The C programming language allows multidimensional arrays. Here is the general form of a multidimensional array declaration −
type name[size1][size2]...[sizeN];
For example, the following declaration creates a three dimensional (5 x 10 x 4) integer array:
int arr[5][10][4];
Two-dimensional Arrays
The simplest form of multidimensional array is the two-dimensional array. A two-dimensional array is, in essence, a list of one-dimensional arrays. To declare a two-dimensional integer array of dimensions m x n, we can write as follows:
type arrayName[m][n];
Where type
can be any valid C data type (int
, float
, etc.) and arrayName
can be any valid C identifier. A two-dimensional array can be visualized as a table with m
rows and n
columns. Note: The order does matter in C. The array int a[4][3]
is not the same as the array int a[3][4]
. The number of rows comes first as C is a row-major language.
A two-dimensional array a
, which contains three rows and four columns can be shown as follows:
Thus, every element in the array a
is identified by an element name of the form a[i][j]
, where a
is the name of the array, i
represents which row, and j
represents which column. Recall that rows and columns are zero indexed. This is very similar to mathematical notation for subscripting 2-D matrices.
Initializing Two-Dimensional Arrays
Multidimensional arrays may be initialized by specifying bracketed values for each row. The following define an array with 3 rows where each row has 4 columns.
int a[3][4] = {
{0, 1, 2, 3} , /* initializers for row indexed by 0 */
{4, 5, 6, 7} , /* initializers for row indexed by 1 */
{8, 9, 10, 11} /* initializers for row indexed by 2 */
};
The nested braces, which indicate the intended row, are optional. The following initialization is equivalent to the previous example:
int a[3][4] = {0,1,2,3,4,5,6,7,8,9,10,11};
While the method of creating arrays with nested braces is optional, it is strongly encouraged as it is more readable and clearer.
Accessing Two-Dimensional Array Elements
An element in a two-dimensional array is accessed by using the subscripts, i.e., row index and column index of the array. For example −
int val = a[2][3];