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Structure

A structure in C is a user-defined data type that groups related variables of different data types into a single unit. It allows us to store multiple pieces of information together, making it useful for organizing complex data.

"In modern programming, databases are used to store structured data like employee or student details. However, in C, we use structures to group related information together, providing a way to handle such data within a program's memory."

Syntax:

struct structure_name   
{  
    data_type member1;  
    data_type member2;  
    .  
    .  
    data_type memeberN;  
};
Example 1:

A structure is defined using the struct keyword:

#include <stdio.h>
#include <string.h>
// Define a structure
struct Student {
    char name[50];
    int age;
    float marks;
};

int main() {
    // Declare a structure variable
    struct Student s1;
    strcpy(s1.name, "Alice");
    s1.age = 20;
    s1.marks = 90;

    // Accessing structure members
    printf("Name: %s\n", s1.name);
    printf("Age: %d\n", s1.age);
    printf("Marks: %.2f\n", s1.marks);

    return 0;
}

Output:

Name: Alice
Age: 20
Marks: 90.00

We use the dot (.) operator to store and access members like s1.name, s1.age, etc

Example 2: Storing values at one time
#include <stdio.h>

struct Student {
    char name[50];
    int age;
    float marks;
};

int main() {
    
    struct Student s1 = {"Alice", 20, 90};

    // Accessing structure members
    printf("Name: %s\n", s1.name);
    printf("Age: %d\n", s1.age);
    printf("Marks: %.2f\n", s1.marks);

    return 0;
}

Output:

Name: Alice
Age: 20
Marks: 90.00
Example 3: Storing data of multiple students.
#include <stdio.h>

// Define a structure
struct Student {
    char name[50];
    int age;
    float marks;
};

int main() {
    // Declare an array of structures
    struct Student students[2];

    // Input details for 2 students
    for (int i = 0; i < 2; i++) {
        printf("Enter details for Student %d:\n", i + 1);
        printf("Name: ");
        scanf("%s", students[i].name);
        printf("Age: ");
        scanf("%d", &students[i].age);
        printf("Marks: ");
        scanf("%f", &students[i].marks);
    }

    // Display student details
    printf("\nStudent Details:\n");
    for (int i = 0; i < 2; i++) {
        printf("Student %d - Name: %s, Age: %d, Marks: %.2f\n", i + 1, students[i].name, 
        students[i].age, students[i].marks);
    }

    return 0;
}

Output:

Enter details for Student 1:
Name: Alice
Age: 20
Marks: 85.5

Enter details for Student 2:
Name: Bob
Age: 22
Marks: 90.0

Student Details:
Student 1 - Name: Alice, Age: 20, Marks: 85.50
Student 2 - Name: Bob, Age: 22, Marks: 90.00