Arrays
Objectives
• Declare and initialize a one-dimensional array
• Store data in a one-dimensional array
• Display the contents of a one-dimensional array
• Code a loop using the For Each…Next statement
• Access an element in a one-dimensional array
• Search a one-dimensional array
• Compute the average of a one-dimensional array’s
contents
• Find the highest entry in a one-dimensional array
• Update the contents of a one-dimensional array
• Sort a one-dimensional array
Objectives (cont’d)
• Create and manipulate parallel one-dimensional
arrays
• Create a structure
• Declare a structure variable
• Create and manipulate a one-dimensional array
of structures
• Create and initialize a two-dimensional array
• Store data in a two-dimensional array
• Search a two-dimensional array
Arrays
• A simple or scalar variable is one that is
unrelated to any other variable in memory
• An array is a group of variables that have
the same name and data type and are
related in some way
Arrays (continued)
• The most commonly used arrays are onedimensional and two-dimensional
• Programmers use arrays to store related
data in the internal memory of the
computer
One-Dimensional Arrays
• A one-dimensional array is simply a row
(or column) of variables
• Each element in an array is identified by a
subscript, which Visual Basic .NET
assigns to the variable when the array is
created
One-Dimensional Arrays
(continued)
• You refer to each variable in an array by its
name and the variable’s subscript
Names of the variables in a one-dimensional array named
states
One-Dimensional Arrays
(continued)
• Declaring a one-dimensional array
– Version 1
{Dim | Private} arrayname(highestSubscript)
As datatype
– Version 2
{Dim | Private} arrayname() As datatype =
{initialValues}
One-Dimensional Arrays
(continued)
• Examples of declaring an array
– Dim cities(3) As String
– Private states() As String = {“Hawaii”,
“Alaska”, “Maine”}
Storing Data in a OneDimensional Array
• In most cases, you use an assignment
statement to enter data into an existing
array
• Syntax: arrayname(subscript) = value
• Examples
– cities(0) = “Madrid”
– cities(1) = “Paris”
– cities(2) = “Rome”
Manipulating One-Dimensional
Arrays
• You will learn how to perform the following
tasks using a one-dimensional array:
– Display the contents of an array
– Access an array element using its subscript
– Search the array
– Calculate the average of the data stored in a
numeric array
Manipulating One-Dimensional
Arrays (continued)
• You will learn how to perform the following
tasks using a one-dimensional array
(continued):
– Find the highest value stored in an array
– Update the array elements
– Sort the array elements
Displaying the Contents of a
One-Dimensional Array
• uiDisplayButton’s Click event procedure
– Demonstrates how you can display the
contents of an array in a label control
– Uses the For…Next statement to display each
array element
– You also could use the Do…Loop statement
or the For Each…Next statement
Displaying the Contents of a
One-Dimensional Array
(continued)
uiDisplayButton’s Click event procedure
The For Each…Next Statement
Syntax and an example of the For Each…Next statement
Using the Subscript to Access
an Element in a OneDimensional Array
• XYZ Corporation pays its managers based
on six different salary codes, 1 through 6
• Each code corresponds to a different
salary
• uiSalaryButton’s Click event procedure
displays the salary corresponding to the
code entered by the user
Searching a One-Dimensional
Array
• The sales manager at Jacobsen Motors
wants a procedure that allows him to
determine the number of salespeople
selling above a certain amount, which he
will enter
• uiSearchButton’s Click event procedure
searches the array, looking for values that
are greater than the amount entered by
the sales manager
Calculating the Average Amount
Stored in a One-Dimensional
Numeric Array
• uiCalcAvgButton’s Click event procedure
calculates and displays the average test
score
uiCalcAvgButton’s Click event procedure
Calculating the Average Amount
Stored in a One-Dimensional
Numeric Array (continued)
uiCalcAvgButton’s Click event procedure (continued)
Determining the Highest Value
Stored in a One-Dimensional
Array
• Sharon Johnson wants a procedure that
displays the highest amount she has
earned in a week
• uiHighestButton’s Click event procedure
will search the array, looking for the
highest amount
Updating the Values Stored in a
One-Dimensional Array
• The sales manager at Jillian Company
wants a procedure that:
– Allows her to increase the price of each item
the company sells
– Displays each item’s new price in the
uiNewPricesLabel control
• uiUpdateButton’s Click event procedure
performs these tasks
Sorting the Data Stored in a
One-Dimensional Array
• Arranging data in a specific order is called
sorting
• Array.Sort method
