GDB用法小结

第一篇：GDB用法小结

GDB用法小结

1.gdb exe 使得exe程序运行在debug环境下 2.break functiona 在functiona函数处设置端点

3.run 让程序从main入口执行到断点functiona 4.n next,单步执行，相当于VC中的调试命令step over 5.s step into,进入子函数，察看子函数的执行情况 6.bt backtrace查看堆栈的情况 7.p variant print出变量variant的值 8.l list命令，查看当前的行的上下文，默认显示10行 9.p variant=correct value 如果发现此时的variant的值不正确，我们可以给variant设置一个正确的值(correct value)然后，用第10项中的命令继续执行 10.c continue 继续执行，可以是经过按照更改后的值继续执行。相当于VC中的F5 11.quit or Ctrl+C 退出gdb

在gdb的命令行下，可以通过file exeprogram 载入要debug的文件 gdb-silent 表示不提示GDB的版权信息 or gdb-q(quiet)gdb-h 显示gdb的帮助 About Help gdb>help

apropos args //查找所有的GDB命令以及它的文档中包含args的表达式 complete i //列出所有以i开头的gdb命令

针对某一个命令的帮助是help command，例如help info 显示info的用法，info 可以查看args，breakpoints,stack......show命令只要是显示gdb的信息，如show version break break function 在某一个函数的地方设置端点

break linenum 在确定的某一行的地方设置断点

break +offset-offset

break *address在某一个地址设置断点 14 watch watch expr 查看某一个表达式

rwatch expr 查看某一个表达式，并在读入该表达式的时候，设置断点

查看源代码

list lineNum 在lineNum的前后源代码显示出来

list + 列出当前行的后面代码行

list=>;上次显示程序代码的前面的十行。

断点的设定与清除

1.设定断点(指令为 break，可简写为(b)，格式计有：

(gdb)break filename.c:30 =>;在 filename.c 的第三十行处停止执行。

(gdb)break function =>;在进入 function 时中断程序的执行。

(gdb)break filename.c:function =>;在程序代码档 filename.c 中的函数 function 处设定断点。

(gdb)break =>;在下一个将被执行的命令设定断点。

(gdb)break...if cond =>;只有当 cond 成立的时候才中断。cond 须以 C 语言的语法写成。

2.显示各个断点的信息。

(gdb)info break

3.清除断点(命令为 clear)，格式同 break。例如 :(gdb)clear filename.c:30

4.清除断点，NUM 是在 info break 显示出来的断点编号。

(gdb)delete NUM 全速及逐步执行程序

1.从程序开头全速执行程序，直到遇到断点或是程序执行完毕为止。

(gdb)run

2.在程序被中断后，全速执行程序到下一个断点或是程序结束为止(continue 指令可简写为 c)。

(gdb)continue

3.执行一行程序.若呼叫函数, 则将该包含该函数程序代码视为一行程序(next 指令可简写为 n)。

(gdb)next

4.执行一行程序.若呼叫函数, 则进入函数逐行执行(step 指令可简写为 s)。

(gdb)step

5.执行一行程序，若此时程序是在 for/while/do loop 循环的最后一行，则一直执行到循环结束后的第一行程序后停止(until 指令可简写为 u)。

(gdb)until

6.执行现行程序到回到上一层程序为止。

(gdb)finish 检视及更改变量值

1.print 叙述，显示该叙述执行的结果(print 指令可简写为 p)。如

(gdb)print a =>;显示 a 变量的内容.(gdb)print sizeof(a)=>;显示 a 变量的长度.2.display 叙述，在每个断点或是每执行一步时显示该叙述值。如

(gdb)display a

3.更改变量值：

(gdb)print(a=10)=>;将变量 a 的值设定为 10.检视程序执行状态

1.查看程序执行到此时，是经过哪些函数呼叫的程序(backtrace 指令可简写为 bt)，也就是查看函数呼叫堆栈。(gdb)backtrace 读取 Core 文件信息

1.读入 PROGRAM 及 PROGRAM.CORE 档，可检视 Core Dump 时程序变量值及程序流程状态。gdb PROGRAM core

说明：'core' 档案是由 PROGRAM 档执行后，遇到 Core Dump 时产生的 Core 檔檔名。如果你还需要该 Core 档，我们建议你将该档案档名更改为 PROGRAM.core。在输入上述命令后，你可以用 GDB 提供的检视变量值以及检视程序执行状态来读取程序 Core Dump 时的状态。

