C++基础--结构体声名

struct是一种数据结构，当需要存储的相关数据为一个集合时，struct是很好的选择;例如，当存储student，学生的学号， 名字，年龄，身高，就构成了一个集合，用stuct声名为：

typedef struct chemical_student_for_uni{
    char name[32];
    int card_id;
    int age;
    int height;
}student_c;

struct指名了这个是chemical_student_for_uni结构，typedef为这个结构起了一个别名student_c, 那么就可以使用student_c来代替struct chemical_student_for_uni的结构；

顺便提一下typedef的用法：

1. 隐藏数据的类型，例如给类型取别名;

2. 简化类型定义，同时便于理解;

struct的存储:struct的成员是按照声名的顺序进行存储的，假设student_c存储在内存中的地址为100, 以上student在内存中的存储形式如下：

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" 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struct结构嵌套：

struct 结构标记｛
    类型 成员名；
    类型 成员名；
    struct 结构标记｛
        类型 成员名；
        类型 成员名；
        ...
    ｝结构变量名；
｝结构变量名；

无结构标记的结构变量:

struct｛
    类型 成员名；
    类型 成员名；
    ...
｝结构变量名；

以下为结构的例子：

（1）当无结构标记的结构变量声明，例如student_1的声明：

struct {/*无结构标记*/
    char name[];
    int card_id;
    int age;
    int height;
}student_1;

（2）有结构标记的结构变量声明：

结构定义：

struct student{
    char name[];
    int card_id;
    int age;
    int height;
};

结构变量声明：struct student student_1;

（3）有结构标记的结构变量student_1的声明：

struct student{
    char name[];
    int card_id;
    int age;
    int height;
}student_1;

（4）带有typedef的无结构标记的声明：

定义别名:

typedef struct {
    char name[];
    int card_id;
    int age;
    int height;
}student_c;

定义结构变量名：student_c student_1;

（5）带有typedef的有结构标记的声明：

定义别名:

typedef struct student{
    char name[32];
    int card_id;
    int age;
    int height;
}student_c;

当定义时，可以直接使用别名：student_c student_1;