修改一下的代码错误：#include "iostream.h>" class Rectangle //矩形类 { private: int length; //矩形的长 protected: int width; //矩形的宽 public: Rectangle(int l = 10, int w = 10):length(l), width(w) { } int calArea() { return length * width; } }; class Cuboid : public Rectangle //长方体类，从Rectangle公有派生 { private: int height; //长方体的高 public: Cuboid(int l = 10, int w = 10, int h = 10) { length = l; width = w; height = h; } int calVolume() { return calArea() * height; } }; void main(void) { Cuboid test(10, 20, 30); cout << test.calVolume() << endl; }

修改后的代码如下：

#include <iostream>

using namespace std;

class Rectangle   //矩形类 
{ 
private: 
    int length;   //矩形的长 
protected: 
    int width;    //矩形的宽 
public: 
    Rectangle(int l = 10, int w = 10):length(l), width(w)  
    { 
    } 
    int calArea() 
    { 
        return length * width; 
    } 
}; 

class Cuboid : public Rectangle  //长方体类，从Rectangle公有派生 
{ 
private: 
    int height;    //长方体的高 
public: 
    Cuboid(int l = 10, int w = 10, int h = 10): Rectangle(l, w), height(h) 
    { 
    } 
    int calVolume() 
    { 
        return calArea() * height; 
    } 
}; 

int main(void) 
{ 
    Cuboid test(10, 20, 30); 
    cout << test.calVolume() << endl; 
    return 0;
}

修改的部分：
1. iostream头文件应该是#include <iostream>
2. main函数的返回类型应该是int而不是void
3. Cuboid类的构造函数应该调用基类Rectangle的构造函数来初始化基类成员变量
4. main函数中应该有return 0;语句