# 结构基本功能

结构声明由包含在花括号内的一系列声明组成，结构中定义的变量称为成员。

```c
#include <stdio.h>

struct point
{
    int x;
    int y;
};

int main(int argc, char const *argv[])
{
    return 0;
}
```

如果结构声明的后面不带变量名，则不需要为它分配存储空间，它仅仅描述了一个结构的模板或轮廓。如果结构声明后面带变量名，则可以通过该变量名直接使用结构功能。

```c
#include <stdio.h>

struct point
{
    int x;
    int y;
} p1, p2;

int main(int argc, char const *argv[])
{
    p1.x = 233;
    p1.y = 666;
    printf("x = %d, y = %d.\n", p1.x, p1.y);
    p2.x = 100;
    p2.y = 200;
    printf("x = %d, y = %d.\n", p2.x, p2.y);
    struct point p3;
    p3.x = 200;
    p3.y = 100;
    printf("x = %d, y = %d.\n", p3.x, p3.y);
    struct point p4 = {666, 233};
    printf("x = %d, y = %d.\n", p4.x, p4.y);
    return 0;
}
```

结构可以嵌套。

```c
#include <stdio.h>

struct point
{
    int x;
    int y;
};

struct info
{
    int width;
    int height;
};

struct rect
{
    struct point point;
    struct info info;
};

int main(int argc, char const *argv[])
{
    struct rect rect;
    rect.point.x = 100;
    rect.point.y = 100;
    rect.info.width = 300;
    rect.info.height = 200;
    printf("x: %d, y: %d.\n", rect.point.x, rect.point.y);
    printf("width: %d, height: %d.\n", rect.info.width, rect.info.height);
    return 0;
}
```