两个值按大小交换没成功

这是一个随便输入10个数  然后升序输出的程序
我想问下为啥没交换？  怎么改？  谢谢
#include<iostream>
#include<iomanip>
using namespace std;
int main()
    {
    int i,j,temp,a[11];
    cout<<"enter data:"<<endl;
    for(i=1;i<=10;i++)
        {
        cout<<"a["<<i<<"]=";
        cin>>a[i];
        }
    cout<<endl<<"The original numbers:"<<endl;
    for(i=1;i<=10;i++)
        cout<<a[i]<<" ";
    cout<<endl;
    for(i=1;i<=9;i++)
        {
        for(j=i+1;j<=10;j++)
            if(a[i]>a[j])
            {
            temp=a[i];
            a[i]=a[j];
            a[i]=temp;
            }
        }

    cout<<endl<<"The sorted numbers:"<<endl;
    for(i=1;i<=10;i++)
        cout<<a[i]<<" ";
    cout<<endl;
    return 0;
}