An array of arrays in computer programming is a data structure that contains another array at each index. This means that the data at each sequential address in the top-level array is actually the first data element of each subarray. In turn, each sub-array can also be an array of arrays, allowing arrays to be nested to the required depth. While the concept may seem complex, there are actually very simple declarations and dereferencing notations that allow an array of arrays to be expressed very clearly within a program. One of the most common uses of an array of arrays is to store information in a grid pattern, such as an image.
Woman doing handstand with a computer
An array is a series of data elements that, in most programming languages, are stored in consecutive memory locations. The data contained in an array is called an element, and each element occupies a position in the array known as an index. The beginning of an array is index zero, the next is index one, and so on. Instead of containing integers or characters, an array of arrays contains another entire array at each index. These subsets under each index can also contain sets, providing the ability to create complex tree-like data structures as needed.
One of the common uses of an array of arrays is to store information that can be indexed from a grid with column and row coordinates. This can be used to represent data in a spreadsheet, a two-dimensional (2D) image to display on a screen, or even a chessboard. Arrays of arrays three levels deep, that is, an array that contains arrays that contain a third level of arrays, can be used to represent information in a cube, or it can be used to represent an array of information where each location has more than one attribute. In general, arrays of arrays of more than three levels are not used, because the same functionality can be implemented more simply by using an array of structures or classes.
The programming notation for an array of arrays is much easier to figure out than you might expect. Most programming languages use square brackets to indicate the index of an array, and a multidimensional array is no different, except that an additional set of square brackets is added to index the subarray. For example, a one-dimensional array can be written as “array [2]” to denote the element at the second index location of the array. An array of arrays can be written in a similar way: array [2] [1] – indicating the reference element at the first index of the second array.
