What is Structure in C ?

In C, a structure is a user-defined data type that allows you to combine different types of variables under a single name. It is used to group related data items together. Structures provide a convenient way to represent complex data structures such as records, objects, or entities.

To declare a structure in C, you use the struct keyword followed by the structure name and a set of braces {} that contain the members of the structure. Each member is declared with its data type and name.

Here’s an example of a simple structure declaration in C:

struct Person {
    char name[50];
    int age;
    float height;
};

In the above example, we declared a structure named Person with three members: name of type character array, age of type integer, and height of type float.

To access the members of a structure, you use the dot . operator. Here’s an example:

struct Person john;
strcpy(john.name, "John Doe");
john.age = 25;
john.height = 1.75;

In the above code, we declared a structure variable named john of type Person. We can access the members of the structure using the dot operator and assign values to them.

Types of Structures in C:

1. Structure without a tag:

struct {
    int x;
    int y;
} point;

2. Structure with a tag:

struct Point {
    int x;
    int y;
};
struct Point point;

3. Structure with typedef:

typedef struct {
    int x;
    int y;
} Point;
Point point;

Examples of Structure in C

1. Person Information

#include <stdio.h>

struct Person {
    char name[50];
    int age;
};

int main() {
    struct Person john;
    strcpy(john.name, "John Doe");
    john.age = 25;
    
    printf("Name: %s\n", john.name);
    printf("Age: %d\n", john.age);
    
    return 0;
}

Output:

Name: John Doe
Age: 25

Explanation:

In above example, we define a simple structure named Person with two members: name (a character array to store a person’s name) and age (an integer to store the person’s age). In the main function, we create an instance of this structure named john. We then use strcpy to copy the name “John Doe” into john.name and set john.age to 25. Finally, we print out the values of john.name and john.age.

2. Rectangle Area Calculation

#include <stdio.h>

struct Rectangle {
    int width;
    int height;
};

int area(struct Rectangle rect) {
    return rect.width * rect.height;
}

int main() {
    struct Rectangle rect;
    rect.width = 5;
    rect.height = 10;
    
    int rectArea = area(rect);
    
    printf("Rectangle Area: %d\n", rectArea);
    
    return 0;
}

Output:

Rectangle Area: 50

Explanation:

In above example, we define a structure named Rectangle with two members: width and height, both of type integer. We then declare a function area that takes a Rectangle structure as a parameter and calculates the area of the rectangle. In the main function, we create an instance of the Rectangle structure named rect, set its width and height, and then calculate and print its area.

3. Employee Database Management

#include <stdio.h>

struct Employee {
    char name[50];
    int age;
    float salary;
};

void displayEmployee(struct Employee emp) {
    printf("Name: %s\n", emp.name);
    printf("Age: %d\n", emp.age);
    printf("Salary: %.2f\n", emp.salary);
}

int main() {
    struct Employee employees[3];
    
    for (int i = 0; i < 3; i++) {
        printf("Enter details of Employee %d:\n", i + 1);
        printf("Name: ");
        scanf("%s", employees[i].name);
        printf("Age: ");
        scanf("%d", &employees[i].age);
        printf("Salary: ");
        scanf("%f", &employees[i].salary);
    }
    
    printf("\nEmployee Details:\n");
    for (int i = 0; i < 3; i++) {
        displayEmployee(employees[i]);
        printf("--------------------\n");
    }
    
    return 0;
}

Output:

Enter details of Employee 1:
Name: John
Age: 30
Salary: 50000

Enter details of Employee 2:
Name: Alice
Age: 28
Salary: 45000

Enter details of Employee 3:
Name: Bob
Age: 35
Salary: 60000

Employee Details:
Name: John
Age: 30
Salary: 50000.00
--------------------
Name: Alice
Age: 28
Salary: 45000.00
--------------------
Name: Bob
Age: 35
Salary: 60000.00
--------------------

Explanation:

In above example, we define a structure named Employee with three members: name (a character array to store the employee’s name), age (an integer to store the employee’s age), and salary (a float to store the employee’s salary). We also define a function displayEmployee that takes an Employee structure as a parameter and displays its details.

In the main function, we create an array of Employee structures named employees to store information about three employees. We use a loop to input the details of each employee (name, age, and salary) and then display their details using the displayEmployee function.

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