1、章2算法框图的基本结构及设计1.掌握循环结构的有关概念.2.理解循环结构的基本模式，会用循环结构描述算法.3.体会循环结构在重复计算中的重要作用.学习目标知识梳理 自主学习题型探究 重点突破当堂检测 自查自纠栏目索引 知识梳理 自主学习知识点一常量与变量的概念答案1.循环结构的定义在一些算法中，经常会出现从某处开始，按照一定的条件 某些步骤的情况，这就是循环结构.反复执行的步骤称为 .2.循环结构的特点(1)重复性：在一个循环结构中，总有一个过程要重复一系列的步骤若干次，而且每次的操作完全相同.(2)判断性：每个循环结构都包含一个判断条件，它决定这个循环的执行与终止.(3)函数性：循环变量在构
2、造循环结构中起了关键作用，蕴含着函数的思想.反复执行循环体答案3.设计一个算法的算法框图的步骤(1)用 表述算法步骤；(2)确定每一个算法步骤所包含的 ，并用相应的算法框图表示，得到该步骤的算法框图；(3)将所有步骤的算法框图用流程线连接起来，并加上，得到表示整个算法的算法框图.自然语言逻辑结构终端框答案思考(1)循环结构的算法框图中一定含有判断框吗？答循环结构的算法框图中一定含有判断框.(2)任何一个算法的算法框图中都必须含有三种基本逻辑结构吗？答不一定.但必须会有顺序结构.知识点二循环结构的设计过程循环结构的算法框图的基本模式，如图所示.返回 题型探究 重点突破题型一循环结构的识别与解读解
3、析答案例1(1)当m7，n3时，执行如图所示的算法框图，输出S的值为()A.7 B.42 C.210 D.840 解析算法框图的执行过程如下：m7，n3时，mn15，km7，S1，S177；kk165，S6742；kk155，S542210；kk140，x532，x20，x231.y0.512.2课堂小结1.(1)循环结构是指在算法中需要重复执行一条或多条指令的控制结构；(2)在循环结构中，通常都有一个起循环计数作用的变量；(3)循环变量、循环体、循环终止条件称为循环结构的三要素.2.画算法框图要注意：(1)使用标准的框图符号；(2)框图一般按从上到下、从左到右的方向画；(3)除判断框外，大多
4、数框图符号只有一个进入点和一个退出点，判断框是具有超过一个退出点的唯一符号；(4)一种判断是“是”与“否”两分支的判断，而且有且仅有两个结果，另一种是多分支判断，有几种不同的结果；(5)在图形符号内描述的语言要非常简练、清楚.返回团Tiffany，a 16yearold girl，was very shy.Last September，her best frien“I was really sad the moment I heard the bad news and I didnt know what to do，”Tiffany recalled.“I shut myself in my
5、room for a whole week.It was then that my aunt took me to a sports club one Saturday and I saw so many young people playing different kinds of sports there.I signed up for a beginners course in volleyball and since then I have been playing this sport.Now I practice twice a week there.It is wonderful
6、 playing sports in this club and I have made lots of friends as well.2 ”The most basic aim of playing sports is that you can improve your health even if you are not very good at sports.Besides，you can get to know a circle of people at your age while playing sports.3 Since she joined the sports club，
7、s I got used to the life here.And now I know lots of(5)_ here.For example,when I meet my friend on the street,I usually(6)_ him like this,“Hey,where are you going?”In our country if someone asks this,people may get(7)_ but in this country people wont.Of course,there are some other interesting things
8、 here.Ill tell you about them next time.he has opened up herself and now she has become very active and enjoys meeting and talking with others.1Its polite for girls to kiss each other on the side of the face.s also become more confident.团圆圆一家在台湾可受欢迎了。每天，小朋友们排着长队，等着跟它们合影留念。从“排着长队”体现出每天喜欢它们的人不计其数，特别受选D.A.根据同类项合并法则,与不是同类项,不能合并,故本选项错误;B.根据算术平方根的定义,=3,故本选项错误;C.根据同底数幂的乘法aa2=a3,故本选项错误;D.根据积的乘方,(2a3)2=4a6,故本选项正确.欢迎。从“合影留念”体现出大家都想和大熊猫留住最美丽的瞬间以作纪念。Nothing can be accomplished without norms or standards.精品资料！感谢阅读下载！
