Structures in C++

What is a structure?

A structure groups related pieces of data — of possibly different types — under one name. Instead of separate variables for a student's name, roll number and marks, you bundle them into one Student value.

Defining a struct

struct Student {
    string name;
    int roll;
    double marks;
};   // note the semicolon

This defines a new type called Student. The members are the variables inside it.

Creating and accessing

Create a variable of the struct type and reach its members with the dot operator:

#include <iostream>
using namespace std;
struct Student { string name; int roll; double marks; };

int main() {
    Student s;
    s.name = "Amit";
    s.roll = 12;
    s.marks = 88.5;
    cout << s.name << " (" << s.roll << "): " << s.marks << "\n";
    return 0;
}

You can also initialise at once: Student s = {"Amit", 12, 88.5};. With a pointer, use the arrow: p->name.

Array of structs

Storing many records is easy — make an array of the struct:

Student list[2] = {{"Amit", 1, 90}, {"Riya", 2, 95}};
for (int i = 0; i < 2; i++)
    cout << list[i].name << " " << list[i].marks << "\n";

Structs with functions

Pass a struct to a function — by const reference to avoid copying large ones:

void printStudent(const Student &s) {
    cout << s.name << ": " << s.marks << "\n";
}

struct vs class

The only language difference is default access. See classes and objects to go further with behaviour and encapsulation.

Common mistakes

• Forgetting the semicolon after the closing brace of a struct.
• Using . on a pointer instead of ->.
• Copying large structs by value when a const reference is better.
• Expecting struct members to be private — they are public by default.

Summary

• A struct groups related data of different types under one name.
• Access members with the dot operator (or -> via a pointer).
• Arrays of structs store many records of the same shape.
• Pass structs by const reference to functions to avoid copies.
• struct and class differ only in default access (public vs private).