篇一：实验四--同步机构
实验四 同步机构
一. 实验内容
模拟实现用同步机构避免并发进程执行时可能出现的与时间有关的错误。
二. 实验目的
进程是程序在一个数据集合上运行的过程，进程是并发执行的，也即系统中的多个进程轮流地占用处理器运行。
我们把若干个进程都能进行访问和修改的那些变量称为公共变量。由于进程是并发执行的，所以，如果对进程访问公共变量不加限制，那么就会产生“与时间有关”的错误，即进程执行后，所得到的结果与访问公共变量的时间有关。为了防止这类错误，系统必须要用同步机构来控制进程对公共变量的访问。一般说，同步机构是由若干条原语——同步原语——所组成。本实验要求学生模拟PV操作同步机构的实现，模拟进程的并发执行，了解进程并发执行时同步机构的作用。
三. 实验题目
模拟PV操作同步机构，且用PV操作解决生产者——消费者的问题。
四. 实验步骤
（1） 程序中使用的数据结构及符号说明
struct PCB //进程控制块
{
char p_name[23];
int m;// 0:运行,1:就绪,2:等待,3:完成;
int waitreason;//0:信号S1,1:信号S2;
int interuptpoint; //设置断点
};
const int num=5;
const int sales=10;
struct PCB; //进程控制块
void ce();
void p(int & s,int p,PCB *d); //P操作
void v(int & s,int p,PCB *d); //V操作
（2） 流程图
程序总体结构框图：
初始化：
初始化信号量S1，S2（S1=10,S2=0），对生产者、消费者进程的PCB初始化。
初始化流程图：
运行部分框图：
（3） 源代码（附注释）
//#include "stdafx.h"
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
const int num=5;
const int sales=10;
struct PCB; //进程控制块
void ce();
void p(int & s,int p,PCB *d); //P操作
void v(int & s,int p,PCB *d); //V操作
/*int _tmain(int argc, _TCHAR* argv[])
{
return 0;
}*/
struct PCB //进程控制块
{
char p_name[23];
int m;// 0:运行,1:就绪,2:等待,3:完成;
int waitreason;//0:信号S1,1:信号S2;
int interuptpoint; //设置断点
};
int produce(int &C,int c)//生产产品c
{
C=c;
return C;
}
int s1,s2,pa[num],sa[num],pc;
PCB producer,customer,*currp;
void initial() //初始化程序
{
strcpy_s(producer.p_name,"producer");
producer.m=1;//初始化生产者为就绪状态
producer.interuptpoint=0;
strcpy_s(customer.p_name,"customer");
customer.m=1; //初始化消费者为就绪状态
customer.interuptpoint=0;
currp=&producer;
s1=10;
s2=0;
for(int i=0;i<num-1;i++)
{
pa[i]=i;
sa[i]=pa[i];
}
pc=0;
}
void cpuwork()
{
currp->interuptpoint=pc; //令当前执行指令送到断点中
int n;
while(producer.m==1||customer.m==1)//判断当前执行是生产者，还是消费者
{
cout<<"选择生产者进程或消费者进程（0表示生产者，1表示消费者）：";cin>>n;
if(n==0)//0为表示生产者
{
if(producer.m==1)
currp=&producer;
else//否则消费者为就绪状态，执行消费者进程
{
cout<<"进程producer被挂起，无法执行，执行进程customer"<<endl; currp=&customer;
}
} else
if(n==1)//1为表示消费者
if(customer.m==1)
currp=&customer;
else//否则生产者为就绪状态，执行消费者进程
{
cout<<"进程customer被挂起，无法执行，执行进程producer"<<endl;currp=&producer;
}
currp->m=0; //令当前进程处于执行状态
pc=currp->interuptpoint;
ce();//执行
currp->interuptpoint=pc;
}
}
void ce()
{
int i,j,q,pt,xx,ss,nq,shangpin[sales],xiaofei[sales];
int C;
char w; xx=0;
ss=0;
nq=0
i=pc
if(strcmp(currp->p_name,"producer")==0)//pa[i]存放生产者程序中的一条模拟指令执行的入口地址
{
j=pa[i];
q=0;
}
else //sa[i]存放消费者程序中的一条模拟指令执行的入口地址
{
j=sa[i];
q=1;
}
pc=i+1;
switch(j)//j表示当前程序中的一条模拟指令执行的入口地址
{
case 0:
if(q==0)//输入一个字符放入中
{
cout<<"请生产一件产品（即输入一个数字）：";
cin>>pt;
produce(C,pt);
//pp=pt;
currp->m=1;
cout<<"产品已经生产";