第二篇：it用法小结

小结(2008-12-08 15:57:31)

标签：教育

It用法小结

it在英语语法中属人称代词，意思是“它”，用来指人以外的一切生物和事物。它的用法不仅不简单，而且很复杂。

一、用于指人以外的一切生物、无生命的东西和事情。

一般指说话者心目中已经了解或所指的生物、无生命的东西或事情、没有性别的区分；可以是可数名词，也可以是不可数名词，在句子中既可做主语，也可以作宾语。

1．指动物和植物。如：

—Oh，that's Lucy's hat．噢，那是露茜的帽子。

—It looks like a cat！它看上去像只猫！

Where's tea grown？It's grown in the southeast of China．

什么地方种植茶？中国东南部种植茶。

2．指代一些无生命的东西。如：

Is it your watch？这是你的手表吗？

Look at the rain！It's heavy，isn't it？看这雨！雨很大，对吗？

3．代替上文提到过的整个事情。如：

Well，you mustn't play on the road．It's dangerous．哦，你不能在公路上玩。这太危险了！It was hard work，but they really enjoyed it．摘苹果是艰苦活，可他们都乐意去干（它）。

二、用于指代人。

1．指代说话者心目中不太清楚的那个人，常在打电话或敲门时用。如：

—Who was it？是谁（打来的电话）？

—Was it Susan？（打电话的）是苏珊吗？

—Yes，it was．是的，我是。（根据上下句，“it was”也可不译出来。）

再如：—Who is knocking at the door？谁在敲门？

—It's me．是我。

2．指说话者心目中的那个人。如：

—Is it your sister，Kate？（那旧照片上的 baby）是你姐姐凯特吧？

—No！不是。

—Is it your brother？是你哥哥吧？

—No！不是。

—I know—it's you！我知道了，（那）是你。

3．指代性别不详的婴幼儿或在不计较性别时，也可用it来指人。如

The child smiled when it saw its mother．这小孩一见到母亲就笑了。

I don't know who it is．我不知道他是谁。

注意：看到这样的句子（或听到这样的话）时，要想一想，不要一看到it就把它译成“它”。）

4．在回答用指示代词表示人的特殊问句时，常用it指人。如：

—Who's that？那人是谁？

—Is it Kate？是凯特吗？

—Yes，I think you're right．It's Kate．是的，我想你说对了，是凯特。

三、用于指时间、距离和自然现象等。

1．表示时间。如：

—What time is it？几点钟？

—It's ten．十点钟。

It's summer in Australia now．现在澳大利亚是夏天。

特别注意it用于表示时间时还常见于以下两个句型中：

（1）It's time（for sb．）to do sth．／It's time for sth．译为“是（某人）该干„„的时间了”、“到„„的时候了”。如：

It's time for supper／to have supper．是吃晚饭的时候了。

I think it's time for us to start the lesson now．我想现在是我们开始上课的时候了。

（2）It is ／has been ＋时间段＋since ＋一般过去时。译为“自从„„以来已过了„„（时间）”。此结构可以与另一种句型进行同义句转换。如：

It has been two weeks since we met last．＝ Two weeks has passed since we met last．自从我们上次相遇以来，两个星期过去了。

It's three years since he came here．＝It has been three years since he came here．＝He has been here for three years．他到这里已经三年了。

2．表示距离。如：

It's half an hour's walk from my home to the school．从我家到学校步行得花半小时时间。—Where's the farm，Li Lei？Is it far？李雷，农场在哪里？远吗？

—No，it's quite near．不，（距）离这很近。

3．表示自然现象。如：

Sometimes it snows and the land is all white．有时下雪，大地一片白。

It is very quiet here at the moment．眼下这儿很安静。

四、用作形式主语。

英语中常常见到某个句子以it开头，it与其后面的动词不定式短语、动名词短语、名词性从句等相呼应，以表达一个完整的意义。这是一种习惯表达法，这样的句式可避免句子显得头重脚轻。

1．It＋is／was＋形容词＋（for／of sb．）＋动词不定式短语。对于这个句型中究竟用 for还是用of，一般遵循这样的规则：如果形容词仅仅是描述事物的形容词，如：difficult，easy，hard，important，dangerous等用for；如果形容词是描述不定式行为者的性格、品质的，如：kind，good，nice，clever等则用of。如：

