Advanced Coding & Software Engineering Program

Arrays in C++ – Complete Tutorial (Beginner to Advanced)

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Last Updated on: 10th Dec 2025 12:38:58 PM

An array in C++ is one of the most fundamental data structures used for storing multiple values of the same data type under a single variable name. Arrays make data management easier, faster, and more structured, especially when dealing with large sets of data like marks of students, prices of products, or elements in algorithms.

 

What is an Array in C++?

An array is a collection of elements of the same data type stored at contiguous memory locations, accessed using a single variable name with an index.

 

✔ Key Points

• Stores multiple data items of the same type

• Stored in continuous (contiguous) memory

• Index always starts from 0

• Fast access using index

• Useful for managing large datasets

 

Example

int numbers[5] = {10, 20, 30, 40, 50};

Why Do We Need Arrays?

Without arrays, storing 100 integers would require:

int a1, a2, a3, ... a100;  

 

This is unreadable and unmanageable.

With arrays:

int a[100];

 

Much easier for:

• loops

• operations

• searches

• sorting

• mathematical calculations

 

Memory Representation of an Array

Example:

int arr[4] = {5, 10, 15, 20};

 

Index	Value	Memory Address
0	5	1000
1	10	1004
2	15	1008
3	20	1012

 

(Assuming each int = 4 bytes)

📝 All memory locations are continuous, that’s why array operations are fast.

 

4. Types of Arrays in C++

C++ mainly supports:

1. One-Dimensional Array (1D)

2. Two-Dimensional Array (2D)

3. Multi-Dimensional Array

4. Character Arrays (Strings)

 

5. One-Dimensional Array (1D Array)

A one-dimensional array stores a list of values in a single row.

 

Syntax

data_type array_name[size];

 

Example

int marks[5];

 

6. Initialization of 1D Array

At Declaration Time

int arr[5] = {10, 20, 30, 40, 50};

 

Without Size

int arr[] = {1, 2, 3, 4};

 

7. Accessing Array Elements

Syntax

array_name[index];

 

index start from 0

cout << arr[0];  // First element

 

8. Input and Output of Array Using Loop

 

Example

#include <iostream>
using namespace std;

int main() {
    int arr[5];

    cout << "Enter 5 elements:\n";
    for (int i = 0; i < 5; i++) {
        cin >> arr[i];
    }

    cout << "Array elements are:\n";
    for (int i = 0; i < 5; i++) {
        cout << arr[i] << " ";
    }
    return 0;
}

 

 9. Common Operations on Arrays 

 

1. Traversing 

Accessing each element using loops.

 

2. Insertion 

Adding element at a specific index (manually shifting).

 

3. Deletion 

Removing element and shifting remaining elements.

 

4. Searching 

• Linear Search

• Binary Search (on sorted array)

 

5. Sorting 

• Bubble Sort

• Selection Sort

• Insertion Sort

 

10. Passing Array to Function

Arrays are passed to functions by reference (address).

 

Example

void display(int arr[], int n) {
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
}

int main() {
    int a[3] = {1, 2, 3};
    display(a, 3);
}

 

11. Two-Dimensional Array (2D Array)

A 2D array stores data in rows and columns (matrix form).

Syntax

data_type array_name[row][column];

 

Example

int marks[3][3];

 

12. Initialization of 2D Array

int arr[2][3] = {
    {1, 2, 3},
    {4, 5, 6}
};

 

13. Input & Output of 2D Array

#include <iostream>
using namespace std;

int main() {
    int a[2][2];

    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            cin >> a[i][j];
        }
    }

    cout << "Matrix:\n";
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            cout << a[i][j] << " ";
        }
        cout << endl;
    }
}

 

14. Multi-Dimensional Arrays

Arrays with more than two dimensions.

int arr[3][4][2];

 

Used rarely; mostly in:

• Graphics

• Scientific computing

• Tensor calculations

 

15. Character Arrays (Strings)

A character array stores characters ending with '\0' (null character).

char name[10] = "C++";

 

16. String Input Example

char name[20];
cin >> name;
cout << name;

 

or using  cin.getline(): 

cin.getline(name, 20);

 

17. Array Indexing Rules

1. Index starts from 0
2. Last index = size - 1
❌ Out-of-bound access causes runtime error

 

19. Advantages of Arrays

1. Easy data management
2. Fast access
3. Useful for sorting/searching
4. Works well with loops

 

20. Limitations of Arrays

1. Fixed size
2. Cannot grow dynamically
3. Insertion and deletion costly
4. Homogeneous data only

 

 Note : These limitations lead to Vectors, Linked Lists, and STL containers. 

 

21. Array vs Variables

Feature	Variable	Array
Stores	Single value	Multiple values
Access	Direct	Indexed
Memory	Single	Contiguous block

 

22. Common Mistakes

1. Accessing out-of-bound index
2. Using wrong loop condition
3. Forgetting array size
4. Confusing index and size

 

23. Interview-Important Programs

1. Find largest & smallest element
2. Reverse an array
3. Sum and average
4. Sorting array
5. Searching element
6. Matrix addition & multiplication

 

24. Real-World Applications

• Student management systems

• Inventory systems

• Data analysis

• Game development

• Image processing

 

Conclusion

Arrays in C++ are a powerful structure for storing and processing collections of data. They are fast, easy to use, and essential for loops, algorithms, data structures, and real-world applications. Mastering arrays is the first step to mastering data structures in C++.

 

✅ Strong array knowledge = strong programming base

 

Keep practicing — you're doing amazing!

Happy Coding!    

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