Module 11: Structures in C++

A structure (struct) is a user-defined data type that groups multiple variables of different data types under a single name. Structures are useful for representing real-world entities such as students, employees, books, and products.

For example, instead of storing a student's name, age, and marks in separate variables, you can store them together in a structure.

1. Structure Declaration

A structure is declared using the struct keyword.

Syntax

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1struct StructureName
2{
3    dataType member1;
4    dataType member2;
5};

Example

cppCopy
1#include <iostream>
2#include <string>
3
4using namespace std;
5
6struct Student
7{
8    string name;
9    int age;
10};
11
12int main()
13{
14    Student s1;
15
16    s1.name = "Ankit";
17    s1.age = 22;
18
19    cout << "Name: " << s1.name << endl;
20    cout << "Age: " << s1.age << endl;
21
22    return 0;
23}

Output

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1Name: Ankit
2Age: 22

2. Nested Structure

A nested structure is a structure that contains another structure as one of its members.

Example

cppCopy
1#include <iostream>
2#include <string>
3
4using namespace std;
5
6struct Address
7{
8    string city;
9    string state;
10};
11
12struct Student
13{
14    string name;
15    int age;
16    Address address;
17};
18
19int main()
20{
21    Student s;
22
23    s.name = "Ankit";
24    s.age = 22;
25    s.address.city = "Lucknow";
26    s.address.state = "Uttar Pradesh";
27
28    cout << s.name << endl;
29    cout << s.address.city << endl;
30
31    return 0;
32}

Output

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1Ankit
2Lucknow

3. Array of Structures

An array of structures stores multiple records of the same structure type.

Example

cppCopy
1#include <iostream>
2#include <string>
3
4using namespace std;
5
6struct Student
7{
8    string name;
9    int age;
10};
11
12int main()
13{
14    Student students[2] =
15    {
16        {"Ankit", 22},
17        {"Rahul", 21}
18    };
19
20    for (int i = 0; i < 2; i++)
21    {
22        cout << students[i].name << " ";
23        cout << students[i].age << endl;
24    }
25
26    return 0;
27}

Output

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1Ankit 22
2Rahul 21

4. Pointer to Structure

A pointer can store the address of a structure. The arrow operator (->) is used to access members through a pointer.

Example

cppCopy
1#include <iostream>
2#include <string>
3
4using namespace std;
5
6struct Student
7{
8    string name;
9    int age;
10};
11
12int main()
13{
14    Student s = {"Ankit", 22};
15
16    Student* ptr = &s;
17
18    cout << ptr->name << endl;
19    cout << ptr->age << endl;
20
21    return 0;
22}

Output

textCopy
1Ankit
222

Note: ptr->name is equivalent to (*ptr).name.

Structure vs Class

Best Practices

• Use meaningful structure names.
• Group related data together.
• Use arrays of structures for multiple records.
• Pass structures by const reference when possible to avoid unnecessary copying.
• Use structure pointers for efficient access to large structures.

Practice Problems

1. Create a structure for an Employee.
2. Store information for five students using an array of structures.
3. Create a nested structure for a Customer and Address.
4. Access structure members using a pointer.
5. Write a program to calculate the average marks of students stored in a structure array.

Interview Questions

1. What is a structure in C++?
2. What is the difference between a structure and a class?
3. What is a nested structure?
4. How do you create an array of structures?
5. What is a pointer to a structure?
6. What does the -> operator do?
7. When should you use a structure instead of a class?

Summary

In this module, you learned:

• What structures are and why they are useful.
• How to declare and use structures.
• How nested structures organize related data.
• How arrays of structures store multiple records.
• How pointers access structure members using the -> operator.
• The differences between structures and classes.

Next Module: Module 12: Enumerations and Type Aliases — enum, enum class, typedef, using, scoped enumerations, and practical examples.