microsoft visual basic 2010: reloaded fourth edition chapter nine arrays

Microsoft Visual Basic 2010: Reloaded Fourth Edition

Chapter NineArrays

Microsoft Visual Basic 2010: Reloaded, Fourth Edition

Objectives

After studying this chapter, you should be able to:

• Declare and initialize a one-dimensional array

• Store data in a one-dimensional array

• Determine the number of array elements and the highest subscript

• Traverse a one-dimensional array

• Code a loop using the For Each…Next statement

• Compute the total and average of a one-dimensional array’s contents

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Objectives (cont'd.)

• Find the highest value in a one-dimensional array

• Associate a list box with a one-dimensional array

• Use a one-dimensional array as an accumulator

• Sort a one-dimensional array

• Create and initialize a two-dimensional array

• Store data in a two-dimensional array

• Sum the values in a two-dimensional array

• Search a two-dimensional array

Microsoft Visual Basic 2010: Reloaded, Fourth Edition 3


• 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

Arrays

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One-Dimensional Arrays

• One-dimensional array:– Can be viewed as a column of variables– Each variable in the array has the same name and

data type

• 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

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Figure 9-1: Illustration of the naming convention for the one-dimensional sales array

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One-Dimensional Arrays (cont'd.)

• Element: an individual variable in the array

• When an array is declared:– Must specify the data type, name, and highest

subscript to be used

• First element has a subscript of 0– The array will contain one element more than the

highest subscript because subscripts start at 0

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Figure 9-2: How to declare a one-dimensional array8



• Each element in the array is initialized if no values are provided– String array elements are initialized to the keyword

Nothing– Numeric array elements are initialized to 0– Boolean array elements are initialized to False– Date array elements are initialized to 12:00 AM

January 1, 0001

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• Initial values can be specified for array elements

• Populating the array: assigning initial values to an array

– List the values in a comma-separated list enclosed in curly braces ({})

• After declaration, can use an assignment statement to store a value in an array element

• Length property: indicates number of elements• GetUpperBound method: returns the highest

subscript



Figure 9-3: How to store data in a one-dimensional array

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Figure 9-4: How to use a one-dimensional array’s Length property


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Figure 9-5: How to use a one-dimensional array’s GetUpperBound method


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Traversing a One-Dimensional Array

• Traverse an array: look at each array element, one by one, from beginning to end of the array

• Use a loop to traverse an array

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Figure 9-6: How to traverse a one-dimensional array

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The For Each…Next Statement

• For Each…Next statement: – Used to code a loop that processes each element in a

group or array– Creates a variable used to represent each element in

the group or array– Data type of the element must match the data type of

the group

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The For Each…Next Statement (cont'd.)

Figure 9-7: How to use the For Each…Next statement

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Starward Coffee – Calculating a Total and an Average


Figure 9-9: Problem specification for the Starward Coffee Application

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Starward Coffee – Calculating a Total and an Average (cont’d.)

Figure 9-8: Sample run of the Starward Coffee application

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Figure 9-10: Partial code for the Starward Coffee application

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Figure 9-10: Partial code for the Starward Coffee application (cont’d.)

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Figure 9-10: Partial code for the Starward Coffee application (cont’d.)


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Car-Mart – Finding the Highest Value

Figure 9-11: Problem specification for the Car-Mart application

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Car-Mart – Finding the Highest Value (cont’d.)

Figure 9-12: Sample run of the Car-Mart application

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Figure 9-13: Get Highest button’s Click event procedure

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Hunt Auditorium – Arrays and Collections

Figure 9-14: Problem specification for the Hunt Auditorium application

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Hunt Auditorium – Arrays and Collections (cont'd.)

Figure 9-15: Sample run of the Hunt Auditorium application

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Figure 9-16: Partial code and an illustration for the Hunt Auditorium application

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Figure 9-15: Partial code and an illustration for the Hunt Auditorium application (cont’d.)

