菜鸟的虚函数有关问题，马上给分！

初学者的虚函数问题，马上给分！！
先建一个抽象类Vehicle，再从其派生出car,truck二个类，在最后的文件中定义一个打印函数，输出其内容，但出错了，请高手帮忙看看，错在哪里？在线等，马上给分！！
//15.5.h
#include <iostream.h>
class   Vehicle
{
public:
Vehicle(char   *);
virtual   ~Vehicle();
virtual   void   show()   const=0;
protected:
char   *name;
};
///////////////////////////////////////
//15.5.cpp
#include <iostream.h>
#include <string.h>
#include "15.5.h "
Vehicle::Vehicle(char   *na)
{
name=new   char[strlen(na)+1];
strcpy(name,na);
}

Vehicle::~Vehicle()
{
delete   []   name;
}
///////////////////////////////////////
//15.5_1.h
#include <iostream.h>
#include "15.5.h "
class   car   :public   Vehicle
{
public:
car(char   *,int);
~car();
void   show()const;
private:
int   pl;
};
/////////////////////////////////////////
//15.5_1.cpp
#include <iostream.h>
#include "15.5_1.h "
car::car(char   *vname,int   a):Vehicle(vname)
{
pl=a;

}
car::~car()
{
cout < < "the   object   of   car   is   delete " < <endl;
}

void   car::show()
{
cout < < "the   car 's   name   is: " < <name < <endl
< < "pl: " < <pl < <endl;
}

/////////////////////////////////////////////
//15.5_2.h
#include <iostream.h>
#include "15.5.h "
class   truck   :public   Vehicle
{
public:
truck(char   *,char   *);
~truck();
void   show()const;
private:
char   *color;
};

///////////////////////////////
//15.5_2.cpp
#include <iostream.h>
#include <string.h>
#include "15.5_2.h "
truck::truck(char   *tname,char   *tcolor):Vehicle(tname)
{
color=new   char[strlen(tcolor)+1];
strcpy(color,tcolor);
}
truck::~truck()
{
delete   []   color;
}

void   truck::show()
{
cout < < "the   truck 's   name   is: " < <name < <endl
< < "color: " < <color < <endl;
}
/////////////////////////////////
//15.5_3.cpp
#include <iostream.h>
//#include "15.5.h "

#include "15.5_1.h "
#include "15.5_2.h "
void   schoolshow(Vehicle   &);
int   main()
{
car   vcar( "Benz ",500);
truck   vtruck( "Ferrari ", "yellow ");
schoolshow(vcar);
schoolshow(vtruck);
return   0;
}

void   schoolshow(Vehicle   school)
{
school.show();
}

------解决方案--------------------
void schoolshow(Vehicle& school)
{
school.show();
}
------解决方案--------------------
#include "15.5_1.h "
#include "15.5_2.h "

这两个头文件都包含了 “15.5.h” 这个头文件，因此 Vehicle 这个类重复定义了。
------解决方案--------------------
void car::show()cosnt
{
cout < < "the car 's name is: " < <name < <endl
< < "pl: " < <pl < <endl;