}
else //执行消费者的P操作
{
nq=2;
p(s2,nq,currp);
}
break;
case 1:
if(q==0)//执行生产者的P操作
{
nq=1;
p(s1,nq,currp);
}
else//执行消费者的取商品操作，X:B[out];out:=(out+1)mod 10
{
cout<<"取一个产品";
xiaofei[xx]=shangpin[ss];
xx=(xx+1)%sales;
currp->m=1;
}
break;
篇二：必修四第四模块同步练习
Reading and Vocabulary
请根据首字母或汉语提示完成单词。
1. According to the rules of the work you should prefer quality to q_____.
2. Surgeons have made a great b______ in the kidney transplantation.
3. The new city, Brasilia, r______ Rio de Janeiro as the capital of Brazil in 1960.
4. Last year my brother g______ from Peking University and found a job there.
5. Some scientists like to e______ with small white mice.
6. Would you mind if I asked you a ______(个人) question?
7. The plastic surgeon ______ (诊断) my illness as a rare bone disease.
8. The two girls, who were twins, were the ______ (受害者) of a road accident.
9. The farmers are very pleased with the government’s ______ (农业的) policy.
10. The _____ (最初的) owner of the house was the Duke of Wellington.
请根据提示完成句子。
21. 他希望靠卖饮料来谋生。He hoped to _____ _____ _____ _____ _____ drinks.
22. 由于交通阻塞，他开会迟到了。He was late for the meeting _____ _____ _____ ______ a traffic jam.
23. 他执政后，为人民做了大量的工作。After he _____ _____ _____, he did a lot of work for the people.
24. 树上的鸟儿朝四面八方飞去。The birds in the trees flew _____ _____ _____.
25. 教授正在实验室做实验。The professor _____ ______ ______ ______ experiment in the lab.
26.去年那座楼房被改建成了学校。（convert） _______________________________
27. 当你读完这本书时，请放回原处。(replace )___________________________________
28. 她用教书挣的钱资助丈夫出国留学。(support)____________________________________
29. 去年他们从国外引进了一些先进的设备。（bring in）______________________________________
30. 这支鸟很幸运没有被抓住。（escape）______________________________
31. Hitler _______ in Germany in the 1930s,when he caused great sufferings to the world.
A. came to power B. came in power C. took power D. got power
32. An expert was _____ to give a speech on how to learn English well.
A. brought inB. brought on C. brought outD. brought up
33. — How are you getting on with your research?
— Very smoothly. I am going to _______.
A. break through itB. be broken through C. make a breakthrough D. break it through
34. As is well known ____ all, Yuan Longping is known ___ his rice. A. to; for B. to; as C. as; for D. for; as
35. My friend Martin was very sick with a strange fever; ____, he could neither eat nor sleep.
A. as a resultB. after allC. any wayD. otherwise
36. His great discover _____ his determination and devotion to science. A. led in B. led to C. resulted fromD. resulted in
