9 引用是变量的别名（不能只有别名）

基本数据类型的引用

#include<iostream>
using namespace std;
int main(void)
{
	int a = 3;
	int &b = a;   //引用必须初始化
	b = 10;
	cout<<a<<endl;
	system("pause");   //屏幕停一会儿
	return 0;
}

输出结果：10

结构体类型的引用

#include<iostream>
using namespace std;
typedef struct
{
	int x;
	int y;
}Coor;
int main(void)
{
	Coor c1;
	Coor &c = c1;
	c.x = 10;
	c.y = 20;
	cout<<c1.x<<c1.y;
	system("pause");
	return 0;
}

指针类型的引用

#include<iostream>
using namespace std;
int main(void)
{
	int a = 10;
	int *p = &a;
	int *&q = p;
	*q = 20;
	cout<<a<<endl;
	return 0;
}

引用作函数参数

//c
...
void fun(int *a, int *b)
{
	int c = 0;
	c = *a;
	*a = *b;
	*b = c;
}
...
int x = 10,y = 20;
fun(&x,&y);

//c++
...
void fun(int &a, int &b)
{
	int c = 0;
	c = a;
	a = b;
	b = c;
}
...
int x = 10,y = 20;
fun(x,y);

10 const (不可修改)

“const int *p = NULL;”等价于“int const *p = NULL;”

int * const p = NULL;

“const int * const p = NULL;”等价于“int const * const p = NULL;”

11 有默认参数值的参数必须在参数表的最右端

正确：void fun(int i, int j = 5,int k = 10);
错误：void fun(int i, int j = 5,int k);
eg.

...
void fun(int i, int j = 5, int k = 10);//声明写默认值
void fun(int i,int j,int k)
{
	cout<<i<<j<<k;
}
int main()
{
	fun(20);         //传入 i=20,j=5,k=10
	fun(20,30);      //传入 i=20,j=30,k=10
	fun(20,30,40);   //传入 i=20,j=30,k=40
	return 0;
}

无实参则用默认值，否则实参覆盖默认值

12 申请和释放内存的方法

$$\{\begin{array}{ll}& \text{申请内存 int *p = new int;}\\ & \text{释放内存 delete p;}\end{array}$$
$$\{\begin{array}{ll}& \text{申请块内存 int *arr = new int[10]; //int *arr 数组}\\ & \text{释放块内存 delete []arr;}\end{array}$$
注：释放内存时

...
int*p = new int;
if(NULL == P)
{
	//内存分配失败
	//异常处理
}
delete p;
p = NULL;  //设空指针，否则会导致异常处理