Defining and Using Structures

Structures (struct) allow us to group related variables under a single name.

In this lesson, you will learn:

• How to define and use structures.
• How to access structure members.
• How to pass structures to functions.

What is a Structure?

A structure is a user-defined data type that groups different variables.

Example structure definition:

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

Here, a Person structure stores name, age, and height.

Declaring and Initializing a Structure

After defining a structure, we can declare and initialize it:

struct Person p1 = {"Alice", 25, 5.7};

We can also assign values later:

p1.age = 30;

Accessing Structure Members

Structure members are accessed using the dot (.) operator.

Example:

printf("Name: %s\n", p1.name);

This prints the name stored in the structure.

Example: Using Structures

This program demonstrates defining, initializing, and accessing a structure.

#include <stdio.h>

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

int main() {
    struct Person p1 = {"Alice", 25, 5.7};
    printf("Name: %s\n", p1.name);
    printf("Age: %d\n", p1.age);
    printf("Height: %.1f\n", p1.height);
    return 0;
}

Pointers to Structures

We can use pointers to structures for efficient memory management.

Example:

struct Person *ptr = &p1;

Members are accessed using the arrow (->) operator:

printf("%s", ptr->name);

Example: Structure Pointers

This program demonstrates accessing structure members using pointers.

#include <stdio.h>

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

int main() {
    struct Person p1 = {"Bob", 30};
    struct Person *ptr = &p1;
    printf("Name: %s\n", ptr->name);
    printf("Age: %d\n", ptr->age);
    return 0;
}

Passing Structures to Functions

Structures can be passed to functions by value or reference.

Example (pass by reference):

void update(struct Person *p) { p->age += 1; }

Passing by reference avoids copying large structures.

Summary

In this lesson, you learned:

• How to define and use structures.
• How to access structure members.
• How to use pointers with structures.

Next, we will explore unions and memory efficiency in C!