Introduction to Programming in C

📘 Structures and Unions in C

In C, structures and unions are user-defined data types that allow grouping of different types of data under a single name. They help in organizing complex data, such as student records, product inventories, and more.

🔹 Structures in C

A structure is a collection of variables of different data types grouped together using the struct keyword.

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

To declare and use a structure variable:

struct Student s1;

s1.id = 1;
strcpy(s1.name, "Anjali");
s1.marks = 89.5;

printf("Name: %s, Marks: %.2f", s1.name, s1.marks);

📚 Real-Life Example (UdaanPath)

Let’s define and display details of a course listing on UdaanPath:

struct Course {
    char title[50];
    int duration; // in hours
    float price;
};

int main() {
    struct Course c1 = {"Intro to C Programming", 30, 299.99};

    printf("Course: %s\nDuration: %d hrs\nPrice: ₹%.2f\n", c1.title, c1.duration, c1.price);
    return 0;
}

📌 Array of Structures

You can store multiple student or product records using arrays of structures:

struct Student students[3];

for (int i = 0; i < 3; i++) {
    printf("Enter ID and marks for student %d: ", i+1);
    scanf("%d%f", &students[i].id, &students[i].marks);
}

🔄 Passing Structures to Functions

void display(struct Student s) {
    printf("%d %s %.2f", s.id, s.name, s.marks);
}

🔄 Pointers to Structures

struct Student *ptr = &s1;
printf("%s", ptr->name);

🧠 Nested Structures

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

struct Student {
    int id;
    struct Date dob;
};

🧩 Unions in C

A union is like a structure, but with a major difference: all members share the same memory space. This means only one member can hold a value at any time.

union Data {
    int i;
    float f;
    char str[20];
};

Useful when you need to use the same memory space for multiple purposes.

📊 Structure vs Union

📝 Practice Tasks

1. Create a structure to hold student information and print it.
2. Define a union and store int, float, and string — observe the results.
3. Write a program to input 5 products using a structure array and display them.
4. Pass structure to a function to print details.

✅ Summary

• Structures help group related variables of different types.
• Unions save memory by sharing the same space.
• Use structures for record-like data; use unions when only one variable is active at a time.

🚀 Coming Next

In the next chapter, we’ll learn how to pass arrays, structures, and pointers to functions for advanced control and abstraction.