37. The price of petrol has been ______ 20 percent since the beginning of this year.
A. increased to B. risen by C. increased by D. risen to
38. As a result of destroying the forests, a large ______ of desert _____ covered the land. (上海2001)
A. number, hasB. quantity; hasC. number, haveD. quantity; have
39. The old woman was diagnosed ______ lung cancer by the doctor and her life couldn’t last long.
A. of B. on C. with D. by
40. Mr Green, who is a member of Labor Party, has _____ Mr Brown as President.
A. taken placeB. taken the placeC. in place ofD. replaced
Grammar
1. The hero’s story ____ differently in the newspapers.A. was reported B. was reporting C. reports D. reported
2. A new cinema____ here. They hope to finish it next month.A. will be builtB. is built C. has been built D. is being built
3. John as well as the other children who _____ no parents ______ good care of in the village.
A. have; is being taken B. have; has taken C. has; is taken D. has; have been taken
4. ― Why did you leave that position?
―I _____ a better position at IBM. A. offerB. offeredC. am offeredD. was offered
5. I need one more stamp before my collection____.A. has completedB. completesC. has been completedD. is completed
6. — George and Lucy got married last week. Did you go to their wedding? A. was not invited B. have not been invited — No. I ____. Did they have a big wedding? C. hadn’t been invited D. didn’t invite
7. The mayor of Beijing says that all construction work for the Beijing Olympics ____ by 2006.
A. has been completed B. has completedC. will have been completed D. will have completed
8. The number of deaths from heart disease will be reduced greatly if people ____ to ear more fruit and vitamins.
A. persuadeB. will persuadeC. be persuadeD. are persuaded
9. Large quantities of cotton ______ shipped all over the world already while a large quantity of bamboo baskets ______ going to be exported to some western countries.A. have been; is B. has been; are C. have been; are D. has been; is
10. — Have you moved into the new house?
— Not yet. The rooms ______.A. are being paintedB. are painting C. are painted D. are being painting
11. The house ______ in the earthquake last year ______. A. destroyed; was belonged to me B. destroyed; belonged to me C. was destroyed; belonged to mine D. was destroyed; belonged to me
12. — _____ the sports meet might be put off.
— Yes, it all depends on the weather.A. I’ve been toldB. I’ve toldC. I’m toldD. I told
13. On her birthday, the girl is looking forward ____ a gift. A. to be given B. to being given C. to giveD. to giving Everyday English 从方框中选择适当的句子，完成对话（其中两项为多余）。
B: Hello. Zhao Guang. Nice to meet you, too. Do you know who will give us a report?
A: It is the great expert on hybrid rice — Yuan Longping.
B: ____2___? I’m lucky to have a chance to listen to his speech.
A: ____3___. It is Yuan Longping who’
s made a breakthrough on the hybrid rice.
B: That’s right. Yuan developed a new way to make the rice product increased by 45 percent. people have enough food to eat.
A: ___5____.
B: Exactly. Oh, time is up. Let’s enter the hall.
A: All right. Let’s go.
Cultural Corner
2. A new type of rocket _____ under the sea by a submarine.
3. We'll have tea in the garden _______ in the house.
4. China was ______ with Japan for eight years
5. She ______ a stamp to the envelope and mailed it.
6. A bomb ______ in the building and caused a big fire.
7. Rockets were probably invented ______ about 2,000 years ago.
8. The bird that I have fed for half a year _____ the cage the other day.
9. We ______ the candle and the candle made the room bright.
10. This is the village where the hero was born and ______.
参考答案
Reading and Vocabulary:
