What is a 2D array in C/C++?

An array is a data type in C/C++ used to hold sequence objects with the same data type.

Consider we have a string with multiple characters. How would we store and represent the string in our program? Here, we can initialize a char array object in C/C++ with the string.

What is a 2D array?

A 2D array is referred to as an array of arrays. Below is a diagram showing what 2D arrays are and how they are represented.

On the left side, we see an array represented by red. Each cell in the array contains another array represented on the right by the green color.

A 2D array can be imagined as a matrix with rows and columns where the rows represent the individual arrays, while the columns represent the elements of those arrays.

For example, if we want to retrieve the number 11 in our 2D array represented in the diagram, we would have to start with the row value, which is 2, and the column value, which is 1. We can access it using the index [2][1] in our 2D array.

Syntax

Below, we can see the syntax used to create a 2D array in C/C++:

Below, we can see what these placeholders mean:

• dataType: The type of elements that we want to store in the array. The data type of the array should be the same as the elements.

• rowSize: The number of rows we want in our 2D array object, which represents arrays.

• columnSize: The number of elements that each array can contain.

Example

Let's suppose we have to make a tic-tac-toe game in C/C++. We need a data object to store a 3x3 matrix representing the 9 boxes in a tic-tac-toe game.

Here, we can create a character array with 3 rows and 3 columns so our array declaration would look like the following line of code.

Here, we will use the dataType of char since we have to store characters X and O as inputs to the 2D array.

Code example

Below, we can see a sample C application that shows how to create a 2D array named numbers of size 4x4 to store numbers and uses two for loops to loop over the elements in the array and print them onto the console.

Code explanation

• Lines 4–7: We create and initialize a 2D int array named numbers with 4 rows and 4 columns.

• Lines 9–14: We use two for loops to print each element in the 2D numbers array and format the output to display each array/row in one line.

Practice questions

Now that we have gone over 2D arrays in C/C++ and how we can perform array manipulation operations on the array, let's try to solve the practice questions below.