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Hinsbrook School – Accumulator Array

Figure 9-17: Problem specification for the Hinsbrook School application

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Hinsbrook School – Accumulator Array (cont'd.)

Figure 9-18: Sample run of the Hinsbrook School application

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Figure 9-19: Partial code for the Hinsbrook School application

Hinsbrook School – Accumulator Array (cont'd.)

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Figure 9-19: Partial code for the Hinsbrook School application (cont’d.)

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Sorting 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

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Figure 9-20: How to use the Array.Sort and Array.Reverse methods

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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

• Refer to an element using the name followed by the (row, column) pair in parentheses

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Figure 9-21: Names of some of the variables contained in the two-dimensional orders array

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Two-Dimensional Arrays (cont'd.)

• 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

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Figure 9-22: How to declare a two-dimensional array

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Two-Dimensional Arrays (cont'd.)


Figure 9-23: How to store data in a two-dimensional array


Figure 9-23: How to store data in a two-dimensional array (cont’d.)

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Figure 9-24: How to use a two-dimensional array’s GetUpperBound method

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Traversing a Two-Dimensional Array

• To traverse a two-dimensional array, use two loops:– Outer loop: tracks the row subscript– Nested loop: tracks the column subscript

• Can also use a For Each…Next loop



Traversing a Two-Dimensional Array (cont'd.)

Figure 9-25: How to traverse a two-dimensional array

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Figure 9-25: How to traverse a two-dimensional array (cont’d.)

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Figure 9-26: Problem specification for the Jenko Booksellers application

Jenko Booksellers – Calculating a Total

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Figure 9-27: Sample run of the Jenko Booksellers application

Jenko Booksellers – Calculating a Total (cont’d.)

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Figure 9-28: Calculate button’s Click event procedure

Jenko Booksellers – Calculating a Total (cont’d.)

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Figure 9-29: Problem specification for the O’Reilly Studios application

O’Reilly Studios – Searching a Two-Dimensional Array

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Figure 9-30: Sample run of the O’Reilly Studios application

O’Reilly Studios – Searching a Two-Dimensional Array (cont’d.)

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Figure 9-31: Partial code for the O’Reilly Studios application

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• Lottery Game application– Generates and displays six unique random numbers

for a Lottery Game


Programming Tutorial 1

Figure 9-33: MainForm in the Lottery Game application

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• Stay Fit Health Club application– Displays monthly fees for three different membership

levels


Programming Tutorial 2

Figure 9-33: MainForm for the Stay Fit Health Club application

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• Professor Coleman application– Allows a user to select a letter grade from a list box


Programming Example

Figure 9-43: MainForm in the Professor Coleman application

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Summary

• Arrays: used to store related data in memory

• All variables in an array have the same name and data type

• To declare a one-dimensional array, provide the highest subscript or initial values

• One-dimensional array: each element is uniquely identified by its position (subscript) in the array

• Refer to an element in a one-dimensional array by using array name and element’s subscript


Summary (cont'd.)

• Length property: returns the number of elements in an array

• GetUpperBound method: returns the highest subscript in the array

• Use a loop to traverse a one-dimensional array

• Can use variables in an array as accumulators• 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



Summary (cont'd.)

• Two-dimensional array: each element is uniquely identified by its position (row and column subscripts) in the array

• To declare a two-dimensional array, provide the highest row and column subscripts or initial values

• Number of rows in a two-dimensional array is the highest row subscript value + 1

• Number of columns in a two-dimensional array is the highest column subscript value + 1

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Summary (cont'd.)

• Refer to an element in a two-dimensional array by using array name and element’s row and column subscripts separated by a comma

• Use a two-dimensional array’s GetUpperBound method to determine the highest row subscript and the highest column subscript in the array

• Can traverse a two-dimensional array using either two loops (outer loop and nested loop) or the For Each…Next statement


microsoft visual basic 2010: reloaded fourth edition chapter nine arrays

Documents

array use array

memory array

onedimensional sales

onedimensional array

number of array elements

boolean array elements

numeric array elements

string array elements