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C++ Arrays


C++ Arrays

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value.

To declare an array, define the variable type, specify the name of the array followed by square brackets and specify the number of elements it should store:

string cars[4];

We have now declared a variable that holds an array of four strings. To insert values to it, we can use an array literal - place the values in a comma-separated list, inside curly braces:

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};

To create an array of three integers, you could write:

int myNum[3] = {10, 20, 30};

Access the Elements of an Array

You access an array element by referring to the index number.

This statement accesses the value of the first element in cars:

Example

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};
cout << cars[0];
// Outputs Volvo
Run example »

Note: Array indexes start with 0: [0] is the first element. [1] is the second element, etc.


Change an Array Element

To change the value of a specific element, refer to the index number:

Example

cars[0] = "Opel";

Example

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};
cars[0] = "Opel";
cout << cars[0];
// Now outputs Opel instead of Volvo
Run example »

Loop Through an Array

You can loop through the array elements with the for loop.

The following example outputs all elements in the cars array:

Example

string cars[4] = {"Volvo", "BMW", "Ford", "Mazda"};
for(int i = 0; i < 4; i++) {
  cout << cars[i] << "\n";
}
Run example »

Omit Array Size

You don't have to specify the size of the array. But if you don't, it will only be as big as the elements that are inserted into it:

string cars[] = {"Volvo", "BMW", "Ford"}; // size of array is always 3

This is completely fine. However, the problem arise if you want extra space for future elements. Then you have to overwrite the existing values:

string cars[] = {"Volvo", "BMW", "Ford"};
string cars[] = {"Volvo", "BMW", "Ford", "Mazda", "Tesla"};

If you specify the size however, the array will reserve the extra space:

string cars[5] = {"Volvo", "BMW", "Ford"}; // size of array is 5, even though it's only three elements inside it

Now you can add a fourth and fifth element without overwriting the others:

string cars[3] = {"Mazda"};
string cars[4] = {"Tesla"};
Run example »

Omit Elements on Declaration

It is also possible to declare an array without specifying the elements on declaration, and add them later:

string cars[5];
cars[0] = {"Volvo"};
cars[1] = {"BMW"};
...
Run example »

C++ Exercises

Test Yourself With Exercises

Exercise:

Create an array of type string called cars.

 [4] = {"Volvo", "BMW", "Ford", "Mazda"};

Start the Exercise