Initializing the Elements of a Multidimensional Array

As with any array, we can initialize the elements of a multidimensional array by providing a bracketed list of initializers. Multidimensional arrays may be initialized by specifying bracketed values for each row:

int ia[3][4] = {    // three elements; each element is an array of size 4
    {0, 1, 2, 3},   // initializers for the row indexed by 0
    {4, 5, 6, 7},   // initializers for the row indexed by 1
    {8, 9, 10, 11}  // initializers for the row indexed by 2
};

The nested braces are optional. The following initialization is equivalent, although considerably less clear:

// equivalent initialization without the optional nested braces for each row
int ia[3][4] = {0,1,2,3,4,5,6,7,8,9,10,11};

As is the case for single-dimension arrays, elements may be left out of the initializer list. We can initialize only the first element of each row as follows:

// explicitly initialize only element 0 in each row
int ia[3][4] = {{ 0 }, { 4 }, { 8 }};

The remaining elements are value initialized in the same way as ordinary, single-dimension arrays (§ 3.5.1, p. 114). If the nested braces were omitted, the results would be very different. This code

// explicitly initialize row 0; the remaining elements are value initialized
int ix[3][4] = {0, 3, 6, 9};

initializes the elements of the first row. The remaining elements are initialized to 0.