Structure

A structure is a user-defined data type that groups related variables of different types under one name.

struct Student {
    int id;
    double gpa;
    char grade;
};

// Creating variables
Student s1;
Student s2;
struct Student s3;   // C-style, works but unnecessary in C++
// C++ lets us drop the struct keyword when declaring variables.

Accessing members

We can access using . operator:

s1.id = 101;
s1.gpa = 8.6;
s1.grade = 'A';

Initialization

Aggregate initialization

Student s = {101, 8.6, 'A'};

Order matters.

Designated initializers (C++20)

Student s = {
.id = 101,
.gpa = 8.6,
.grade = 'A'
};

Readable. Safe. Less chance of swapping GPA with ID and ruining a career.

Struct with functions

struct Student {
    int id;
    double gpa;

    void print() {
        cout << id << " " << gpa << endl;
    }
};


Student s{101, 8.6};
s.print();

Structure and Functions

Passing by value (copy)

void print(Student s) {
    cout << s.id;
}

Copies everything. Fine for small structs, painful for big ones.

Passing by reference (recommended)

void print(Student& s) {
    cout << s.id;
}

Passing array of structures

Student sArr[10];

printAll(sArr);

Since, it's an array, it will be passed by reference only.

Array within Structure

struct Student {
    int id;
    double gpa;
    char grade;
    int subjectMarks[10];
};

When we pass this structure by value to a function, then the entire array of the structure will get copied.

Nested Structures

struct Address {
    string city;
    int pin;
};

struct Person {
    string name;
    Address addr;
};

We can access using . operator:

Person p;
p.addr.city = "Delhi";

Pointer to a Structure

Student s;
Student *p = &s;

(*p).id = 101;  // sets id of s
p->id = 101;    // sets id of s

p->x is just shorthand for (*p).x

Dynamic Structures

Student *p = new Student;
p->id = 101;
delete p;

Self Reference Structures

struct Employee {
    int eNumber;
    string name;
    Employee *next;
};

Employee e1;
e1.eNumber = 101;
e1.name = "Foo";
e1.next = NULL;

Employee e2;
e2.eNumber = 102;
e2.name = "Bar";
e2.next = &e1;

Structure vs Class

Feature	struct	class
Default access	`public`	`private`
Can have methods	Yes	Yes
Can have constructors	Yes	Yes
Can use inheritance	Yes	Yes

struct Example {
    private:
        int c;

    protected:
        int b;

    public:
        int a;
};

struct Base {
    int x;
};

struct Derived : Base {
    int y;
};

struct → public inheritance by default
class → private inheritance by default

Last modified: 08 February 2026