Microsoft Visual Basic 2005: Reloaded Second Edition

Microsoft Visual Basic 2005: Reloaded

Second Edition

Chapter 8Arrays

Microsoft Visual Basic 2005: Reloaded, Second Edition 2

Objectives

After studying this chapter, you should be able to:

• 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


Objectives (continued)

• 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 (continued)

• Create and manipulate parallel one-dimensional arrays

• Create and initialize a two-dimensional array• Store data in a two-dimensional array• Search a two-dimensional array


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


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


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


Storing Data in a One-Dimensional Array


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


Displaying the Contents of a One-Dimensional Array


Displaying the Contents of a One-Dimensional Array (continued)


Displaying the Contents of a One-Dimensional Array (continued)


The For Each…Next Statement

• For Each…Next 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


The For Each…Next Statement (continued)


Using the Subscript to Access an Element in a One-Dimensional Array


Using the Subscript to Access an Element … (continued)


Using the Subscript to Access an Element … (continued)


Searching a One-Dimensional Array


Searching a One-Dimensional Array (continued)






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



Numeric Array (continued)











Determining the Highest Value Stored in a One-Dimensional Array



(continued)



(continued)


Updating the Values Stored in a One-Dimensional Array


Updating the Values Stored in a One-Dimensional Array (continued)






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


Sorting the Data Stored in a One-Dimensional Array (continued)






Parallel One-Dimensional Arrays


Parallel One-Dimensional Arrays (continued)



• Parallel arrays: – Two or more arrays whose elements are related by

their position in the arrays










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


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


Storing Data in a Two-Dimensional Array


Storing Data in a Two-Dimensional Array (continued)


Searching a Two-Dimensional Array


Searching a Two-Dimensional Array (continued)






Programming Tutorial


Programming Example


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


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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Microsoft Visual Basic 2005: Reloaded Second Edition

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