C language, structure, structure size,

      1. Structure:

        Used to store multiple related variables of different data types to form an independent composite data type.

The declaration of the structure:

struct structure type name {

      datatype member 1;

      datatype member 2;

      datatype member 3;

………

} ; // Note the semicolon here

Declaration: Create a custom data type, this type is called <struct structure type name> è data type;

      struct student(){

      char name[32];

      int age;

      char sex;

      double score;

}；

struct student è customize a data type

Define structure variables:

      struct studet  structure variable name;

      struct studies stu;

initialization:

      struct student stu ={ “zhangsan”,18 ,’M’,88.8};

use:

      Structure variable name. Member name: -->  array name [subscript]

      stu.age -->18;

assignment:

      When assigning values ​​to the structure content, you can only assign values ​​one by one.

      But you can directly assign values ​​between structures of the same type.

Structure pointer:

      struct student *p;

      Use pointers to get data

      (*p).sex -->    'm' // basically not used

      p->sex --> ' m' // use this

/*===============================================
*   文件名称：struct_KT.c
*   创 建 者：WM
*   创建日期：2023年08月15日
*   描    述：结构体基础知识
================================================*/
#include <stdio.h>
#include<string.h>
#include <stdlib.h>
typedef struct student
{
    char name[32];
    int age;
    char sex;
    double score;
}stu,*pstu;

int main(int argc, char *argv[])
{
   // stu s1={"zhangsan",18,'m',88.8},s2;
    //s2=s1;
    // strcpy(s2.name,"lisi");
    // s2.age=19;
    // s2.sex='w';
    // s2.score=29.0;
    stu s3;
    scanf("%s",s3.name);
    scanf("%d",&s3.age);
    //scanf("%*c%c",&s3.sex);//方法1、去除脏字字符'\r'回车
    getchar(); //方法2、去除脏字字符'\r'回车,放在输入数据之前
    scanf("%c",&s3.sex);
    
    scanf("%lf",&s3.score);

    //结构体指针
    pstu p=&s3;
    printf("%s,%d,%c,%.2lf\n",s3.name,s3.age,s3.sex,s3.score);
    printf("%c\n",p->sex);

    pstu k=(struct student *)malloc(sizeof(stu));
    strcpy(k->name,"wangwu");
    puts(k->name);
    free(k);
    return 0;
} 

2. Structure size:

1. Aligned using the length of the largest data type in the structure members . A member will not be assigned to multiple grids.
2. Alignment operations start from top to bottom. It will only be placed in a position that is a multiple of the size of its own data type.
3. An array is equivalent to writing a bunch of variables of the corresponding type.

      

1111

1011

1000

so for 12

1111 1111

1111 1111

1111 1110

1100 0000

1111 1111

so for 40