– Can be used to sort the elements in a one-
dimensional array in ascending order
– Syntax: Array.Sort(arrayname)
• uiSortButton’s Click event procedure uses
the Array.Sort method to sort the numbers
array in ascending order
Sorting the Data Stored in a
One-Dimensional Array
(continued)
• To sort a one-dimensional array in
descending order:
– Use Array.Sort to sort the array in ascending
order
– Use Array.Reverse to reverse the array
elements
• Syntax of the Array.Reverse method:
Array.Reverse(arrayname)
Using a Module-Level OneDimensional Array
• Names application
– Needs to display the names contained in a
sequential access file
– Should give the user the choice of displaying
the names in either ascending or descending
order
• The names array is declared in the form’s
Declarations section, making it a modulelevel array
Parallel One-Dimensional
Arrays
• Arrays that are related by an element’s
position (subscript)
• Searching one array gives you the
subscript for the other array
• To store a price list, which includes a string
and a number, you can use two onedimensional arrays
– A String array to store the product IDs
– An Integer array to store the prices
Parallel One-Dimensional
Arrays (continued)
Illustration of a price list stored in two one-dimensional arrays
Structures
• Structure statement: can be used to create
your own data types in Visual Basic .NET
• Data types created using the Structure
statement are referred to as user-defined
data types or structures
• Members included in the structure can be
variables, constants, or procedures
• In most cases, members are variables
Structures (continued)
Syntax and an example of the Structure statement
Using a Structure to Declare a
Variable
• Variables declared using a structure are
often referred to as structure variables
Syntax and an example of declaring a structure variable
Using a Structure to Declare a
Variable (continued)
Syntax and examples
of storing data in a
member variable
Creating an Array of Structure
Variables
• Assigning initial values to an array is
referred to as populating the array
• Refer to a member variable in an array
element using the syntax:
arrayname(subscript).memberVariableNa
me
Two-Dimensional Arrays
• A two-dimensional array resembles a table
in that the variables are in rows and
columns
Illustration of a two-dimensional array
Two-Dimensional Arrays
(continued)
• Each variable (element) in a twodimensional array is identified by a unique
combination of two subscripts
• The subscripts specify the variable’s row
and column position in the array
• Refer to each variable in a twodimensional array by the array’s name and
the row and column subscripts
Two-Dimensional Arrays
(continued)
Syntax versions and examples of declaring a two-dimensional
array
Storing Data in a TwoDimensional Array
Syntax and examples of
entering data into a twodimensional array
Searching a Two-Dimensional
Array
uiDisplayPriceButton’s Click event procedure using a twodimensional array
Searching a Two-Dimensional
Array (continued)
uiDisplayPriceButton’s
Click event procedure
using a twodimensional array
(continued)
The Tax Calculator Application
• John Blackfeather, the owner and
manager of the Perrytown Gift Shop,
should be able to use the application to
calculate the weekly federal withholding
tax for his employees
• To calculate the federal withholding tax,
the user would need to enter the taxable
wages in the Taxable wages text box and
then click the Calculate Tax button
The Tax Calculator Application
(continued)
Interface for the Tax Calculator application
The Tax Calculator Application
(continued)
TOE chart for the Tax Calculator application
Coding the uiCalculateButton
Click Event Procedure
Pseudocode for the uiCalculateButton’s Click event procedure
Coding the uiCalculateButton
Click Event Procedure
(continued)
Pseudocode for the uiCalculateButton’s Click event procedure
(continued)
Summary
• Two versions of the syntax used to declare
a one-dimensional array:
– {Dim | Private} arrayname(highestSubscript)
As datatype
– {Dim | Private} arrayname() As datatype =
{initialValues}
Summary (continued)
• To refer to a variable in an array, use the
array’s name followed by the variable’s
subscript
• To create parallel one-dimensional arrays,
create two one-dimensional arrays
• To create an array of structures, use the
Structure statement to create a record
structure, then use the record structure to
declare the array
Summary (continued)
• Two versions of the syntax used to declare a
two-dimensional array:
– {Dim | Private} arrayname(highestRowSubscript,
highestColumnSubscript) As datatype
– {Dim | Private} arrayname(,) As datatype =
{{initialValues}, {initialValues},…{initialValues}}
• Syntax used to refer to a variable included in a
two-dimensional array:
arrayname(rowSubscript, columnSubscript)