1. quantity 2. breakthrough3. replaced4. graduated5. experiment6. personal
7. diagnosed8. victims 9. agricultural 10. original
11. across 改为cross 12. from改为by13. Whom改为By whom或spoken后加by
14. 去掉been 15. out后加of或out改为from 16. result 后加of 17. by 改为to
18. was后加being 19. is sold改为sells20. publish改为be published
21. earn / make his living by selling
22. as a result of
23. came to power
24. in all directions / in every direction
25. is carrying out an
26. That building was converted into a school last year.
27. When you have finished reading the book, please replace it.
28. She supports her husband to study abroad by teaching.
29. They brought in some advanced equipment from abroad last year.
30. The bird was lucky and escaped being caught.
31-35 AACAA 36-40 CCBCD
Grammar:
1-5 ADADD 6-10 DCDBA11-13 BAA
Everyday English: 1-5 DBCAF
Cultural Corner:
1. is used to 2. was sent up 3. instead of 4. at war 5. attached 6. exploded 7. by accident
8. escaped from 9. lit 10. brought up
篇三：小学人教课标版四年级下册同步作文全集
小学人教课标版四年级下册同步作文
第一单元作文（写校园的景色）
一、习作内容：
我们都爱自己的校园，它也许像一座美丽的花园，绿草如茵，花团锦簇；它也许仅有平房，几棵老树，一个小操场。不管怎样，在可爱的校园里，我们都度过了许多快乐的日子。让我们到校园里走一走，看一看，选一处景物，仔细观察一下，把观察到的按一定的顺序写下来。注意把内容写具体，语句写通顺。如果不想写校园里的景物，也可以写别处的景物，或者写校园里发生的事。
二、习作分析：
1习作内容范围很宽泛，只要和景物有关的都可以写。 2观察有特点的景物，按照一定的顺序来写。
3在小组内交流自己的想法，然后把自己想好的内容写下来。 4写好后，和同学相互交流习作，互改互评。
佳作欣赏一：校园之春
绵绵的春雨，暖暖的春风，春的脚步已踏进我们的校园。神奇魔棒下的校园，开始流露出无限的蓬勃生机。
清晨，透过朦胧的晨雾，隐隐约约能看见几个身影陆续走进教学楼。“一年之计在于春，一日之计在于晨。”同学们深知要抓住学习的大好机会，不一会儿，琅琅的读书声响彻校园，真是“风声雨声声声入耳”。
“吹面不寒杨柳风”，轻柔的风拂面而来，带来凉丝丝的气息。校园南门的竹林奏起了交响曲，“沙沙沙”，“沙沙沙”，好个热闹的“竹”林盛会，片片细叶轻歌曼舞，肩碰着肩，脚踏着脚，身着翡翠盛装。
牛毛般的细雨轻盈地飘落进花坛，娇艳的茶花伸伸懒腰，笑盈盈的，好像在问春雨：“你看我漂亮吗？”红瓣粉蕊，一团团，一簇簇，如点染了胭脂一般，红得耀眼，美得醉人。旁边，月季仰着粉嫩粉嫩的小脸，冲我们点头微笑，好像在说：“瞧啊，我要把校园装点得更美！”
几棵高大苍翠的水杉、雪松像勇敢的卫士，挺直身躯，一直保持充沛的精力，使娇嫩的花儿倍受呵护，用她最纯真可爱的笑脸装点校园，使同学们在它挺拔的身躯下快乐地嬉戏玩耍。
