structural morphology

Form of structure

1. struct structure name
   {
   Structural member 1;
   Structural member 2;
   ...
   };
   For example: Book Structure

struct Book
{
    char title[128];
    char author[48];
    float price;
    unsigned int date;
    char publisher[40];
};

1. Defining structure type variables
   You can follow the variables when the structure is declared, which are global variables
   for example

struct Book
{
    char title[128];
    char author[48];
    float price;
    unsigned int date;
    char publisher[40];
}book;//boo is a global variable

It can also be defined in the main function

#include <stdio.h>

struct Book
{
    char title[128];
    char author[48];
    float price;
    unsigned int date;
    char publisher[40];
};

int main(void)
{
    struct Book book;//This is a local variable
    return 0;
}

1. Accessing structure variables
   To access structure members, we need to introduce a new operator, the dot (.) operator. For example, book.title refers to the title member of the book structure, which is a character array; book.price refers to the price member of the book structure, which is a floating-point variable

For example, books

#include <stdio.h>

struct Book
{
    char title[128];
    char author[48];
    float price;
    unsigned int date;
    char publisher[40];
}book;

int main(void)
{
    printf("Please enter the title of the book: ");
    scanf("%s", book.title);
    printf("Please enter author: ");
    scanf("%s", book.author);
    printf("Please enter the selling price: ");
    scanf("%f", &book.price);
    printf("Please enter publication date: ");
    scanf("%d", &book.date);
    printf("Please enter the publishing house: ");
    scanf("%s", book.publisher);

    printf("\n=======Data entry completed=====\n");

    printf("Title: %s\n", book.title);
    printf("author: %s\n", book.author);
    printf("price: %.2f\n", book.price);
    printf("Publication date: %d\n", book.date);
    printf("Press: %s\n", book.publisher);
    return 0;
}

Result output

Please input the title of the book: the old man and the sea
 Please enter Author: Hemingway
 Please enter the selling price: 20
 Please enter publication date: 20200113
 Please enter Publishing House: China University of mining and Technology Press

=======Data entry completed=====
Title: the old man and the sea
 By Hemingway
 Price: 20.00
 Publication date: 20200113
 Press: China University of mining and Technology Press

Initializing structure variables

Initialize a struct variable:

struct Book book = {
		"The old man and the sea",
		"Hemingway";
		20,
		20200113
		"China University of mining and Technology Press"
};

Be sure to take your seat

Initializes the specified member value of the structure

Struct initializer uses dot (.) operator and member name
For example: let the program only initialize the price member of Book:

struct Book book = {.price = 20};

You can also initialize without following the member order declared by the structure:

struct Book book = {
				.publisher = "China University of mining and Technology Press",
				.price = 20,
				.date = 20200113
};

Nested structure

Nesting example:

#include <stdio.h>

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

struct Book
{
    char title[128];
    char author[40];
    float price;
    struct Date date;//nesting
    char publisher[40];
}book = {
    "The old man and the sea",
    "Hemingway",
    20,
    {2020, 01, 13},
    "China University of mining and Technology Press"
};
int main(void)
{
    printf("Title: %s\n", book.title);
    printf("author: %s\n", book.author);
    printf("Price: %.2f\n", book.price);
    printf("date: %d-%d-%d\n", book.date.year, book.date.month,
           book.date.day);
    printf("Press: %s\n", book.publisher);

    return 0;
}

Output result

Title: the old man and the sea
 By Hemingway
 Price: 20.00
 Date: January 13, 2020
 Press: China University of mining and Technology Press

Structure array

The first method is defined when the structure is declared:

struct structure name
{
	Structural member 1;
	Structural member 2;
	...
}Array name [length];

The second method is to first declare a structure type, and then define a structure array with this type:

struct structure name
{
	Structural member 1;
	Structural member 2;
	...
};
struct structure name array name [length];

Initialize structure array

Example:

struct Book book[3] = {
	{"The old man and the sea", "Hemingway", 20, {2020, 01, 13}, "China University of mining and Technology Press"};
	{"The old man and the land", "Lu Ming Wei", 21, {2021, 01, 13}, "tsinghua university press "};
	{"Old man and empty", "Kong Ming Wei", 22, {2022, 01, 13}, "Peking University Press"};
};

Transfer structure variable

• Information can be transferred between structural variables through assignment numbers, provided that the types of variables are the same;

Example:

