C++第一章1-基本数据与表达式

第第11章章基本数据与表达式基本数据与表达式1.1概述1.2C++的字符集与词汇1.3C++的基本数据类型与存储形式1.4数据对象与访问1.5表达式1.6数据输入和输出小结程序设计语言人指挥计算机工作的工具，是由字、词和语法规则构成的指令系统程序设计根据特定的问题，使用某种程序设计语言，设计出计算机执行的指令序列主要完成两方面工作：(1)数据描述（2）数据处理1.1.1程序设计与程序设计语言1.11.1概述概述问题：输入圆的半径，求圆的周长和面积数据描述：半径，周长，面积均用实型数表示数据处理：输入半径r；计算周长=2*π*r；计算面积=π*r2；输出半径，周长，面积；1.1.2一个简单的C++程序1.11.1概述概述例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}数据描述例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}数据处理例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}输入数据例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}计算周长和面积例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}输出计算结果例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}注释行例例11--11方法一,用结构化方法编程，求圆的周长和面积#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}////countthegirthandareaofcircle////thisisasimpleprogram注释第一种形式:以”//”开始至行末注释第一种形式:以”//”开始至行末例例11--11方法一,用结构化方法编程，求圆的周长和面积#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}/*/*thisisasimpleprogramcountthegirthandareaofcircle*/*/注释第一种形式:以”//”开始至行末注释第一种形式:以”//”开始至行末第二种形式:/*字符串*/第二种形式:/*字符串*/例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}预编译指令在程序编译之前把指定文件内容复制到此处例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}使用标准命名空间例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}函数头例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}函数返回值类型main函数一般用int类型例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}函数名main主函数名，系统预定义例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthendl;coutarea=areaendl;}参数表没有参数不能省略圆括号例例11--11方法一,用结构化方法编程，求圆的周长和面积//countthegirthandareaofcircle#includeiostreamusingnamespacestd;intmain(){doubler,girth,area;constdoublePI=3.1415;coutPleaseinputradius:\n;cinr;girth=2*PI*r;area=PI*r*r;coutradius=rendl;coutgirth=girthen