1.数组

类似Java中的数组

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unsigned int name[10] = {};
name[1] = 9;
name[3] = 1;
cout << sizeof name / sizeof (int);//获取数组长度

２.字符串

(1)char数组形式：

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char name;
char fish[] = "Bubbles";
size_t len = strlen(fish);
cin >> name;
cout << "name is" << name << endl << "length is" << len;

(2)string形式：

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string str1 = "father";
char first_data[] = {"Le Chapon Dodu"};
string second_data = {"The Bread Bowl"};

char charr[20] = "jaguar";
string str = charr;

string str3 = str1 + str;

char ca1[20];
char ca2[20] = "jagur";
strcpy(ca1, ca2); //copy ca2 to ca1;
strcat(ca1, "juice"); // add juice to end of ca1
unsigned long len1 = str.size(); // return size
size_t len2 = strlen(ca1); // return size
wchar_t title[] = L"chief";
char16_t names[] = u"felonia";
char32_t car[] = U"Humer";

３．结构属性：

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void test() {
    user person1 = {
            "haha",
            3.2f,
            2.5
    };
    cout << person1.name << endl;

    user persons[] = {};
    user people[2] = {
            {"bami", 1.1f, 1.99},
            {"God",  2.3f, 3.5}
    };
    if (person1.name == "haha"){
        //...
    }
}

struct user {
    char name[20];
    float volume;
    double price;
};

４．共用体用法和结构属性相同，但是只能同时存储其中一种类型(int、long、double)

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    cout << person1.id_val.id_char; 

struct user {
    char name[20];
    float volume;
    double price;

    union id{
        long id_num;
        char id_char[20];
    } id_val;
};

５.enum类型

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void test_color() {
    color band;
    band = yellow;
    int col = black;
    col += 1;

    bits mybit = bits(2);
}

enum color {
    red, orange, yellow, green, blue, black, purple
};

enum bits {　
    one = 1, two = 2, three = 3, four = 4
};

６.指针

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void point() {
    int updates = 6; // 声明变量
    int *p_update; // 声明int类型指针
    p_update = &updates;//声明指针指向的地址

    cout << "updates = " << updates;              //6
    cout << "*p_update = " << *p_update << endl;  //6

    cout << "Address = " << &updates << endl;     //0x7ffd813aebe4
    cout << "Address = " << p_update;             //0x7ffd813aebe4

    int *pt;
    pt = (int *) 0xB8000000;

    int *pn = new int; //只能通过指针访问值
    int higgens;
    int *ps = &higgens; //可通过变量和指针访问
}

７．delete和new

delete只能用来释放new 分配的内存,delete后加上指向内存块的指针。

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int *ps = new int;
delete ps;

int *psom = new int [10];
psom[5] = 10;
delete [] psom;

８．指针算数

C++允许将指针和整数相加，加１的结果等于原来的地址值加上指向的对象占用的字节数。

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int as[3] = {1,2,3};
int *aw = as;

cout << *aw; //默认取第一个
aw = aw +1;  //1
cout << *aw;  //2

因为int类型指针加１相当于把地址值增加了8,这使得aw的值为第二个元素的值。

9.存储类型

（１）自动存储：函数内部定义的常规变量使用自动存储空间，称为自动变量。自动变量存储在栈中（后进先出）

（２）静态存储：整个程序执行期间都存在的存储方式。可使用在函数外部定义或者static。

（３）动态存储：new和delete运算符提供了一种比自动变量和静态变量更灵活的方法。管理了一个内存池，称为堆。内存管理更加复杂和灵活。

10.使用vector和array代替数组

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vector<double> ve(8);
vector<int>vi;
ve[2] = 2.4;


array<double ,4> ad = {1.1,2.3,1.4,3.2};
array<int,5>ai{};
ai[2] = 2;
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