C language struct definition

C language struct definition

1 Structure statement

struct  Book
{
        char name[100];    //书名
        float price;           //价格
}b1,b2;                       //全局变量

struct Book b3;            //全局变量   
//上面两种表示方式是相同的意思

int main()
{
    struct Book b5;           //做局部变量
        return 0;
}

 

• Do anonymous structure type

struct
{
    int a;
    char b;
    float c;
    //此处未完全声明变量，缺少了结构体标签
}b；

struct 
{
    int a;
    char b;
    float c;

}*ps;//结构体的指针变量，用来存储地址

• ps = & x;
  This way of writing is illegal, the compiler thinks these two different ways of writing are two different types.

2. Self-reference of structure

struct Node
{
    int data;
    struct Node*next;

};

int main()
{
    struct Node a = { 3, NULL };
    struct Node b = { 5, &a };
    printf("%d\n", b.data);
    printf("%p\n", b.next);
    system("pause");
    return 0;
}

• The following address is the address pointed to by b in the structure, namely the address of a.
• When the structure is self-referencing, it cannot be written as an anonymous structure type.

typedef struct
{
    int  data;
    Node* next;

}Node;

• The compilation error here is because Node is defined at the end, but it has been called inside the structure, which is illegal.

• The correct wording is as follows:

typedef struct  Node
{
    int  data;
    struct  Node* next;

}Node;

3. Definition and initialization of structure variables Initialization of simple structures

struct Point
{
    int x;
    int y;

};

int main()
{
    struct Point p2 = { 1, 2 };       //定义一个局部变量p2并且给其进行赋值
    printf("%d %d\n", p2.x, p2.y);
    system("pause");
    return 0;
}

 

• Initialization of structure nesting

struct Point
{
    int x;
    int y;
};
struct Node
{
    int data;
    struct Point p;
    struct Node* next;

};

int main()
{
    struct Node n1 = { 5, { 1, 2 }, NULL };
    struct Node n2 = { 8, { 3, 4 }, &n1 };
    printf("%d\n", n2.next->data);
    printf("%d %d\n", n2.next->p.x, n2.next->p.y);
    printf("%p\n", n2.next);

    system("pause");
    return 0;
}

You must use-> when the pointer points to the structure