Page 83 - PowerPoint Presentation

CAVITE STATE UNIVERSITY
T3 CAMPUS
Department of Information Technology DCIT 25 – Data Structures and Algorithms

The figure above declares a multidimensional array of integers. The first set of array
elements contains three array elements, one for each student. The second set of array
elements has four array elements. The first of the four elements contain student ID and the
other three contains the three grades for that student ID.
In addition to organizing data stored in elements of an array, a multidimensional array
can store memory addresses of data in a pointer array and an array of pointers to pointers.

Multidimensional Array in Memory
Data stored in multidimensional array is stored sequentially by sets of elements, as
shown in the next figure. The first set of four array elements is placed in memory, followed by
the second set of four array elements, and so on.
The name of a multidimensional array references the memory address of the first
element of the first set of four elements. That is, grades is the equivalent of using memory
address 1 in the figure. You can use the name of a multidimensional array as a pointer to the
entire array.
The index of the first element of the first set of array elements points to the memory
address where values assigned to array elements are stored.

Referencing the index of the first dimension points to the memory address of the first
element of that dimension. For example, referencing grades[1] points to memory address 9
in in figure. Memory address 9 is the first memory address of contiguous memory where values
of the set of array elements that are associated with grades[1] are stored.

Declaring a Multidimensional Array
A multidimensional array is declared similar to the way you declare a one-dimensional
array except you specify the number of elements in both dimensions.
int grades[3][4];

The first bracket [3] tells the compiler that you’re declaring 3 pointers, each pointing to
an array. This concept might be confusing because the term “pointer” may make some
programmers think of pointer variable or pointer array. However, we are not talking about a
pointer variable or pointer array. Instead, we are saying that each element of the first
dimension of multidimensional array reference a corresponding second dimension, which is
an array.
In this example, all the arrays pointed to by the first index are of the same size. The
second index can be of variable size. For example, the previous statement declares a two-

Page | 30