#include <stdio.h>

int main(void)
{
    struct Test
    {
        int x;
        int y;
    }t1, t2;

    t1.x = 3;
    t1.y = 4;

    t2 = t1;//Assignment number transfer
    printf("t2.x = %d, t2.y = %d", t2.x, t2.y);
    return 0;
}

Output result

t2.x = 3, t2.y = 4

Structure pointer

Example: book entry procedure

#include <stdio.h>

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

struct Book
{
    char title[128];
    char author[40];
    float price;
    struct Date date;
    char publisher[40];
};

struct Book getInput(struct Book book);
void printBook(struct Book book);

struct Book getInput(struct Book book)
{
    printf("Please enter the title of the book: ");
    scanf("%s", book.title);
    printf("Please enter author: ");
    scanf("%s", book.author);
    printf("Please enter the selling price: ");
    scanf("%f", &book.price);
    printf("Please enter publication date: ");
    scanf("%d-%d-%d", &book.date.year, &book.date.month, &book.date.day);
    printf("Please enter the publishing house: ");
    scanf("%s", book.publisher);

    return book;

};

void printBook(struct Book book)
{
    printf("Title: %s\n", book.title);
    printf("author: %s\n", book.author);
    printf("price: %.2f\n", book.price);
    printf("Publication date: %d-%d-%d\n", book.date.year,book.date.month,book.date.day);
    printf("Press: %s\n", book.publisher);
}

int main(void)
{
    struct Book b1, b2;
    printf("Please enter the information of the first book...\n");
    b1 = getInput(b1);
    putchar('\n');
    printf("Please enter the information of the second book...\n");
    b2 = getInput(b2);

    printf("\n\n Input completed,Print verification now...\n\n");
    printf("Print information for the first book..\n");
    printBook(b1);
    putchar('\n');
    printf("Print information for the second book..\n");
    printBook(b2);

    return 0;
}

Output result

Please enter the information of the first book
 Please input the title of the book: the old man and the sea
 Please enter Author: Hemingway
 Please enter the selling price: 20
 Please enter publication date: January 13, 2020
 Please enter: Tsinghua University Press

Please enter the information of the second book
 Please enter the title of the book: young people and the sea
 Please enter Author: Hemingway
 Please enter the selling price: 20
 Please enter publication date: January 13, 2020
 Please enter: Peking University Press


After input, start printing verification now

Print the first book
 Title: the old man and the sea
 By Hemingway
 Price: 20.00
 Publication date: January 13, 2020
 Press: Tsinghua University Press

Print information for the second book
 Title: young people and the sea
 By Hemingway
 Price: 20.00
 Publication date: January 13, 2020
 Press: Peking University Press

Now use structure pointer

Or the above example, slightly modified

#include <stdio.h>

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

struct Book
{
    char title[128];
    char author[40];
    float price;
    struct Date date;
    char publisher[40];
};

void getInput(struct Book *book);
void printBook(struct Book *book);

void getInput(struct Book *book)
{
    printf("Please enter the title of the book: ");
    scanf("%s", book->title);
    printf("Please enter author: ");
    scanf("%s", book->author);
    printf("Please enter the selling price: ");
    scanf("%f", &book->price);
    printf("Please enter publication date: ");
    scanf("%d-%d-%d", &book->date.year, &book->date.month, &book->date.day);
    printf("Please enter the publishing house: ");
    scanf("%s", book->publisher);
};

void printBook(struct Book *book)
{
    printf("Title: %s\n", book->title);
    printf("author: %s\n", book->author);
    printf("price: %.2f\n", book->price);
    printf("Publication date: %d-%d-%d\n", book->date.year,book->date.month,book->date.day);
    printf("Press: %s\n", book->publisher);
}

int main(void)
{
    struct Book b1, b2;
    printf("Please enter the information of the first book...\n");
    getInput(&b1);
    putchar('\n');
    printf("Please enter the information of the second book...\n");
    getInput(&b2);

    printf("\n\n Input completed,Print verification now...\n\n");
    printf("Print information for the first book..\n");
    printBook(&b1);
    putchar('\n');
    printf("Print information for the second book..\n");
    printBook(&b2);

    return 0;
}

Output result

Print the first book
 Title: the old man and the sea
 By Hemingway
 Price: 20.00
 Publication date: January 13, 2020
 Press: Tsinghua University Press

Print information for the second book
 Title: young people and the sea
 By Hemingway
 Price: 20.00
 Publication date: January 13, 2020
 Press: Peking University Press