[C++知识库]C语言第28天，结构体进阶，嵌套初始化，内存对齐，传参

结构体全局变量，局部变量

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

struct Stu {
	char name[20];
	char tele[12];
	char sex[10];
	int age;
}s4, s5, s6;//s4,s5,s6 - 全局变量

struct Stu s3;//全局变量

int main() {
	struct Stu s1;
	struct Stu s2;//s1,s2 - 局部变量
	return 0;
}

结构体嵌套初始化

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

struct T
{
	double weight;
	short age;
};

struct S {
	char c;
	struct T st;
	int a;
	double d;
	char arr[20];
};

int main() {
	struct S s = { 'c',{55.6,30},100,3.14,"hello world" };
	printf("%c %d %lf %s\n", s.c, s.a, s.d, s.arr);
	printf("%lf %d\n", s.st.weight,s.st.age);
	return 0;
}

c 100 3.140000 hello world
55.600000 30

结构体内存对齐

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

//结构体内存对齐

struct S1 {
	char c1;//1
	char c2;//1
	//2
	int a;//4
};

struct S2 {
	char c1;//1
	//3
	int a;//4
	char c2;//1
	//3
};

struct S3 {
	double d;//8
	char c;//1
	int a;//4
	//3
};

struct S4 {
	char c1;
	struct S3 s3;
	double d;
};
int main() {
	struct S1 s1 = { 0 };
	printf("%d\n", sizeof(s1));//8
	struct S2 s2 = { 0 };
	printf("%d\n", sizeof(s2));//12
	struct S3 s3 = { 0 };
	printf("%d\n", sizeof(s3));//16
	struct S4 s4 = { 0 };
	printf("%d\n", sizeof(s4));//32
}

8
12
16
32

结构体传参

#define _CRT_SECURE_NO_WARNINGS

#include<stdio.h>

//结构体传参

struct S {
	int a;
	char c;
	double d;
};

void Init(struct S* ps) {
	ps->a = 100;
	ps->c = 'w';
	ps->d = 3.14;
}

//传值
void Print1(struct S tmp) {
	printf("%d %c %lf\n", tmp.a, tmp.c, tmp.d);
}
//传址
void Print2(struct S* ps) {
	printf("%d %c %lf\n", ps->a, ps->c, ps->d);
}

int main() {
	struct S s = { 0 };
	Init(&s);
	Print1(s);//100 w 3.140000
	Print2(&s);//100 w 3.140000
}

100 w 3.140000
100 w 3.140000