用c++编在程序中先声明int,float,char,double型的变量，再声明 int,rloat,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宇 节。（提示用sizeof运算符）

以下是代码实现：

#include <iostream>
using namespace std;

int main() {
    int a = 10;
    float b = 3.14;
    char c = 'A';
    double d = 2.71828;

    int* ptr1 = &a;
    float* ptr2 = &b;
    char* ptr3 = &c;
    double* ptr4 = &d;

    cout << "Size of int pointer: " << sizeof(ptr1) << endl;
    cout << "Size of float pointer: " << sizeof(ptr2) << endl;
    cout << "Size of char pointer: " << sizeof(ptr3) << endl;
    cout << "Size of double pointer: " << sizeof(ptr4) << endl;

    cout << "Size of int variable pointed by ptr1: " << sizeof(*ptr1) << endl;
    cout << "Size of float variable pointed by ptr2: " << sizeof(*ptr2) << endl;
    cout << "Size of char variable pointed by ptr3: " << sizeof(*ptr3) << endl;
    cout << "Size of double variable pointed by ptr4: " << sizeof(*ptr4) << endl;

    return 0;
}

输出结果：

Size of int pointer: 8
Size of float pointer: 8
Size of char pointer: 8
Size of double pointer: 8
Size of int variable pointed by ptr1: 4
Size of float variable pointed by ptr2: 4
Size of char variable pointed by ptr3: 1
Size of double variable pointed by ptr4: 8

解释：

- `sizeof` 运算符返回变量或类型所占用的字节数。
- `int`, `float`, `char`, `double` 分别占用 4 字节、4 字节、1 字节、8 字节。
- 指针变量占用 8 字节（因为我的机器是 64 位的）。
- 指针变量所指向的变量占用的字节数与变量类型相同。