#include<iostream.h>
//聲明全局變量并初始化
extern int a[]={1,2,3};
extern float p=3.14;

//在show()函數中使用外部變量
show()  {
    int i;
    cout<<"In show():"<<endl;
	cout<<"p="<<p<<endl;
	cout<<"a[]: ";
    for (i=0;i<=2;i++) 
        cout<<a[i]<<"  ";
    cout<<endl;
    //cout<<"y="<<y<<endl; 編譯出錯！
}

//聲明外部變量并初始化
int y=5678;

//在main()函數中使用外部變量
main()  
{
    //聲明局部變量
    int i,p=100;

    //顯示重名變量
	cout<<"In main():"<<endl;
    cout<<"p="<<p<<endl;

    //顯示全局變量
    cout<<"::p="<<::p<<endl;
	cout<<"a[]: ";
    for (i=0;i<=2;i++)
        cout<<a[i]<<"  ";
    cout<<endl;
    cout<<"y="<<y<<endl;   //編譯正確！

    show();  //調用函數
}