It is interesting to play with snow in winter．冬季里玩雪是很有趣的。

It's important for us to keep the water clean．保持水质清洁对我们来说是很重要的。It's very kind of you to say so．你这样说真是太好了。

注意：这一句式中的形容词位置也可换用名词；连系动词be也可换用其它连系动词，如feel等。如：

It's a good habit to get up early and go to bed early．早睡早起是好习惯。

It must be great fun to fly to the moon in a spaceship．乘宇宙飞船飞往月球一定很有趣。It feels strange to have a twin sister．有个孪生姐妹感觉很奇怪。

2．It ＋will be／is ／was ＋形容词＋动名词短语。如：

It's bad playing in the street．在街上玩是没好处的。

Is it any good trying again？再试一次有用吗？

3．It＋is／was＋形容词＋从句。如：

It is certain that he will come．他一定会来。

It's true that he may fall behind the other students．他真的可能落后于其他同学。

It is strange that he should say so．他居然这么说，真是奇怪。

4．It ＋is ／was ＋one's turn（duty，pleasure）＋to do sth．意为“该轮到某人做某事（做某事是某人的责任、愉悦的事）”。如：

It's your turn to be on duty tomorrow．明天轮到你值日了。

5．It takes（sb．）some time to do sth．意为“（某人）花„„时间做某事”。如

It took me a week to finish reading the book．我花了一周时间看完这本书。

6．It ＋cost／costs ＋sb．＋some money ＋to do sth．译为“某人花多少钱做某事”。如：It cost me 260 yuan to buy the new watch．我买这块新手表花了260元。

7．It seems ／seemed ＋从句。译为“看起来好像„„”，此结构可以转换成“seem ＋动词不定式”形式。如：

It seems that he is ill．＝He seems to be ill．看起来他好像病了。

[原题再现]

①________is a fact that English is being accepted as an international language.A.ThereB.ThisC.ThatD.It

② In fact________ is a hard job for the police to keep order in an important football match.A.thisB.thatC.thereD.it

答案: ① D ② D

五、用作形式宾语。

当句子的真正宾语是动词不定式、动名词或从句时，为避免句子头重脚轻，须将其放在宾语补足语之后，改用先行词it占据其原来的位置。it用作形式宾语的句型为：主语＋谓语＋it＋宾语补足语＋动词不定式／动名词／从句。该句型中宾语补足语可由形容词、名词等充当。如：

He found it not easy to learn a foreign language well．他发现学好一门外语是不容易的。We think it no good reading in bed．我们认为躺在床上看书无益处。

I think it necessary that we have the meeting．我认为开这个会是必要的。

[原题再现]

Don't ________that all those who get good grades in the entrance examination will prove to be most successful.A.take as grantedB.take this for granted

C.take that for grantedD.take it for granted

答案: D

六.构成强调句。

如：

It was in the street that I saw Li Ping this morning.今天早晨，就是在街上我看见李明。

[原题再现]

________was in 1979________I graduated from university.A.That;that B.It;that C.That;when D.It;when

答案: B

七.构成特殊句式。如：

It seems as if we should finish it tomorrow.【练习】

（1）There is a photo on the wall.____ the photo of Lei Feng.A.It B.Its C.It's D.He（高考，1980)

（2)Is＿necessary to tell his father everything?

A.it B.that C.what D.he(MET1987)

(3)Is＿possible to fly to the moon in a spaceship?

A.now B.man C.that D.it

(4)I consider____ my duty to help you．

A.it B.this C.that D.its

(5).It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.A.while B.that C.when D.as

答案：(1)C(2)A(3)D(4)A(5)B

(6)．I like ____ in the autumn when the weather is clear and bright.（2004全国I）

A.this B.that C.it D.one

(7).-Do you like ___ here?

-Oh，yes.The air，the weather，the way of life.Everything is so nice.（2004全国II）

A.this B.these C.that D.it

(8)．The Parkers bought a new house but ____ will need a lot of work before they can move in.A.they B.it C.one D.which

(9).I hate___ when people talk with their mouths full.A.it B.that C.these D.them

(10).Joan had often heard____ said that Marley had no money.A.it B.this C.that D.one

答案：C D B A A

八、it, one和that作替代词的用法及区别

it, one和that虽然都可以用来替代前面所提到的一个单数名词,以避免重复,但在具体用法上却有不同。简述如下:

1.it代替前面提到的同一事物,该事物既可以是可数名词也可以是不可数名词。

[原题再现]

The news that they failed their driving test discouraged him, ______?

