Introduction to Arrays: C++ Crash Course (Free Tutorial)

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Arrays are lists of objects. For instance, there are integer arrays, which will give you lists of integers. String arrays will give you lists of strings. Sometimes, you can even have a mixture of the two.

Let’s start by looking at integer arrays. If you feel like testing out some code in real time, go on over to This site allows you to code in the main window, and test out your code instantly. Declare an integer named my_array.

int my_array;

In, your main coding screen should look like this:

//g++ 4.9.3

#include <iostream>

int my_array;

int main ()
std:cout << "Hello, world!\n";

Right now, my_array is still an integer. To make it into an integer array, add square brackets to the end of the array name.

This symbolizes that it’s an array of integers rather than just one variable of type integer.

int my_array[];

Now let’s give our array a size. Let’s say there are 3 elements in this array.

int my_array[3];

Yay! We have just created an array of 3 integers. As we haven’t specified which 3 integers will be in this array, the C++ compiler will populate the array with 3 zeros. However, zeros are boring, so let’s add some values ourselves. Open up the curly brackets to enter in values 1, 2, and 3.

int my_array[3]= {1, 2, 3};

We have just populated our array with the integers 1, 2, and 3. Note: element counts in arrays start at zero. Thus, in this array, Element Zero is 1, Element One is 2, and Element Two is 3.

In order to test your code, access one element of the array and print it out. To access the first element, call my_array and specify the first element. Replace "Hello, world!\n" with my_array[0];.

Scroll down to the bottom and press “Run It”. You will see the number “1” appear at the bottom of the screen.

To check that things are working properly throughout the array, check the last element (Element Two). Replace my_array[0]; with my_array[2];.

If you run the code, you will see the number “3” appear at the bottom of the screen.


Now let’s take a look at string arrays. Beneath your integer array, start with a standard string, and call it string_array. To make it into a string array, add square brackets to the end of the array name.

std::string string_array[];

Populate the array with two strings named "mammoth" and "interactive".

std::string string_array[] = {"mammoth", "interactive"};

Note that it’s not necessary to specify the size of the array within the square brackets. If you want to, you can put a 2 between the square brackets.

Instead of my_array, we want to access string_array. Let’s access the very first element in that array:

std:: cout << string_array[0];

By running the code, you will see “mammoth” appear at the bottom of your screen, which is the first element of our string array.

To check that things are working properly throughout the array, check the last element. Replace string_array[0]; with string_array[1];.

If you run the code, you should see “interactive” appear at the bottom of your screen.


Now let’s learn how to modify a single element in an array. Going back to the integer array example, let’s say we want to replace 2 with 5. In the main function, add my_array[1] = 5.

Also, we’ll be accessing my_array this time, so change string_array to my_array. As well, because we’ll be accessing Element One, you can leave the [1] where it is.

Your code should look like the following:

//g++ 4.9.3


int my_array[3]= {1, 2, 3};

std::string string_array[2] = {"mammoth", "interactive"};

int main ()
my_array[1] = 5;
std:cout << my_array[1];

Print element one by running the code, and you should see a “5” appear on your screen.

There you have it! To learn even more about coding, sign up for our FREE 30-minute introduction course here: See you soon!

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