OOP with C# by Dr.hakim

1. Ar rays(I)
Lecture 8
Dr. Hakem Beitollahi
Computer Engineering Department
Soran University

2. Outline
 Arrays
 Declaring and allocating arrays
 Examples using arrays
Arrays(I)— 2

3. Arrays
Arrays(I)— 3

4. Arrays (I)
 An array is a group of contiguous memory locations that
all have the same name and type
 To refer to a particular location or element in the array,
we specify the name of the array and the position
number
 Array indexes
 Position number used to refer to a specific location/element
 Also called subscript
 Place in square brackets
o Must be positive integer or integer expression
 First element has index zero
 Example (assume a = 5 and b = 6)
o c[ a + b ] = c[11] = 2;
Arrays(I)— 4

5. Arrays (II)
Arrays(I)— 5

6. Arrays (III)
A -- -- -- --
-- -- -- -- -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
Arrays(I)— 6
 Suppose
int[] A = new int [10]; // array of
10 uninitialized ints
 To access an individual element we
must apply a subscript to list name A

7. Arrays (IV)
Arrays(I)— 7
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A -- -- -- --
-- -- -- -- -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

8. Arrays (V)
Arrays(I)— 8
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- -- --
-- -- -- -- -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

9. Arrays (VI)
Arrays(I)— 9
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- -- --
-- -- -- 5 -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

10. Arrays (VII)
Arrays(I)— 10
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- 8 --
-- -- -- 5 -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

11. Arrays (VIII)
Arrays(I)— 11
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- 8 6
-- -- -- 5 -- --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

12. Arrays (IX)
Arrays(I)— 12
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- 8 6
-- -- -- 5 12 --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

13. Arrays (X)
Arrays(I)— 13
 Consider
int i = 7, j = 2, k = 4;
A[0] = 1;
A[i] = 5;
A[j] = A[i] + 3;
A[j+1] = A[i] + A[0];
A[A[j]] = 12;
A 1 -- 8 6
3 -- -- 5 12 --
A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]

14. Common Programming Error 7.1
 It is important to note the difference between the
“seventh element of the array” and “array element
seven.” Array subscripts begin at 0, thus the “seventh
element of the array” has a subscript of 6, while “array
element seven” has a subscript of 7 and is actually the
eighth element of the array.
Arrays(I)— 14

15. Array Definition (I)
Arrays(I)— 15

16. Array Definition (II)
 When arrays are allocated, the elements are initialized to
zero for the numeric primitive data-type variables, to
false for bool variables and to null for reference types.
 Multiple declaration in single line:
 In an array of value types, every element of the array
contains one value of the declared type.
 For example, every element of an int array is an int value.
Arrays(I)— 16
string[] b = new string[ 100 ], x = new
string[ 27 ];
double[] array1 = new double[ 10 ],
array2 = new double[ 20 ];

17. Examples Using Arrays
Arrays(I)— 17

18. Initializing the elements of an array
 Example 1: Allocating an Array and
Initializing Its Elements
 The program creates three integer arrays of
10 elements and displays those arrays in
tabular format. The program demonstrates
several techniques for declaring and
initializing arrays
Arrays(I)— 18

19. Arrays(I)— 19

20. Summing the elements of an array
 Example 2: Totaling the Elements of an
Array
 Often, the elements of an array represent
series of values to be used in calculations.
 Elements of an array represent the grades for
an exam, the professor may wish to total the
elements, then calculate the class average.
Arrays(I)— 20

21. Arrays(I)— 21

22. Histogram Example
 Example 3: Using Histograms to
Display Array Data Graphically
 Many programs present data to users in a
graphical manner
 Numeric values often are displayed as bars in
a bar chart.
 In such a chart, longer bars represent larger
numeric values.
 One simple way to display numeric data
graphically is with a histogram that shows
each numeric value as a bar of asterisks (*).
Arrays(I)— 22

23. Arrays(I)— 23
Show length of an array

24. Use arrays as counters
 Example 4: Using the Elements of an Array as Counters
 Sometimes programs use a series of counter variables to summarize
data, such as the results of a survey.
 Calculate the number of occurrences of each side on a six-sided
die
Arrays(I)— 24

25. Arrays(I)— 25