A.did theyB.didn't theyC.did itD.didn't it

答案: D

2.one代替前面提到的同类事物中的一个。该事物只能是可数名词,前面可以有冠词,也可以被this、that或形容词修饰,其后也可以有定语。

[原题再现]

-Why don't we have a little break?

-Didn't we just have________?

A.it B.that C.one D.this

答案: C

3.that代替前面提到的同类事物中特指的一个。该事物既可以是可数名词也可以是不可数名

词,要有后置定语,但不可以有前置修饰语。

[原题再现]

Few pleasures can equal ________ of a cool drink on a hot day.A.someB.anyC.thatD.those

答案: C

高考“it”的用法英语题

历届高考英语单项选择题精选

（一）“it”的用法

1.Was it during the Second World War_____ he died?

A.thatB.while

C.in whichD.then(88)

2.Is ____ necessary to complete the design before National Day?

A.thisB.that

C.itD.he(89)

3.I don

t think ____ possible to master a foreign language without much memory work.A.thisB.that

C.itsD.it(91)

4.Does ______ matter if he can’t finish the job on time?

A.thisB.that

C.heD.it(91)

5.It was not _____ she took off her glasses _____ I realized she was a famous film star.A.when , thatB.until , that

C.until , thatD.when , then(92)

6.I was disappointed with the film.I had expected ______ to be much better.A.thatB.this

C.oneD.it(93)

7.It was not until 1920 ______ regular radio broadcasts began.A.whileB.which

C.thatD.since(94)

8.______is a fact that English is being accepted as an international language.A.ThereB.This

C.ThatD.It(95)

9.It was only when I reread this poems recently _____ I began to appreciate their beauty.A.untilB.that

C.thenD.so(97)

10.I hate _____ when people talk with their mouths full.A.itB.that

C.theseD.them(98)

11.It is the ability to do the job _____ matters not where you come from or what you are.A.oneB.that

C.whatD.it(2000)

KEYS:1-5 ACDDB6-10 DCDBA11 B ’

第三篇：with用法小结

with用法小结

一、with表拥有某物

Mary married a man with a lot of money.马莉嫁给了一个有着很多钱的男人。

I often dream of a big house with a nice garden.我经常梦想有一个带花园的大房子。

二、with表用某种工具或手段

I cut the apple with a sharp knife.我用一把锋利的刀削平果。

Tom drew the picture with a pencil.汤母用铅笔画画。

三、with表人与人之间的协同关系

make friends with sb

talk with sb

quarrel with sb与……吵架

fight with sb与……打架

play with sb

work with sb years since we worked with each other, and I have never quarreled with him.自从我们一起工作以来，我和汤姆已经是十年的朋友了，我们从没有吵过架。

四、with 表原因或理由.这种语义的with多半与表示情绪的词连用.John was in bed with high fever.约翰因发烧卧床。

He jumped up with joy.他因高兴跳起来。

Father is often excited with wine.父亲常因白酒变的兴奋。

五、with 表“带来”，或“带有,具有”，”在…身上，在…身边”之意（相当于having, carrying）

The girl with golden hair looks beautiful.那个金头发的女孩看起来漂亮。

The famous director will come to the meeting with the leading actor and actress.那个有名的导演将带着男女主角来到会场。

Do you have money with you.身上带着钱吗？

Take the umbrella with you in case it rains.随身带伞，以防下雨。

注意：with ,about ,和in均可表示特征和属性.With表示属于人和物的显著特点;about表示附属于人或物不可捉摸的的特点;in表示附属与人或物的内部固有特点.﹡His uncle is an old man with a red nose.它的叔叔是位红鼻子老人。

﹡There is a certain charm about that man.那个人有某种魅力。

﹡There is something strange in him.他身上有点奇怪的地方。

六、with表想法，信念，态度与…一致

I agree with you on how to deal with it.关于此事如何处理，我同意你的看法。

七、with表示让步,“虽有,尽管”

With all his money and fame, he is not happy.有着钱和名誉，他还是不快乐。

With good teachers and warmhearted classmates, the new comer feels lonely.虽有着好老师和热心的同学，这个新来的还是感觉孤独。

八、with表同时，或同一方向，“随着”

The temperature of cold-blooded animals change with the temperature of the surroundings.冷血动物的体温随着周围的环境的改变而变化。

