Array data structure

In programming languages, an array is a way of storing several items (such as integers). These items must have the same type (only integers, only strings, ...) because an array can not store different kinds of items. Every item in an array has a number so the programmer can get the item by using that number. This number is called the index. In most programming languages, the first item has index 0, the second item has index 1 and so on.

When the programmer creates an array, they must give the size of the array. This is the number of items that can be stored in the array. If the programmer wants to store more items, then they must create a new array. This is because the size of an array can not be changed.

Arrays in C

In the programming language C, arrays can be created like this: <syntaxhighlight lang="c"> int array[5]; </syntaxhighlight>

This creates an array of integers and it can store 5 integers. The programmer can now store integers in the array by doing: <syntaxhighlight lang="c"> array[0] = 1; array[1] = 18; array[2] = 5; array[3] = 33; array[4] = 50; </syntaxhighlight>

The programmer can use a value in the array like this: <syntaxhighlight lang="c"> int k = 3 + array[3]; // k is now 3 + 33 = 36 </syntaxhighlight>

Arrays in Java

In the programming language Java, arrays can be created like this: <syntaxhighlight lang="java"> int[] array = new int[5]; </syntaxhighlight>

This creates an array of integers and it can store 5 integers. The programmer can now store integers in the array by doing: <syntaxhighlight lang="java"> array[0] = 1; array[1] = 18; array[2] = 5; array[3] = 33; array[4] = 50; </syntaxhighlight>

The programmer can use a value in the array like this: <syntaxhighlight lang="java"> int k = 3 + array[3]; // k is now 3 + 33 = 36 </syntaxhighlight>

Array Data Structure Media

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  Illustration of row- and column-major order

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  A two-dimensional array stored as a one-dimensional array of one-dimensional arrays (rows).