使用控制符控制输出格式

iomainip 控制符
#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
 int a;
 cout<<"input a:";
 cin>>a;
 cout<<"dec:"<<dec<<a<<endl;                                           //输出a的10进制
 cout<<"hex:"<<hex<<a<<endl;                                           //输出a的16进制
 cout<<"oct:"<<oct<<a<<endl;                                           //输出a的8进制
 cout<<"oct:"<<setbase(8)<<a<<endl;                                    //输出a的8进制
 char *pt="China";
 cout<<setw(10)<<pt<<endl;                                             //域宽为10
 cout<<setfill('*')<<setw(10)<<pt<<endl;                               //域宽为10，空白处用*填充
 cout<<setiosflags(ios::left)<<setw(15)<<pt<<endl;                     //域宽为15，左对齐            
        cout<<setiosflags(ios::right)<<setw(15)<<pt<<endl;                    //域宽为15，右对齐
 cout<<setiosflags(ios::skipws)<<setw(15)<<pt<<endl;                   //域宽为15，空白处忽略
 int b;
        cout<<"input b:";
 cin>>b;
 cout<<"16进制:"<<setiosflags(ios::uppercase)<<setbase(16)<<b<<endl;   //输出a的16进制，输出字母X时以大写表示
 double pi=22.0/7.0;
 cout<<setiosflags(ios::scientific)<<setprecision(8);                  //用科学记数法，精确度为8
 cout<<setiosflags(ios::showpos)<<setiosflags(ios::uppercase);         //输出正数时，给出+，并以科学记数法输出E
 cout<<"pi="<<pi<<endl;
 cout<<"pi="<<setprecision(4)<<pi<<endl;                                //精确度为4
 cout<<"pi="<<setiosflags(ios::fixed)<<pi<<endl;                         //浮点数以固定的小数显示
 return 0;
}