Structures and Union in C

 Structures and Unions

Introduction: Structures and unions are composite data types in C that allow the grouping of multiple variables of different data types under a single name. They provide a way to represent complex data structures in a program, making it easier to organize and manipulate data.

Definition:

1. Structure:

   • A structure is a collection of variables (of different data types) grouped together under a single name.
   • Each variable within a structure is called a member or field.
   • Structures enable the creation of custom data types to represent real-world entities.
   • They are defined using the struct keyword.

2. Union:

• A union is similar to a structure in that it also groups variables of different data types under a single name.
• However, unlike structures, unions allocate memory that is only as large as the largest member.
• This means that only one member of the union can be accessed at a time.
• Unions are useful when memory conservation is a concern, and only one member needs to be accessed at a time.
• They are defined using the union keyword.
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Programming Code in C Explaining the Working of Both:

1. Structure Example:

c
#include <stdio.h>

// Defining a structure to represent a student 
struct Student
 {
    int rollNumber; 
char name[50]; 
float marks;
}; 
int main()
 {
    // Creating an instance of the structure 
struct Student student1;

    // Assigning values to the members of the structure
    student1.rollNumber = 101; 
strcpy(student1.name, "John"); 
 student1.marks = 85.5;

    // Accessing and printing the values of structure members
    printf("Student Details:\n"); 
printf("Roll Number: %d\n", student1.rollNumber); 
printf("Name: %s\n", student1.name); 
printf("Marks: %.2f\n", student1.marks);
return 0;
}

Explanation:

• In this example, a structure named Student is defined to represent information about a student, including roll number, name, and marks.
• An instance of the structure named student1 is created in the main() function.
• Values are assigned to the members of the structure using dot (.) operator.
• Finally, the values of the structure members are accessed and printed to the console.

2. Union Example:

c
#include <stdio.h>

// Defining a union to represent a book 
union Book 
{
    char title[50]; 
float price;
}; 
int main()
 {
    // Creating an instance of the union 
union Book book1;

    // Assigning values to the members of the union
    strcpy(book1.title, "Introduction to C Programming"); 
printf("Book Title: %s\n", book1.title); 
 book1.price = 29.99; 
printf("Book Price: %.2f\n", book1.price); 
return 0;
}

Explanation:

• In this example, a union named Book is defined to represent information about a book, including title and price.
• An instance of the union named book1 is created in the main() function.
• Initially, the title of the book is assigned to the title member of the union.
• Later, the price of the book is assigned to the price member of the union.
• When the price is assigned, the previous value of the title member is overwritten.
• Finally, both the title and price of the book are printed to the console.

Conclusion: Structures and unions are powerful features of C programming that enable the creation of custom data types to represent complex entities. By grouping variables of different data types under a single name, structures and unions enhance code organization, readability, and maintainability. Understanding how to define, declare, and use structures and unions is essential for developing efficient and scalable C programs.