5-構造結合

1-構造体概念c

#include 
#include 
#include 

struct Student     //Student            
{
	int id;
	char name[32];
	char sex;
};
typedef struct Student stu;

int main()
{
	struct Student s1;      //       
	struct Student s2 = {2, "jack", 'm'};
	stu s3 = {3, "tim", 'm'};

	//s1 = {1, "jason", 'f'};

	s1.id = 1;
	strcpy(s1.name, "jason");
	s1.sex = 'f';

	printf("%d %s %c
", s1.id, s1.name, s1.sex);
	printf("%d %s %c
", s2.id, s2.name, s2.sex);

	stu *ps = (stu *)malloc(sizeof(stu) * 1);
	ps->id = 4;
	strcpy(ps->name, "lily");
	ps->sex = 'f';

	printf("%d %s %c
", ps->id, ps->name, ps->sex);

	//stu s4[5] = {0};     //     ，           
	stu s4[5] = {{5, "aaa", 'm'}, {6, "bbb", 'f'}};
	int i;
	for (i = 0; i < 2; i++)
	{
		printf("%d %s %c
", s4[i].id, s4[i].name, s4[i].sex);
	}

	stu *ps1[5] = {0};    //       

	return 0;
}


2-     .c

```#include <stdio.h>

//1、                  
//2、                    

struct T
{
	int x;
	char y;
};
struct Test
{
	char c[10];
	short a;
	float b;
	struct T t;
	char d;
};

int main()
{
	printf("%lu
", sizeof(struct Test));
	return 0;
}

3-   .c

```c
#include 

//           
union Test
{
	int a;
	int b;
	char c;
};

union Byte
{
	short val;
	char ch[sizeof(short)];
};

int main()
{
	union Test t1;
	t1.a = 100;
	printf("t1.b = %d
", t1.b);
	t1.a = 0x10101010;
	printf("t1.c = %x
", t1.c);

	union Byte b;
	b.val = 0x0102;
	if (b.ch[0] == 2 && b.ch[1] == 1)
	{
		printf("     
");
	}
	else if (b.ch[1] == 2 && b.ch[0] == 1)
	{
		printf("     
");
	}

	//          

	return 0;
}

4-列挙c

#include 

/*#define A 0
#define B 1
#define C 2
#define D 3*/

enum Num
{
	A,
	B,
	C = 1000,
	D
};

int main()
{
	printf("%d
", A);	
	printf("%d
", B);	
	printf("%d
", C);	
	printf("%d
", D);	

	return 0;
}