Set the decimal point

#include <iostream>
#include <iomanip>
using namespace std;
int main(){
    int n=16;
    double f=3.1415926535;
    cout<<setbase(8)<<n<<endl;//you can set the input/output system(jin_zhi)by the setbase();
    cout<<setbase(10)<<n<<endl;
    cout<<setbase(16)<<n<<endl;//you can change the case by uppercase a->A;
    cin>>setbase(16)>>n;      //by this way you can easily transform short size input and output;
    cout<<setbase(10)<<n<<endl;     //it‘s the same if you use"dec/hex/oct";
    //set the significant digits,it will round off at the same time
　　 // ps.you can round off by int(n+0.5);
    cout<<setprecision(2)<<f<<endl;
    //set the total decimal digits;
    cout<<fixed<<setprecision(6)<<f<<endl;
    //set the alignment(dui_qi_fang_shi);
    cout<<setw(10)<<left<<1<<endl;//set width
    cout<<setw(10)<<right<<1<<endl;
    //show the dot and zero;
    cout<<showpoint<<3.1200<<endl;
    //scientific form of numbers;
    //it will change the form entirely since it‘s used and I don‘t know how to turn off it......
    cout<<scientific<<f<<endl;
}