用C++编写：在程序中先声明int,float,char,double型的变量,再声明int,float,char,double类型的指针变量，并用相应存储空间初始化指针变量，分别显示这些指针变量占了多少字节，指针变量所指的变量占了多少字节。（提示用sizeof运算符）

下面是实现代码：

#include <iostream>
using namespace std;

int main() {
    int i = 10;
    float f = 3.14;
    char c = 'A';
    double d = 2.718;

    int* pi = &i;
    float* pf = &f;
    char* pc = &c;
    double* pd = &d;

    cout << "The size of int pointer is: " << sizeof(pi) << " bytes" << endl;
    cout << "The size of float pointer is: " << sizeof(pf) << " bytes" << endl;
    cout << "The size of char pointer is: " << sizeof(pc) << " bytes" << endl;
    cout << "The size of double pointer is: " << sizeof(pd) << " bytes" << endl;

    cout << "The size of int variable pointed by pi is: " << sizeof(*pi) << " bytes" << endl;
    cout << "The size of float variable pointed by pf is: " << sizeof(*pf) << " bytes" << endl;
    cout << "The size of char variable pointed by pc is: " << sizeof(*pc) << " bytes" << endl;
    cout << "The size of double variable pointed by pd is: " << sizeof(*pd) << " bytes" << endl;

    return 0;
}

输出结果为：

The size of int pointer is: 8 bytes
The size of float pointer is: 8 bytes
The size of char pointer is: 8 bytes
The size of double pointer is: 8 bytes
The size of int variable pointed by pi is: 4 bytes
The size of float variable pointed by pf is: 4 bytes
The size of char variable pointed by pc is: 1 bytes
The size of double variable pointed by pd is: 8 bytes

可以看到，指针变量的大小都是8字节（64位系统），因为它们存储的是地址，而地址的大小与机器有关。而指针变量所指的变量大小分别是4字节、1字节和8字节，与它们的类型有关。