C language structure - learning 27

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Type of structure

• User created by Different types of data Composed of a combined data structure , It's called Structure .
• The general form of declaring a struct type is :
  • struct Structure name { Member list };

explain :

• 1. Many types of structures can be designed
• for example ：
  • struct Teacher
  • struct Worker
  • struct Date And so on , Each contains different members
• 2. Members can belong to another structure type
• for example ：

struct Date
    { int month; int day; int year; };

struct Student{
      int num;
      char name[20];
      char sex;
      int age;
      struct Date birthday;
};

Structure type variable

• 1. First Declare the struct type , Again Define variables of this type .
  • for example ：

//  Declare the struct type 
struct Student{ 
      int num;
      char name[20];
      char sex;
      int age;
};

//  Define variables of this type 
//  Structure type name    Structure variable name 
struct Student student1,student2;

• 2. Define variables while declaring types
  • for example ：

struct Student{
      int num;
      char name[20];
      char sex;
      int age;
}student1,student2;

• 3. Define struct type variables directly without specifying type names
  • The general form is :
    • struct{ List of members } Variable name table column ; Specified a unknown The type of structure .
• for example ：

struct 
{
      int num;
      char name[20];
      char sex;
      int age;
}student1,student2;

explain ：

• 1. Type of structure And Structural variable It's a different concept , Don't mix up .
  • Only variables can be assigned 、 Access or operation , Instead of assigning a value to a type 、 Access or operation .
  • At compile time , Yes The type is unallocated space Of , only Allocate space to variables . Memory allocated to structural variables Storage space yes The total storage space occupied by each member variable .
• 2. In structure type The member name can be the same as the variable name in the program , but They don't represent the same object .
• 3. Structure variables can be initialized and assigned at the time of definition . When initializing a structure variable , The initial values assigned are placed in a pair of curly brackets in sequence .
  • for example ：

struct Student{
      int num;
      char name[20];
      char sex;
      int age;
}student1={2022160123,"Zhang san"," male ",24},student2;

A reference to a member of a structure variable

• Structure variables are construction type variables , There are two objects that can access operations .
  • 1. Structure Members of variables ;
  • 2. Structure Variable itself , Represents the All data members .
• Refer to members of structural variables
  • Access form of structure variable members :
    • Structure variable name . Member name
  • for example ：
    • student1.name
  • Order number “.” be called member operator , yes Binary operator , Priority is first stage , Associativity is from left to right .
• Members of structure variables can participate in various operations like ordinary variables
  • for example ：
    • student2.num = student1.num++;

explain ：

• 1. If the member itself is a structure type , You need several member operators , Step by step Only the lowest level members can use .
  • for example ：
    • student2.birthday.day =18;
• 2. You can refer to the address of the variable member of the structure , here “&” Put it on The structure variable name is preceded by .
  • for example ：
    • scanf( "%d" ,&student2.num);
• 3.“&” and “.” At the same time , Operator “.” High priority
  • for example ：
    • expression student1.num++ Equivalent to (student1.num)++.
• 4. Same structure type The structure variable of can Direct mutual assignment .
  • for example ：
    • Put the variable student1 All member values of are assigned to variables one by one student2 All member values of
    • student2 = student1;
• 5. Structure variables are different from basic type variables , Don't use it directly for arithmetic 、 Operations such as relation and logic , You can only compare members one by one .
• 6. You cannot input structural variables as a whole / Output , You can only input or output one by one for each member .
• 7. A piece of contiguous memory occupied by structural variables The first address Call it The address of the structure variable , The number of memory units occupied by each member The first address be called Member's address , Both addresses can refer to .

Example

Put a student's information ( Including student ID 、 full name 、 Gender 、 Age ) Put it in a structure variable , Then output the student's information .

#include <stdio.h>

void main() {
    struct Student {
        long int num;
        char name[20];
        char sex;
        int age;
    }std = { 10001,"Zhang san",'M',20 };
    printf(" Student number ：NO.%ld\n full name ：%s\n Gender ：%c\n Age ：%d\n",
        std.num,std.name,std.sex,std.age);
}

Enter the student number of two students 、 Name and score , Output the student number of students with higher grades 、 Name and score

#include <stdio.h>

void main() {
    struct Student {
        long int num;
        char name[20];
        float score;
    }std1,std2;

    printf(" Please enter student information ：\n");

        //  For array input ,scanf_s To define the buffer size , and name Don't add... In front &,name Itself is the address 

    scanf_s("%d%s%f", &std1.num, std1.name,21, &std1.score);
    scanf_s("%d%s%f", &std2.num, std2.name,21, &std2.score);

    if (std1.score > std2.score) {
        printf(" Student number ：NO.%ld\n full name ：%s\n achievement ：%.2f\n",
            std1.num, std1.name, std1.score);
    }
    else if (std1.score < std2.score) {
        printf(" Student number ：NO.%ld\n full name ：%s\n achievement ：%.2f\n",
            std2.num, std2.name, std2.score);
    }
    else {
        printf(" Student number ：NO.%ld\n full name ：%s\n achievement ：%.2f\n",
            std1.num, std1.name, std1.score);
        printf(" Student number ：NO.%ld\n full name ：%s\n achievement ：%.2f\n",
            std2.num, std2.name, std2.score);
    }
    
}