Microsoft Visual Basic 2005: Reloaded Second Edition

Microsoft Visual Basic 2005: Reloaded Second Edition Chapter 8 Arrays

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

One-Dimensional Arrays (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

Storing Data in a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

Displaying the Contents of a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

Displaying the Contents of a One-Dimensional Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

The For Each…Next Statement (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Using the Subscript to Access an Element in a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

Using the Subscript to Access an Element … (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Searching a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

Searching a One-Dimensional Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

Calculating the Average Amount Stored in a One-Dimensional Numeric Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Determining the Highest Value Stored in a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

Determining the Highest Value Stored in a One-Dimensional Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Updating the Values Stored in a One-Dimensional Array Microsoft Visual Basic 2005: Reloaded, Second Edition

Updating the Values Stored in a One-Dimensional Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

Sorting the Data Stored in a One-Dimensional Array (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Parallel One-Dimensional Arrays Microsoft Visual Basic 2005: Reloaded, Second Edition

Parallel One-Dimensional Arrays (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Parallel One-Dimensional Arrays (continued) • Parallel arrays: • Two or more arrays whose elements are related by their position in the arrays Microsoft Visual Basic 2005: Reloaded, Second Edition

Parallel One-Dimensional Arrays (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

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 Microsoft Visual Basic 2005: Reloaded, Second Edition

Two-Dimensional Arrays (continued) Microsoft Visual Basic 2005: Reloaded, Second Edition

Microsoft Visual Basic 2005: Reloaded Second Edition