A postfix expression followed by an expression in square brackets ([ ]) is a subscripted representation of an element of an array object. A subscript expression represents the value at the address that is expression positions beyond postfix-expression when expressed as
postfix-expression [ expression ]
Usually, the value represented by postfix-expression is a pointer value, such as an array identifier, and expression is an integral value. However, all that is required syntactically is that one of the expressions be of pointer type and the other be of integral type. Thus the integral value could be in the postfix-expression position and the pointer value could be in the brackets in the expression, or “subscript,” position.
A subscript expression can also have multiple subscripts, as follows:
expression1 [expression2] [expression3]...
Subscript expressions associate from left to right. The leftmost subscript expression, expression1[expression2], is evaluated first. The address that results from adding expression1 and expression2 forms a pointer expression; then expression3 is added to this pointer expression to form a new pointer expression, and so on until the last subscript expression has been added. The indirection operator (*) is applied after the last subscripted expression is evaluated, unless the final pointer value addresses an array type.
Expressions with multiple subscripts refer to elements of “multidimensional arrays.” A multidimensional array is an array whose elements are arrays. For example, the first element of a three-dimensional array is an array with two dimensions.
Example
The following example declares a three-dimensional array for 366 days, in each of 12 months, over a period of 10 years:
// Example of the array element operator
int nYearsMonthsDays[10][12][366];