C++ Array Size

In C++, you can get the size of an array in several ways. The most common approach depends on whether you’re using a static array (i.e., an array with a fixed size).

Example:


#include <iostream>
using namespace std;

int main() {
    int arr[] = {10, 20, 30, 40, 50};
    
    // Get the size of the array
    int size = sizeof(arr) / sizeof(arr[0]);

    cout << "The size of the array is: " << size << endl;

    return 0;
}

Explanation:

  1. sizeof(arr) gives the total size of the array in bytes, It has 5 element and every integer element has 4 bytes so total bytes = 5*4= 20.
  2. sizeof(arr[0]) gives the size of a single element of the array.
  3. Dividing sizeof(arr) by sizeof(arr[0]) gives the total number of elements in the array.

Output:

The size of the array is: 5

Use Array Size in for loop


#include <iostream>
using namespace std;

int main() {
    int arr[] = {10, 20, 30, 40, 50};
    
    for(int i=0; i < sizeof(arr) / sizeof(arr[0]); i++) {
        
        cout << "Array element: " << arr[i] << endl;
        
    }
    return 0;
}

Explanation:

  1. Array Declaration: int arr[] = {10, 20, 30, 40, 50}; creates an array with 5 elements.
  2. Array Size: sizeof(arr) / sizeof(arr[0]) calculates the number of elements in the array instead of direct pass value 5.
  3. Looping: A for loop is used to iterate through the array and print each element

Output:

Array element: 10
Array element: 20
Array element: 30
Array element: 40
Array element: 50

C++ Array Size – Questions and Answers

Q 1: How do you find the size of an array in C++?

Ans: Using sizeof(arr) / sizeof(arr[0]).

Q 2: What happens if you access an index outside array size?

Ans: It causes undefined behavior.

Q 3: Can array size be zero?

Ans: No, C++ does not allow zero-sized arrays.

Q 4: Is array size decided at runtime?

Ans: No, standard arrays require compile-time constant size.

Q 5: Which alternative supports dynamic size?

Ans: vector from STL.

C++ Array Size – Objective Questions (MCQs)

Q1. Which operator is used to find the size of an array in C++?





Q2. What does sizeof(arr) return for the following code?

int arr[5];
cout << sizeof(arr);





Q3. How can you find the total number of elements in an array?





Q4. What will be the output?

int arr[] = {1, 2, 3, 4};
cout << sizeof(arr) / sizeof(arr[0]);





Q5. If float arr[10]; is declared, and size of float is 4 bytes, what will sizeof(arr) return?





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