The big ship is sailing with the wind.这个大船正随风向航行。

And with the last words, she turned away.随着最后一句话说完，他转身离开了。

九．With后加上一个名词（多为表情绪的词），表示“。。。地”等情态意义，其作用相当于一个副词。with care =carefully ﹡with difficulty=difficultly ﹡with warmth=warmly﹡with curiosity=curiously ﹡ with pride=proudly

十、with的复合结构表行为方式或伴随情况

1、with + n/pron + adj.He left the room with the door open.门开着，他就离开了屋子。Don’t talk with your mouse full.嘴里满是东西时不要说话。

2、with + n/pron + adv.With the radio on ,grandma slept deeply in the chair.收音机开者，奶奶在椅子里沉沉的睡着。

With Tom away , I always feel lonely.汤母不在，我一直感觉孤独。

3、with + n/pron + done

The fellow stood there with his hands crossed.这个家伙两手交叉，站在那里。

The peasants have a good harvest with all the crops got in.庄稼都收割了，农民们有了一个好收成。

4、with + n/pron + to do

With this book to help you , you can finish your work as soon as possible.有这本书来帮忙，你能尽快完成工作。

With so many problems to settle ,the new manager was too worried to eat anything.有着太多问题要去处理，新经理担忧的吃不下任何东西。

5、with + n/pron + n

The old man looks down upon everyone ,with his son chairman of the company.因为他儿子是公司的主席，这个老头瞧不起任何人。

He was taken to hospital with his legs a mass of bleeding flesh.他被抬到医院，他的腿血肉模糊。

6、with + n/pron + 介词短语

The man left the meeting with a book in his hand.这个男人手里拿着书离开了会议。

The woman with a diamond necklace around the neck must be wealthy.那个脖子上带项链的女人一定很有钱。

十、with其他用法主要出现在一些常用词和习语中，记住其特定含义即可。如： It is a long time not to get in touch with Tom.很长时间没有和汤母取得联系了。

Down with imperialism.打倒帝国主义。

第四篇：with用法小结

with用法小结

一、with表拥有某物

1、Mary married a man with a lot of money.马莉嫁给了一个有着很多钱的男人。

2、I often dream of a big house with a nice garden.我经常梦想有一个带花园的大房子。

3、The old man lived with a little dog on the lonely island.这个老人和一条小狗住在荒岛上。

二、with表用某种工具或手段

1、We can walk with our legs and feet.我们用腿脚行走。

2、He writes with a pencil.他用铅笔写。

3、I cut the apple with a sharp knife.我用一把锋利的刀削平果。

4、Tom drew the picture with a pencil.汤母用铅笔画画。

三、with表人与人之间的协同关系 make friends with sb

talk with sb quarrel with sb

fight with sb play with sb

work with sb

四、with 表原因或理由

1、John was in bed with high fever.约翰因发烧卧床。

2、He jumped up with joy.他因高兴跳起来。

3、Father is often excited with wine.父亲常因白酒变的兴奋。

4、They were wild with joy.他们欣喜若狂。

五、with 表“带来”，或“带有,具有”，在…身上，在…身边之意

1、The girl with golden hair looks beautiful.那个金头发的女孩看起来漂亮。

2、The director will come to the meeting with the leading actor and actress.那个导演将带着男女主角来到会场。

3、Do you have money with you.身上带着钱吗？

4、Take the umbrella with you in case it rains.随身带伞，以防下雨。

六、with表想法，信念，态度与…一致

1、I agree with you on how to deal with it.关于此事如何处理，我同意你的看法。

2、I believe with the headmaster that a good teacher should not only teach a student what to learn but also how to learn it.我相信校长所说，一个好老师不但教学生学什么，而且应教学生怎么去学。

七、with表示让步,“虽有,尽管”

With all his money and fame, he is not happy.有着钱和名誉，他还是不快乐。

八、with表同时，或同一方向，“随着”

1、The temperature of cold-blooded animals change with the temperature of the surroundings.冷血动物的体温随着周围的环境的改变而变化。

