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Microsoft Visual Basic 2005: Reloaded Second Edition

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Microsoft Visual Basic 2005: Reloaded Second Edition Chapter 8 Arrays – PowerPoint PPT presentation

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Title: Microsoft Visual Basic 2005: Reloaded Second Edition


1
Microsoft Visual Basic 2005 Reloaded Second
Edition
  • Chapter 8
  • Arrays

2
Using Arrays
  • Simple variable (or scalar variable) a variable
    that is unrelated to any other variable in memory
  • Array
  • A group of variables with the same name and data
    type that are related in some way
  • Used to temporarily store related data in memory
  • Increases the efficiency of a program
  • Commonly used arrays
  • One-dimensional
  • Two-dimensional

3
One-Dimensional Arrays
  • One-dimensional array
  • Can be viewed as a column of variables
  • Subscript
  • A unique number that identifies each variable in
    a one-dimensional array
  • Starts at 0 for first element in the array
  • Use array name and subscript to refer to each
    individual variable in the array

4
One-Dimensional Arrays
Score(0)
Score(4)
5
One-Dimensional Arrays (continued)
6
One-Dimensional Arrays (continued)
7
One-Dimensional Arrays (continued)
  • Element an individual variable in the array
  • When an array is declared
  • Each element in the array is initialized if no
    values are provided
  • Initial values can be specified for elements

8
Storing Data in a One-Dimensional Array
9
Manipulating One-Dimensional Arrays
  • Array elements can be used like any other
    variable
  • Examples
  • Display the contents of an array
  • Access an array element using its subscript
  • Search the array
  • Calculate the average of data stored in a numeric
    array
  • Find the highest value stored in an array
  • Update array elements
  • Sort array elements

10
Displaying the Contents of a One-Dimensional
Array
11
Displaying the Contents of a One-Dimensional
Array (continued)
12
Displaying the Contents of a One-Dimensional
Array (continued)
13
The For EachNext Statement
  • For EachNext statement
  • Used to code a loop which processes each element
    in a group or array
  • Creates a variable used to represent each item in
    the group or array
  • Data type of the element must match the data type
    of the group

14
The For EachNext Statement (continued)
15
Using the Subscript to Access an Element in a
One-Dimensional Array
16
Using the Subscript to Access an Element
(continued)
17
Subscript to Access an Element
"C0" Currency, no DP.
18
Searching a One-Dimensional Array
19
Searching a One-Dimensional Array (continued)
20
Searching a One-Dimensional Array (continued)
How many elements?
Highest Subscript?
21
Searching a One-Dimensional Array
Could this be done with a For/Next loop?
Whats Wrong with a For/Next loop?
22
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array
  • Sample application
  • Find the average from an array of test scores
  • Length property number of elements in the array

23
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array (continued)
24
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array (continued)
25
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array (continued)
26
Calculating the Average Amount Stored in a
One-Dimensional Numeric Array (continued)
Could this have been done another way?
27
Determining the Highest Value Stored in a
One-Dimensional Array
28
Determining the Highest Value Stored in a
One-Dimensional Array (continued)
29
Determining the Highest Value Stored in a
One-Dimensional Array (continued)
30
Updating the Values Stored in a One-Dimensional
Array
31
Updating the Values Stored in a One-Dimensional
Array (continued)
32
Updating the Values Stored in a One-Dimensional
Array (continued)
33
Updating the Values Stored in a One-Dimensional
Array (continued)
34
Sorting the Data Stored in a One-Dimensional
Array
  • Sorting arranging data in a specific order
  • Ascending first element is smallest, last
    element is largest
  • Descending first element is largest, last
    element is smallest
  • Array.Sort method used to sort elements in a
    one-dimensional array in ascending order
  • Array.Reverse method used after Array.Sort
    method to change to descending order

35
Sorting the Data Stored in a One-Dimensional
Array (continued)
36
Sorting the Data Stored in a One-Dimensional
Array (continued)
37
Parallel One-Dimensional Arrays
38
Parallel One-Dimensional Arrays (continued)
39
Parallel One-Dimensional Arrays (continued)
  • Parallel arrays
  • Two or more arrays whose elements are related by
    their position in the arrays

40
Parallel One-Dimensional Arrays (continued)
41
Parallel One-Dimensional Arrays (continued)
42
Parallel One-Dimensional Arrays (continued)
43
Two-Dimensional Arrays
  • Two-dimensional array
  • Resembles a table with rows and columns
  • Each element is identified by a unique
    combination of two subscripts (row, column)
  • Subscripts are zero-relative

44
Two-Dimensional Arrays (continued)
45
Two-Dimensional Arrays (continued)
46
Two-Dimensional Arrays (continued)
47
Two-Dimensional Arrays (continued)
  • Two-dimensional array
  • Declared with highest row subscript and highest
    column subscript (zero-relative)
  • Number of rows highest row subscript 1
  • Number of columns highest column subscript 1
  • Can specify initial values for array elements
  • If no initial values are declared, array elements
    are automatically initialized

48
Storing Data in a Two-Dimensional Array
49
Storing Data in a Two-Dimensional Array
(continued)
50
Searching a Two-Dimensional Array
51
Searching a Two-Dimensional Array (continued)
52
Searching a Two-Dimensional Array (continued)
53
Searching a Two-Dimensional Array (continued)
54
Programming Tutorial
55
Programming Example
56
Summary
  • Arrays a group of related variables with the
    same name and same data type
  • Array element one item in the array
  • One-dimensional array each element is uniquely
    identified by its position (subscript) in the
    array
  • Two-dimensional array each element is uniquely
    identified by its position (row and column
    subscripts) in the array
  • Subscripts are zero-relative

57
Summary (continued)
  • Number of elements in an array is the highest
    subscript value 1
  • For Each...Next statement used to loop through
    all the elements in an array
  • Length property returns the number of elements
    in an array
  • Array.Sort method sorts the elements in a
    one-dimensional array in ascending order
  • Array.Reverse method reverses the order of
    elements in a one-dimensional array
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