Visual C# 2005 Programming Guide

Two-Dimensional Arrays

One-Dimensional Arrays In Parallel

The examples on the previous page all refer to arrays with a single dimension. Consider the following representation of a one-dimensonal array,

Element	Student
0	Pinky
1	Perky
2	Bob
3	Agnes
4	Bill
5	McJack
6	Jimbob
7	Gladys

Element	Exam Mark
0	37
1	52
2	41
3	74
4	61
5	87
6	53
7	29

What we have now is two arrays in parallel. This means that our program must keep track of the relationship between the elements of the two arrays but that isn't too difficult since the subscripts match up.

Two-Dimensional Arrays

Suppose we want to store more than one mark for each of our students. We don't want to declare any more one-dimensional arrays because it will make our program very time-consuming to write when we want to process this information. Instead, we declare an array with two dimensions to store the values.

This would give us something like this,

Element	Exam Mark 0	Exam Mark 1	Exam Mark 2	Exam Mark 3	Exam Mark 4
0	37	51	65	69	56
1	52	39	40	41	57
2	41	33	32	75	77
3	74	43	45	50	73
4	61	76	35	57	41
5	87	74	47	65	53
6	53	57	36	33	55
7	29	68	79	61	64

We can declare, initialise and iterate through the two-dimensional array as follows,

int[,] examMarks = { { 37, 51, 65, 69, 56 }, { 52, 39, 40, 41, 57 }, { 41, 33, 32, 75, 77 }, { 74, 43, 45,
       50, 73 }, { 61, 76, 35, 57, 41 }, { 87, 74, 47, 65, 53 }, { 53, 57, 36, 33, 55 }, { 29, 68, 79, 61, 64 } };
for (int i = 0; i < examMarks.GetLength(0); i++)
{
   Console.Write("Marks for student {0}: ", i);
   for (int j = 0; j < examMarks.GetLength(1); j++)
   {
      Console.Write("{0} ",examMarks[i, j]);
   }
   Console.WriteLine();
}
Console.ReadLine();

The array declaration is a bit long and breaks over two lines here.

Having A Go

1. Copy the declaration of the exam marks array. Create an array of student names to match up with this data. Calculate the total and mean average for each student.