2、The big ship is sailing with the wind.这个大船正随风向航行。

3、And with the last words , she turned away.随着最后一句话说完，他转身离开了。

九、“和……在一起”，表示伴随。例如：

1、Can you go to a movie with me? 你能和我一起去看电影吗？

2、He often goes to the library with Jenny.他常和詹妮一起去图书馆。

3、She lives with her son.她和儿子住在一起。

十、“关于，对于”，表示一种关系或适应范围。例如： What’s wrong with your watch? 你的手表怎么了？

十一、“在……方面”。例如：

Kate helps me with my English.凯特帮我学英语。

十二、“随着，与……同时”。例如：

With these words, he left the room.说完这些话，他离开了房间。

十三、包括...在内

1、I like tea with sugar.我喜欢加糖的茶水。

2、China is a country with a long history.中国是一个历史悠久的国家。

十四、中考with词组总结

1、agree with sb/to+V.同意某人的意见／某事

2、be angry with sb.生某人的气

3、be busy with / doing sth.忙于做某事

4、be covered with被……覆盖

5、be fed up with厌倦

6、be friends with对 …… 友好，与 …… 交上朋友

7、be pleased with对……感到高兴

8、be strick with +sb/in +sth对谁／某事严格．

9、begin with从开始

10、come up with赶上,提出

11、communicate with与……交流

12、compare with与……比较

13、deal with处理

14、do with处置, 处理

15、fall in love with[中考]相爱，爱上

16、fill with用……装满

17、get on well with与 ……相处融洽

18、help sb.with sth.帮助某人做某事

19、in line with与 …… 一致，按照

20、make friends with与……交朋友

21、meet with遭遇

22、play with以 …… 为消遣，玩弄

23、quarrel with(和某人)吵架

24、shake hands with与……握手

25、take up with和 …… 交往，忍受，采用

26、talk to / with sb与某人谈话

27、with one's own eyes亲眼(目睹)

28、with pleasure愉快地

29、with the help of /with one's help[中考]在……的帮助下

30、with the purpose of为了

31、work out ＝come up with做出，算出，制定出

32、chat to / with sb.和某人聊天

33、play with snow玩雪

34、with a smile面带笑容

35、in step with与...一致/协调

36、come along＝come with sb.跟上来

37、be popular with sb.受某人欢迎

38、catch up with sb.赶上某人

39、fall in love with sb./sth.爱上什么

40、offer / provide sb.with sth.给某人提供

41、sb.spend sometime with sb.花了多少时间陪谁

42、have a conversation with sb.与...谈话；交谈

43、with the development of industry随着工业的发展

44、play a joke with sb.和某人开玩笑

45、be mad with joy欣喜若狂

46、meet with a storm遇到风暴

47have nothing to do with与...无关

48、be patient with sb.对某人有耐心

49、supply sb.with sth.向某人供应／提供

50、finish with完成，结束

第五篇：it用法小结

小结(2008-12-08 15:57:31)

标签：教育

It用法小结

it在英语语法中属人称代词，意思是“它”，用来指人以外的一切生物和事物。它的用法不仅不简单，而且很复杂。

一、用于指人以外的一切生物、无生命的东西和事情。

一般指说话者心目中已经了解或所指的生物、无生命的东西或事情、没有性别的区分；可以是可数名词，也可以是不可数名词，在句子中既可做主语，也可以作宾语。1．指动物和植物。如：

—Oh，that's Lucy's hat．噢，那是露茜的帽子。

—It looks like a cat！它看上去像只猫！

Where's tea grown？It's grown in the southeast of China．

什么地方种植茶？中国东南部种植茶。2．指代一些无生命的东西。如： Is it your watch？这是你的手表吗？

Look at the rain！It's heavy，isn't it？看这雨！雨很大，对吗？ 3．代替上文提到过的整个事情。如：

Well，you mustn't play on the road．It's dangerous．哦，你不能在公路上玩。这太危险了！It was hard work，but they really enjoyed it．摘苹果是艰苦活，可他们都乐意去干（它）。

二、用于指代人。

1．指代说话者心目中不太清楚的那个人，常在打电话或敲门时用。如：

—Who was it？是谁（打来的电话）？ —Was it Susan？（打电话的）是苏珊吗？

—Yes，it was．是的，我是。（根据上下句，“it was”也可不译出来。）再如：—Who is knocking at the door？谁在敲门？

—It's me．是我。

2．指说话者心目中的那个人。如：

—Is it your sister，Kate？（那旧照片上的 baby）是你姐姐凯特吧？

—No！不是。

—Is it your brother？是你哥哥吧？

—No！不是。

—I know—it's you！我知道了，（那）是你。

3．指代性别不详的婴幼儿或在不计较性别时，也可用it来指人。如 The child smiled when it saw its mother．这小孩一见到母亲就笑了。I don't know who it is．我不知道他是谁。注意：看到这样的句子（或听到这样的话）时，要想一想，不要一看到it就把它译成“它”。）4．在回答用指示代词表示人的特殊问句时，常用it指人。如：