朗朗的读书声，醉人的花香，精神饱满的花草树，组成了一幅优美迷人的校园春景。
佳作欣赏二：美丽的校园
春姑娘跳着欢快的舞蹈向校园走来。
前些天，校园里的桃花开了，粉色的，白色的，淡黄色的，有的像翩翩起舞的少女；有的像害羞的小姑娘；有的像善良的小天使，只要你在桃花前深吸一口气，一定会闻到它那淡淡的花香。
当春天的校园下起蒙蒙细雨的时候，那一朵朵五颜六色的桃花便镶满了晶莹的露珠，从远处看，好像整个校园都变成了水晶般的世界，
晶莹剔透。雨一会就停了，湿润的空气夹杂着桃花的芬芳扑面而来，让你在校园里，流连忘返。
柳树也抽出了新枝，长出了嫩叶。刚冒出的嫩叶，一片片抱在一起，只几天功夫，就一片片分开了，变得又多又密，十分美丽，远远望去，好像一把巨大的遮阳伞。鸟儿在枝头唱着欢快的歌，告诉我们：“春天来了，春天来了。”
我爱美丽的春天，更爱这春天的校园。
点评：把春天的校园写得很美 。感觉细腻，想象丰富，善于用形象的比喻来描绘事物，给人以生动的印象。
佳作欣赏三：春姑娘到校园
春姑娘迈着轻盈的步子悄悄地来到校园，把年迈的冬婆婆送走了，给校园增添了无限生机。
一进校门，一阵清香迎面扑来。原来是大花坛里的月季让我们慢慢陶醉。走近些，它露出了粉红粉红的小脸儿，再往旁边看，几棵亭亭玉立的不知名的黄色的小花争奇斗艳，似乎在比谁更漂亮。大花坛的边上，一圈锯齿形的小树把花坛围了个水泄不通，像护卫一样保护着花。花坛中央，“野火烧不尽，春风吹又生”的小草迫不及待的破土而出，把荒野涂成了绿色。
我向前走去，下了几步台阶就来到篮球场。升旗台旁，几棵威武的柏树端正地站在那里，很有气势。仔细一看，它的叶子像毛毛虫，枝上带着细细的刺。一阵风吹过它们就翩翩起舞，抖抖身子，像在跳迪斯科。
站在升旗台上往下望，运动场上有一棵参天大树，可能年龄比我大得多吧！春姑娘拂袖而过，把树爷爷的衣服变成了翠绿色，虽说树爷爷身子凹凸不平，但是还有可爱的小鸟在上面建巢。天天给年迈的树爷爷唱歌，连春姑娘都看笑了！
自从春姑娘来了以后，校园里焕然一新。春姑娘，你可真会变魔术啊！
佳作欣赏四：校园的春天
春天到了，校园里会变成什么样呢？让我们赶快去看看吧！ 操场两边的大树悄悄地发出了一个个绿油油的小叶苗，最引人注目的还是那棵大杨树了，它是校园里最高大的树了！每到春天它长完叶子时，树枝上就挂满了一簇簇像棉花似的白絮絮，好玩极了！有的同学把白絮絮集到了一个盒子里，可能是想做东西吧。
树上的小鸟也在空中飞来飞去，叽叽喳喳的好像在告诉人们“春天到了，春天到了！”树根旁边睡了一冬天的小草钻出地面，正在争先恐后地生长着，似乎是怕自己得不了第一吧！花坛里的花经过细雨的滋润长出了嫩绿的叶子，散发出了淡淡的香气。这些花草树木从远处看就像一张五颜六色的大地毯，为校园增添了点点新绿。
在大树前面是丰富多彩的奥运墙，上面有晶晶，贝贝，迎迎，妮妮和欢欢五个小福娃的简介和图，其中我最喜欢小羚羊迎迎了!因为它代表着美好的祝福。奥运墙上还介绍了一些运动员呢！
校园的春天真美丽啊！那些花草树木为校园增添了勃勃生机，只要细心观察春天的校园一定会有有趣的发现。让我们来迎接美丽的春
天吧！
第二单元作文（写自己成长过程中的心里话）
一、习作内容：
在自己成长的过程中，你是不是有很多心里话要说，却没有机会说出来？这一次，就让我们在自己的习作中一吐为快吧！例如，对老师说，为了我们的成长，您操碎了心；对妈妈说每位已经长大了，别在把我当小孩子看；对邻居叔叔说，谢谢您多年来对我们家真诚的帮助；对小伙伴说，我们不要再互相起外号了，这样不文明??总之，敞开心扉，把自己心里想说的话，在习作里向对方说一说。说心里话，就一定要真实，要说出内心的想法。写完后可以读给对方听，再根据别人意见改一改。
现在，清楚了吧，本次习作的内容是──写自己成长过程中的心里话。
二、习作分析：
1习作的题目自拟，选择的人称可以是第一人称，也可以是第二人称。可以用书信、书信等形式。理解心里话的意思。
2想好写哪些方面的心里话？为什么会这样想？
3小组内相互交流，互相评议。是否真实地表达了自己的内心感受。
佳作欣赏一： 向爸爸妈妈说说心里话
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