C++与C语言

#include <iostream>
#include<string>
using namespace std;
struct MM
{
	char name[20];
	int age;
};
int main()
{
	struct MM girl;
	MM mm;//C++中不需要struct关键字
	return 0;
}

#include <iostream>
#include<string>
using namespace std;
struct MM
{
	//属性
	//数据成员
	char name[20];
	int age;
	//行为（方法）
	//成员函数
	void print()
	{
		cout << name << "\t" << age << endl;
	}
	void printData();//在结构体中声明，在外面实现
	int& getAge()
	{
		return age;
	}
};
//结构体名限定，就是告诉别人这个函数来自哪里
void MM::printData()
{
	cout << name << "\t" << age << endl;
}
//结构体中的变量必须要通过结构体变量（结构体指针）访问
//c++结构体中的函数访问属性，可以直接访问
int main()
{
	struct MM girl = {"小芳",28};
	MM mm = {"小丽",24};//C++中不需要struct关键字
	girl.print();
	(&mm)->printData();
	MM* p = &mm;
	p->printData();
	p->getAge() = 84;
	p->printData();
	p->age = 1991;
	p->printData();
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
void testNoeMemory()
{
//申请不做初始化
	int* pInt = new int;
	*pInt = 123;
	cout << *pInt << endl;
	char* pChar = new char;
	*pChar = 'A';
	cout << *pChar << endl;
//申请内存做初始化  ()给单个数据做初始化
	int* pNum = new int(134);
	cout << *pNum << endl;
	delete pInt;
	pInt = nullptr;
	delete pChar;
	pChar = nullptr;
	delete pNum;
	pNum = nullptr;
}
void testArrayMerrmory()
{
	//一维数组
	//1、不带初始化
	//长度可以是h变量，只要值就可以
	int* pInt = new int[3];//等效产生了 int pInt[3]的数组
	char* pstr = new char[15];
	strcpy_s(pstr, 15, "I love you");
	cout << pstr << endl;
	//带初始化的 一堆数据用{}
	int* pNum = new int[3]{1, 2, 3};
	for (int i = 0; i < 3; i++)
	{
		cout << pNum[i] << " ";
	} 
	cout << endl;
	delete[] pNum;
	char* str = new char[20]{'A', 'B', '\0'};
	cout << str << endl;
	delete[] str;
	str = nullptr;
	str = new char[20]{"Ilove you"};
	cout << str << endl;
	delete[] str;
	str = nullptr;
	delete[] pInt;//数组的指针 不需要大小
	//释放只有两种形式 delete 指针 delete [] 指针
	//delete [][] p 没有这种写法
	pInt = nullptr;
}
int main()
{
	testNoeMemory();
	return 0;
}

#include<iostream>
#include<string>
using namespace std;
void testNoeMemory()
{
//申请不做初始化
	int* pInt = new int;
	*pInt = 123;
	cout << *pInt << endl;
	char* pChar = new char;
	*pChar = 'A';
	cout << *pChar << endl;
//申请内存做初始化  ()给单个数据做初始化
	int* pNum = new int(134);
	cout << *pNum << endl;
	delete pInt;
	pInt = nullptr;
	delete pChar;
	pChar = nullptr;
	delete pNum;
	pNum = nullptr;
}
void testArrayMerrmory()
{
	//一维数组
	//1、不带初始化
	//长度可以是h变量，只要值就可以
	int* pInt = new int[3];//等效产生了 int pInt[3]的数组
	char* pstr = new char[15];
	strcpy_s(pstr, 15, "I love you");
	cout << pstr << endl;
	//带初始化的 一堆数据用{}
	int* pNum = new int[3]{1, 2, 3};
	for (int i = 0; i < 3; i++)
	{
		cout << pNum[i] << " ";
	} 
	cout << endl;
	delete[] pNum;
	char* str = new char[20]{'A', 'B', '\0'};
	cout << str << endl;
	delete[] str;
	str = nullptr;
	str = new char[20];
	cout << str << endl;
	delete[] str;
	str = nullptr;
	delete[] pInt;//数组的指针 不需要大小
	//释放只有两种形式 delete 指针 delete [] 指针
	//delete [][] p 没有这种写法
	pInt = nullptr;
}
struct MM
{
	char* name;
	int age;
	void printMM()
	{
		cout << name << "\t" << age << endl;
	}
};
void testStructMerrory()
{
	//new一个对象
	int* p = new int(123);
	//结构体只能用大括号
	MM* pMM = new MM;
	//结构体中指针，要做二次申请，才能strcpy,或者赋值
	pMM->name = new char[20];
	strcpy_s(pMM->name, 20, "李四");
	pMM->age = 188;
	pMM->printMM();
	//申请的顺序和释放的顺序是相反的
	delete[]pMM->name;
	delete pMM;
}
int main()
{
	//testNoeMemory();
	testStructMerrory();
	return 0;
}