—Who's that？那人是谁？

—Is it Kate？是凯特吗？

—Yes，I think you're right．It's Kate．是的，我想你说对了，是凯特。

三、用于指时间、距离和自然现象等。1．表示时间。如：

—What time is it？几点钟？

—It's ten．十点钟。

It's summer in Australia now．现在澳大利亚是夏天。特别注意it用于表示时间时还常见于以下两个句型中：（1）It's time（for sb．）to do sth．／It's time for sth．译为“是（某人）该干„„的时间了”、“到„„的时候了”。如：

It's time for supper／to have supper．是吃晚饭的时候了。

I think it's time for us to start the lesson now．我想现在是我们开始上课的时候了。

（2）It is ／has been ＋时间段＋since ＋一般过去时。译为“自从„„以来已过了„„（时间）”。此结构可以与另一种句型进行同义句转换。如：

It has been two weeks since we met last．＝ Two weeks has passed since we met last．自从我们上次相遇以来，两个星期过去了。

It's three years since he came here．＝It has been three years since he came here．＝He has been here for three years．他到这里已经三年了。2．表示距离。如：

It's half an hour's walk from my home to the school．从我家到学校步行得花半小时时间。

—Where's the farm，Li Lei？Is it far？李雷，农场在哪里？远吗？

—No，it's quite near．不，（距）离这很近。3．表示自然现象。如：

Sometimes it snows and the land is all white．有时下雪，大地一片白。It is very quiet here at the moment．眼下这儿很安静。

四、用作形式主语。

英语中常常见到某个句子以it开头，it与其后面的动词不定式短语、动名词短语、名词性从句等相呼应，以表达一个完整的意义。这是一种习惯表达法，这样的句式可避免句子显得头重脚轻。

1．It＋is／was＋形容词＋（for／of sb．）＋动词不定式短语。对于这个句型中究竟用 for还是用of，一般遵循这样的规则：如果形容词仅仅是描述事物的形容词，如：difficult，easy，hard，important，dangerous等用for；如果形容词是描述不定式行为者的性格、品质的，如：kind，good，nice，clever等则用of。如：

It is interesting to play with snow in winter． 冬季里玩雪是很有趣的。

It's important for us to keep the water clean．保持水质清洁对我们来说是很重要的。It's very kind of you to say so．你这样说真是太好了。注意：这一句式中的形容词位置也可换用名词；连系动词be也可换用其它连系动词，如feel等。如：

It's a good habit to get up early and go to bed early．早睡早起是好习惯。

It must be great fun to fly to the moon in a spaceship．乘宇宙飞船飞往月球一定很有趣。It feels strange to have a twin sister．有个孪生姐妹感觉很奇怪。2．It ＋will be／is ／was ＋形容词＋动名词短语。如： It's bad playing in the street．在街上玩是没好处的。Is it any good trying again？再试一次有用吗？ 3．It＋is／was＋形容词＋从句。如：

It is certain that he will come．他一定会来。It's true that he may fall behind the other students．他真的可能落后于其他同学。It is strange that he should say so．他居然这么说，真是奇怪。

4．It ＋is ／was ＋one's turn（duty，pleasure）＋to do sth．意为“该轮到某人做某事（做某事是某人的责任、愉悦的事）”。如：

It's your turn to be on duty tomorrow．明天轮到你值日了。5．It takes（sb．）some time to do sth．意为“（某人）花„„时间做某事”。如 It took me a week to finish reading the book．我花了一周时间看完这本书。

6．It ＋cost／costs ＋sb．＋some money ＋to do sth．译为“某人花多少钱做某事”。如： It cost me 260 yuan to buy the new watch．我买这块新手表花了260元。7．It seems ／seemed ＋从句。译为“看起来好像„„”，此结构可以转换成“seem ＋动词不定式”形式。如：

It seems that he is ill．＝He seems to be ill．看起来他好像病了。

[原题再现] ①________is a fact that English is being accepted as an international language.A.There B.This C.That D.It ② In fact________ is a hard job for the police to keep order in an important football match.A.this B.that C.there D.it 答案: ① D ② D

