C++ Structs Explained: How to Use struct with Examples

Before you learn classes, you should understand structs. A struct lets you group related data together into a single named type — and in C++, structs are more powerful than you might expect.

This article covers how structs work, how to use them, and how they relate to classes.

What Is a Struct?

A struct (short for structure) is a user-defined type that bundles multiple variables together. Instead of managing separate variables for a student’s name, age, and grade, you can group them into one Student struct.

struct Student {
    string name;
    int age;
    double grade;
};

This defines a new type called Student. You can then create variables of that type:

Student s1;
s1.name  = "Alice";
s1.age   = 20;
s1.grade = 92.5;

Declaring and Initialising Structs

Basic Declaration

#include <iostream>
#include <string>
using namespace std;

struct Student {
    string name;
    int age;
    double grade;
};

int main() {
    Student s1;
    s1.name  = "Alice";
    s1.age   = 20;
    s1.grade = 92.5;

    cout << s1.name << " aged " << s1.age
         << " with grade " << s1.grade << endl;

    return 0;
}

Output:

Alice aged 20 with grade 92.5

Aggregate Initialisation (Cleaner Syntax)

You can initialise all members at once using braces, in the order they are declared:

Student s1 = {"Alice", 20, 92.5};
Student s2 = {"Bob", 22, 85.0};

Or with designated initialisers (C++20):

Student s1 = {.name = "Alice", .age = 20, .grade = 92.5};

Accessing Members with the Dot Operator

Use the . operator to access and modify struct members:

Student s;
s.name = "Charlie";
s.age = 19;

cout << s.name << endl;  // Charlie
s.age++;                 // Increment age
cout << s.age << endl;   // 20

Structs as Function Parameters

Pass structs to functions the same way as any other type. Use const reference to avoid copying:

void printStudent(const Student& s) {
    cout << "Name: " << s.name << endl;
    cout << "Age:  " << s.age  << endl;
    cout << "Grade:" << s.grade << endl;
}

int main() {
    Student s1 = {"Alice", 20, 92.5};
    printStudent(s1);
    return 0;
}

Arrays of Structs

You can create arrays (or vectors) of structs to store multiple records:

#include <iostream>
#include <vector>
#include <string>
using namespace std;

struct Student {
    string name;
    int age;
    double grade;
};

int main() {
    vector<Student> students = {
        {"Alice",   20, 92.5},
        {"Bob",     22, 85.0},
        {"Charlie", 19, 78.3}
    };

    for (const Student& s : students) {
        cout << s.name << ": " << s.grade << endl;
    }

    return 0;
}

Output:

Alice: 92.5
Bob: 85
Charlie: 78.3

Structs with Member Functions

In C++, structs can have member functions — unlike in C:

struct Rectangle {
    double width;
    double height;

    double area() {
        return width * height;
    }

    double perimeter() {
        return 2 * (width + height);
    }
};

int main() {
    Rectangle r = {5.0, 3.0};
    cout << "Area: "      << r.area()      << endl; // 15
    cout << "Perimeter: " << r.perimeter() << endl; // 16
    return 0;
}

Nested Structs

Structs can contain other structs:

struct Address {
    string street;
    string city;
    string country;
};

struct Person {
    string name;
    int age;
    Address address;  // Nested struct
};

int main() {
    Person p;
    p.name            = "Alice";
    p.age             = 30;
    p.address.street  = "123 Main St";
    p.address.city    = "Sydney";
    p.address.country = "Australia";

    cout << p.name << " lives in " << p.address.city << endl;
    return 0;
}

Pointer to a Struct — The Arrow Operator

When you have a pointer to a struct, use -> instead of . to access members:

Student s = {"Alice", 20, 92.5};
Student* ptr = &s;

// These are equivalent:
cout << ptr->name  << endl;  // Arrow operator (cleaner)
cout << (*ptr).name << endl; // Dereference then dot

The arrow operator -> is shorthand for dereference + dot. You will see it constantly when working with dynamically allocated objects or linked lists.

Struct vs Class: What Is the Difference?

In practice, use struct when you are grouping plain data (like a Point, a Colour, or a Config), and use class when you have behaviour, invariants, and encapsulation to protect.

Practical Example: Simple Contact Book

#include <iostream>
#include <vector>
#include <string>
using namespace std;

struct Contact {
    string name;
    string phone;
    string email;
};

void printContact(const Contact& c) {
    cout << "Name:  " << c.name  << endl;
    cout << "Phone: " << c.phone << endl;
    cout << "Email: " << c.email << endl;
    cout << "---" << endl;
}

int main() {
    vector<Contact> contacts = {
        {"Alice Smith",  "0400-111-222", "alice@email.com"},
        {"Bob Jones",    "0400-333-444", "bob@email.com"},
        {"Charlie Brown","0400-555-666", "charlie@email.com"}
    };

    for (const Contact& c : contacts) {
        printContact(c);
    }

    return 0;
}

Related Articles

• Object-Oriented Programming in C++: Classes & Objects — the natural step up from structs, introducing encapsulation and access control.
• C++ Variables and Data Types — the building blocks you group together inside structs.
• C++ Vector Tutorial: Complete Guide to std::vector — use vectors to store collections of structs.
• How to Use Pointers in C++ — understand the arrow operator and pointer-to-struct patterns.
• C++ Pass by Value, Reference & Pointer: Complete Guide — learn the best way to pass structs to functions.
• C++ Cheat Sheet: Quick Reference for Syntax, STL, and OOP — quick reference for struct syntax alongside classes and OOP.