefaceofdifficulties. Thespiritoftheseclimbers_____(show)usthatweshouldnevergiveup____(try)toachieveourdreams.Itals
Folk Music 中国民乐 Beijing Opera 京剧 Local Operas 地方戏 Outline ?China, a nation of long history with profound culture, ?inherited and developed a great variety of traditional art forms which suit both refined and popular tastes 雅俗共赏. ?From the melodious and pleasant folk music to the elaborate and touching local dramas, ?from the simple but elegant inkwash painting(水墨画) to the flexible and powerful calligraphy, ?one can always discern the light of sparkling wisdom. ?Traditional Chinese arts have tremendously impressed the world. ?Chinese folk music, with strong nationalistic features, is a treasure of Chinese culture. ?As early as the primitive times, Chinese people began to use musical instruments, ?which evolved today into four main types categorized by the way they are played 吹拉弹打.materials they are made of （丝竹管弦）. stringed instrument 丝：弦乐器 wind instrument 竹：管乐器 ?吹：The first type is wind instrument 管乐器, as show in xiao （a vertical bamboo flute ）箫，flute 笛子, suona horn 唢呐, etc. ?拉：The second type is string instrument 弦乐器, represented by urheen 二胡, jinghu 京胡（a two-string musical instrument similar to urheen ）, banhu fiddle 板胡, etc.
操作系统期末考试（一） 一、单项选择题（在每小题的四个备选答案中，只有一个是正确的，将其号码写在题干的括号中。每小题2分，共20分） 1、文件系统的主要组成部分是（） A、文件控制块及文件 B、I/O文件及块设备文件 C、系统文件及用户文件 D、文件及管理文件的软件 2、实现进程互斥可采用的方法（） A、中断 B、查询 C、开锁和关锁 D、按键处理 3、某页式管理系统中，地址寄存器的低9位表示页内地址，则页面大小为（） A、1024字节 B、512字节 C、1024K D、512K 4、串联文件适合于（）存取 A、直接 B、顺序 C、索引 D、随机 5、进程的同步与互斥是由于程序的（）引起的 A、顺序执行 B、长短不同 C、信号量 D、并发执行 6、信号量的值（） A、总是为正 B、总是为负 C、总是为0 D、可以为负整数 7、多道程序的实质是（） A、程序的顺序执行 B、程序的并发执行 C、多个处理机同时执行 D、用户程序和系统程序交叉执行 8、虚拟存储器最基本的特征是（） A、从逻辑上扩充内存容量 B、提高内存利用率 C、驻留性 D、固定性 9、飞机定票系统是一个（） A、实时系统 B、批处理系统 C、通用系统 D、分时系统 10、操作系统中，被调度和分派资源的基本单位，并可独立执行的实体是（） A、线程 B、程序 C、进程 D、指令 二、名词解释（每小题3分，共15分） 1.死锁: 2.原子操作: 3.临界区: 4.虚拟存储器: 5.文件系统: 三、判断改错题（判断正误，并改正错误，每小题2分，共20分） 1、通道是通过通道程序来对I/O设备进行控制的。（） 2、请求页式管理系统中，既可以减少外零头，又可以减少内零头。（） 3、操作系统中系统调用越多，系统功能就越强，用户使用越复杂。（） 4、一个进程可以挂起自已，也可以激活自已。（） 5、虚拟存储器的最大容量是由磁盘空间决定的。（） 6、单级文件目录可以解决文件的重名问题。（） 7、进程调度只有一种方式：剥夺方式。（） 8、程序的顺度执行具有顺序性，封闭性和不可再现性。（） 9、并行是指两个或多个事件在同一时间间隔内发生，而并发性是指两个或多个事件在 同一时刻发生。（） 10、进程控制一般都由操作系统内核来实现。（） 四、简答题（每小题5分，共25分） 1、简述死锁产生的原因及必要条件。 2、什么是多道程序技术，它带来了什么好处？ 3、有结构文件可分为哪几类，其特点是什么？ 4、分时系统的基本特征是什么？ 5、分页系统与分段系统的区别主要在于哪些方面？