jQuery火箭图标返回顶部代码

一>

#include "stdafx.h"
#include<iostream>
#include<string>
#include<fstream>
using namespace std;

class Rectangle
{
private:
    double length, width;
public:
    Rectangle(double l, double w);
};


Rectangle::Rectangle(double l, double w) :length(l), width(w)
{}

int main()
{
    Rectangle rect(20.0, 10.3);
    ofstream out("a.dat", ios_base::binary);     //文件的输出
    if (out.is_open())                           //如果打开成功
    {
        out.write((char*)&rect, sizeof(Rectangle));//把Rectangle类的rect成员写入
        out.close();                             //注意:此步一定不能省
    }
    char* buf = new char[sizeof(Rectangle)];     //缓冲区
    ifstream in("a.dat", ios_base::binary);      //文件的写入
    if (in.is_open())                            //如果文件打开成功
    {
        in.read(buf, sizeof(Rectangle));         //从in指定的已打开文件中读取Rectangle字节到buf中
        in.close();                              //注意:此步一定不能省
    } 
    return 0;
}

结果(注意:.dat文件要用WinHex打开，网上有下载):

二>

#include "stdafx.h"
#include<iostream>
#include<string>
#include<fstream>
using namespace std;

class Rectangle
{
private:
    double length, width;
public:
    Rectangle(double l, double w);
    void displayArea() { cout << length * width << endl; }
};


Rectangle::Rectangle(double l, double w) :length(l), width(w)
{}

int main()
{
    int a[] = { 6,8,2,1 };
    Rectangle rect(20.0, 10.3);
    ofstream out("a.dat", ios_base::binary);
    if (out.is_open())
    {
        out.write((char*)&rect, sizeof(Rectangle));
        out.write((char*)a, 4 * sizeof(int));  //对数组来说，数组有n个元素那么后面就是n*sizeof(int)
        out.close();
    }
    char* buf = new char[sizeof(Rectangle)];
    char* buf2 = new char[4 * sizeof(int)];
    ifstream in("a.dat", ios_base::binary);
    if (in.is_open())
    {
        in.read(buf, sizeof(Rectangle));
        in.read(buf2, sizeof(int) * 4);
        int *a = new int[4];
        memcpy(a, buf2, 4 * sizeof(int));
        cout << a[3] << endl;
        delete[] a;
        in.close();

        Rectangle* pr = (Rectangle*)buf;
        pr->displayArea();
    }
    delete[] buf;
    return 0;
}

结果:

三>

#include "stdafx.h"
#include<iostream>
#include<string>
#include<fstream>
using namespace std;

class Rectangle
{
private:
    double length, width;
public:
    Rectangle(double l, double w);
    void displayArea() { cout << length * width << endl; }
};


Rectangle::Rectangle(double l, double w) :length(l), width(w)
{}

int main()
{
    fstream file("a.txt", ios_base::out | ios_base::app);
    if (file.is_open())
    {
        file << "Hello world!";
        file.close();

    }
    file.open("a.txt", ios_base::in);
    if (file.is_open())
    {
        while (file.good())
        {
            string words;
            file >> words;
            cout << words << " ";
        }
        file.close();
        cout << endl;
    }
    return 0;
}

结果:(文件中与命令提示框输出得一样哦)