这代码错在哪，我真的找不出来

#include
using namespace std;
class Rectangle
{
private:
int width,length;
public:
Rectangle(int a,int b)
{
width=a;
length=b;
}
void set_rectangle(int w,int l)
{width=w;length=l;}
int area();
int perimeter();
}
int Rectangle::area()
{
return(width*length);
}
int Rectangle::perimeter()
{
return(2*(width+length));
}
int main()
{
Rectangle r(12,4);
cout<<"this rectangle's area is "<<r.area()<<",perimeter is "<<r.perimeter();
r.set_rectangle(2,4);
cout<<"the new rectangle's area is "<<r.area()<<",perimeter is "<<r.perimeter();
return 0;
}

1. #include 这个后面没有头文件
2. 类定义没有结束符 ;

class 类名
{
public:
//公共的行为或属性

    private:
        //公共的行为或属性
};

    你的类定义缺少最后的“；”

类定义结束时应该加上分号

 #include <iostream>
using namespace std;
class Rectangle
{
private:
    int width,length;
public:
    Rectangle(int a,int b)
    {
        width=a;
        length=b;
    }
    void set_rectangle(int w,int l)
    {width=w;length=l;}
    int area();
    int perimeter();
};
int Rectangle::area()
{
    return(width*length);
}
int Rectangle::perimeter()
{
    return(2*(width+length));
}
int main()
{
    Rectangle r(12,4);
    cout<<"this rectangle's area is "<<r.area()<<",perimeter is "<<r.perimeter();
    r.set_rectangle(2,4);
    cout<<"the new rectangle's area is "<<r.area()<<",perimeter is "<<r.perimeter();
    return 0;
}

http://codepad.org/uywc4qKZ
this rectangle's area is 48,perimeter is 32the new rectangle's area is 8,perimeter is 12

就照大家的意见办吧。写代码时的小遗漏。

要注意细节，头文件，“；”遗漏

缺少分好，，，，小问题啊