五、用作形式宾语。

当句子的真正宾语是动词不定式、动名词或从句时，为避免句子头重脚轻，须将其放在宾语补足语之后，改用先行词it占据其原来的位置。it用作形式宾语的句型为：主语＋谓语＋it＋宾语补足语＋动词不定式／动名词／从句。该句型中宾语补足语可由形容词、名词等充当。如：

He found it not easy to learn a foreign language well．他发现学好一门外语是不容易的。We think it no good reading in bed．我们认为躺在床上看书无益处。I think it necessary that we have the meeting．我认为开这个会是必要的。[原题再现] Don't ________that all those who get good grades in the entrance examination will prove to be most successful.A.take as granted

B.take this for granted C.take that for granted

D.take it for granted 答案: D

六.构成强调句。如：

It was in the street that I saw Li Ping this morning.今天早晨，就是在街上我看见李明。[原题再现] ________was in 1979________I graduated from university.A.That;that B.It;that C.That;when D.It;when 答案: B 七.构成特殊句式。如：

It seems as if we should finish it tomorrow.【练习】

（1）There is a photo on the wall.____ the photo of Lei Feng.A.It B.Its C.It's D.He（高考，1980)（2)Is＿necessary to tell his father everything? A.it B.that C.what D.he(MET1987)(3)Is＿possible to fly to the moon in a spaceship? A.now B.man C.that D.it(4)I consider____ my duty to help you． A.it B.this C.that D.its(5).It was at four o'clock in the afternoon ____ he and his grandpa reached the museum in Guanghan.A.while B.that C.when D.as 答案：(1)C(2)A(3)D(4)A(5)B(6)．I like ____ in the autumn when the weather is clear and bright.（2004全国I）A.this B.that C.it D.one(7).-Do you like ___ here?-Oh，yes.The air，the weather，the way of life.Everything is so nice.（2004全国II）A.this B.these C.that D.it(8)．The Parkers bought a new house but ____ will need a lot of work before they can move in.A.they B.it C.one D.which(9).I hate___ when people talk with their mouths full.A.it B.that C.these D.them(10).Joan had often heard____ said that Marley had no money.A.it B.this C.that D.one 答案：C D B A A

八、it, one和that作替代词的用法及区别

it, one和that虽然都可以用来替代前面所提到的一个单数名词,以避免重复,但在具体用法上却有不同。简述如下: 1.it代替前面提到的同一事物,该事物既可以是可数名词也可以是不可数名词。[原题再现] The news that they failed their driving test discouraged him, ______? A.did they B.didn't they C.did it D.didn't it 答案: D 2.one代替前面提到的同类事物中的一个。该事物只能是可数名词,前面可以有冠词,也可以被this、that或形容词修饰,其后也可以有定语。[原题再现]-Why don't we have a little break?-Didn't we just have________? A.it B.that C.one D.this 答案: C 3.that代替前面提到的同类事物中特指的一个。该事物既可以是可数名词也可以是不可数名词,要有后置定语,但不可以有前置修饰语。[原题再现] Few pleasures can equal ________ of a cool drink on a hot day.A.some B.any C.that D.those 答案: C

高考“it”的用法英语题

历届高考英语单项选择题精选

（一）“it”的用法

1.Was it during the Second World War_____ he died?

A.that

B.while

C.in which

D.then

(88)2.Is ____ necessary to complete the design before National Day? A.this

B.that

C.it

D.he

(89)3.I dont think ____ possible to master a foreign language without much memory work.A.this

B.that

C.its

D.it

(91)4.Does ______ matter if he can’t finish the job on time? A.this

B.that

C.he

D.it

(91)5.It was not _____ she took off her glasses _____ I realized she was a famous film star.A.when , that B.until , that C.until , that D.when , then

(92)6.I was disappointed with the film.I had expected ______ to be much better.A.that

B.this

C.one

D.it

(93)7.It was not until 1920 ______ regular radio broadcasts began.A.while

B.which

C.that

D.since

(94)8.______is a fact that English is being accepted as an international language.A.There

B.This

C.That

D.It

(95)9.It was only when I reread this poems recently _____ I began to appreciate their beauty.A.until

B.that

C.then

D.so

(97)10.I hate _____ when people talk with their mouths full.A.it

B.that

C.these D.them

(98)11.It is the ability to do the job _____ matters not where you come from or what you are.A.one

B.that

C.what

D.it

(2000)KEYS: 1-5 ACDDB 6-10 DCDBA 11 B

’