C++类（一）

*1. 32位系统中，1个成员变量占4bytes，1个虚函数占4bytes.
2. 成员函数不占内存，不含成员变量和虚函数的类占1byte.
3. new:
Type pointer = new Type; //指针申明和分配内存
delete pointer; //释放内存

#include "pch.h"
#include <iostream>
using namespace std;

class A {
public:
	void A1(void) {}
	void A2(void) {}
	void A3(void) {}
};
class B {
public:
	void B1(void) {}
	void B2(void) {}
	virtual void B3(void) {}
};
class STU {
public:
	int ID;
	float score;
	STU(int x, float y);	/*构造函数*/
	~STU(void);				/*析构函数	*/
	float GetScore(void);
	int GetID(void);
	void SetID(int id);
	void SetScore(float s);
private:
	char money;
	float *ptr;
};
STU::STU(int x, float y)
{
	ID = x;
	score = y;
	ptr = new float;
	*ptr = score;
	cout << "Object is being created" << endl;
};
STU::~STU(void)
{
	cout << "Object is being deleted" << endl;
}
float STU::GetScore(void)
{
	return *ptr;
}
int STU::GetID(void)
{
	return ID;
}
void STU::SetID(int id)
{
	ID = id;
}
void STU::SetScore(float s)
{
	*ptr = s;
}

int main()
{
	STU *tomato;
	tomato = new STU(4, 6);/*注意new的用法*/
	
	printf("sizeof(tomato):%d\n", sizeof(tomato));	
	printf("%d %f\n", tomato->GetID(), tomato->GetScore());/*类指针成员用‘->’*/

	STU hm(1, 2);
	printf("sizeof(hm):%d\n", sizeof(hm));
	hm.SetID(2017);
	hm.SetScore(99.5);
	cout << hm.GetID() << " " << hm.GetScore() << endl;
	printf("sizeof(hm):%d\n", sizeof(hm));/*4个成员函数,32位系统中，一共占32bytes*/

	A aa;
	printf("sizeof(aa):%d\n", sizeof(aa));/*成员函数不占内存，不含成员变量的类占1byte.*/

	B bb;
	printf("sizeof(bb):%d\n", sizeof(bb));/*虚函数占4bytes.*/
}