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#include <iostream.h> //包含iostream.h头文件 main() {

//声明变量，并初始化 int a=010,b=10,c=0X10;

//以十进制形式显示数据 cout<<"DEC:"; cout<<" a="<<a; cout<<" b="<<b;

cout<<" c="<<c<<endl;

//以八进制形式显示数据 cout<<"OCT:";

cout<<oct; //指定八进制输出 cout<<" a="<<a; cout<<" b="<<b;

cout<<" c="<<c<<endl;

//以十六进制形式显示数据 cout<<"HEX:";

cout<<hex; //指定十六进制输出 cout<<" a="<<a; cout<<" b="<<b;

cout<<" c="<<c<<endl;

//八、十和十六进制数混合运算并输出 cout<<"a+b+c=";

cout<<dec; //恢复十进制输出 cout<<a+b+c<<endl;

//测试八、十和十六进制输入 cout<<"DEC:a="; cin>>a; cout<<"OCT:b="; cin>>b; cout<<"HEX:a="; cin>>c;

cout<<"DEC:"<<dec<<endl; //指定十进制输出 cout<<"a="<<a<<endl; cout<<"b="<<b<<endl; cout<<"c="<<c<<endl; }

cin>>dx; cout<<"dy="; cin>>dy;

cout<<dx<<"+"<<dy<<"="<<dx+dy<<endl; cout<<dx<<"-"<<dy<<"="<<dx-dy<<endl; cout<<dx<<"*"<<dy<<"="<<dx*dy<<endl;

cout<<dx<<"/"<<dy<<"="<<dx/dy<<endl<<endl; //cout<<fx<<"%"<<fy<<"="<<fx%fy<<endl; Error!

//测试float和double类型数据的有效位 fx=10.0;fy=6.0; float fz=fx/fy; dx=10.0;dy=6.0; double dz=dx/dy; cout<<"fz=";

cout<<setprecision(20)<<fx<<"/"<<fy<<"="<<fz<<endl; cout<<"dz=";

cout<<setprecision(20)<<dx<<"/"<<dy<<"="<<dz<<endl<<endl;; //float型溢出 float x=3.5e14;

cout<<"x="<<x<<endl; cout<<"x*x="<<x*x<<endl;

cout<<"x*x*x="<<x*x*x<<endl; }

#include <iostream.h> main() {

//x,y 为操作数，c为运算符 int x,y,z; char c1;

cin>>x>>c1>>y; //c1

//多路选择语句选择不同表达式计算语句 switch(c1) {

case '+':cout<<x<<"+"<<y<<"="<<x+y<<endl; break;

case '-':cout<<x<<"-"<<y<<"="<<x-y<<endl; break;

case '*':cout<<x<<"*"<<y<<"="<<x*y<<endl; break;

case '/':cout<<x<<"/"<<y<<"="<<x/y<<endl; break;

case '%':cout<<x<<"%"<<y<<"="<<x%y<<endl; break;

default :cout<<"Wrong !"<<endl; //当不符合上述情况时执行本子句 } }

#include<iostream.h>

float x=365.5; //声明全局变量 main() {

int x=1,y=2; double w=x+y; {

double x=1.414,y=1.732,z=3.14; cout<<"inner:x="<<x<<endl; cout<<"inner:y="<<y<<endl; cout<<"inner:z="<<z<<endl; cout<<"outer:w="<<w<<endl;

cout<<"::x="<<::x<<endl; //访问重名的全局变量 }

cout<<"outer:x="<<x<<endl; cout<<"outer:y="<<y<<endl; cout<<"outer:w="<<w<<endl;

//cout<<"inner:z="<<z<<endl;无效

cout<<"::x="<<::x<<endl; //访问重名的全局变量 }

#include<iostream.h> main() {

//显示1,2,3...10