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Chapter 3 – Variables, Input, and Output

3.1 Numbers

3.2 Strings

3.3 Input and Output

3.3 Input and Output

• Formatting Output with Format Functions

• Formatting Output with Zones

• Using a Masked Text Box for Input

• Dates as Input and Output

• Getting Input from an Input Dialog Box

• Using a Message Dialog Box for Output

• Named Constants

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Formatting Output with Format Functions

Function String Value

FormatNumber(12345.628, 1) 12,345.6

FormatCurrency(12345.628, 2) $12,345.63

FormatPercent(0.183, 0) 18%

Using Formatting

• Format functions return a string

• Used primarily with Listbox or textboxes

• Examples:Listbox1.items.add(FormatNumber(3523.785,2)

Textbox.text = “Profit = “ & FormatCurrency(32)

String myStr = FormatPercent(0.25,1)

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Formatting Output with Zones

• Use a fixed-width font such as Courier New

• Divide the characters into zones with a format string.

Dim fmtStr As String = "{0, 15}{1, 10}{2, 8}"

lstOutput.Items.Add(String.Format(fmtStr, _

data0, data1, data2))

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Formatting Output with Zones and Justification

Dim fmtStr As String = "{0, -15}{1, 10}{2, 8}"

lstOutput.Items.Add(String.Format(fmtStr, _

data0, data1, data2))

Here, 15 was preceded by a minus sign. This

produces left justification in 0th zone. There will

be right justification in the other two zones.

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Zone Formatting Symbols

Dim fmtStr As String = "{0,15:N1}{1,10:C2}{2,8:P0}"

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Symbols: N, C, and P Effect on zone

:Nr FormatNumber(data, r)

:Cr FormatCurrency(data, r)

:Pr FormatPercent(data, r)

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Masked Text Box Control

Similar to an ordinary text box, but has a Mask property that restricts what can be typed into the masked text box.

Tasks button

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Masked Text Box Control

Click on the Tasks button to reveal the Set Mask property.

Click Set Mask to invoke the Input Mask dialog box.

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Input Mask Dialog Box

• We will use this mask on our next problem.

Mask

A Mask setting is a sequence of characters, with 0, L, and & having special meanings.

•0 Placeholder for a digit.

•L Placeholder for a letter.

•& Placeholder for a character

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Sample Masks

• State abbreviation: LL

• Phone number: 000-0000

• Social Security Number: 000-00-0000

• License plate: &&&&&&

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Dates as Input and Output

• Date literal: #7/4/1776#

• Declarations: Dim indDay As Date Dim d As Date = CDate(txtBox.Text)

Dim indDay As Date = #7/4/1776#

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Date literals are enclosed in #s, just like strings are

enclosed in “s.

Masked Textbox and Dates Example

• Problem: Create a program to compute a person’s age in days.

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Private Sub btnCompute_Click(…) Handles btnCompute.Click Dim d As Date = CDate(mtbDayOfBirth.Text) txtFullDate.Text = FormatDateTime(d, DateFormat.LongDate) txtToday.Text = FormatDateTime(Today, DateFormat.LongDate) txtAgeInDays.Text = FormatNumber(DateDiff(DateInterval.Day, d, Today), 0) End Sub

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Getting Input from an Input Dialog Box

stringVar = InputBox(prompt, title)

fullName = InputBox("Enter your full name.",

"Name")

title

prompt

Inputbox Example

Problem Description: Ask a user for their full name and report their first name in a textbox.

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Private Sub btnDisplay_Click(…) Handles btnDisplay.Click Dim prompt, fullName, firstName, title As String prompt = "Enter your full name." title = "Name" fullName = InputBox(prompt, title) firstName = fullName.Substring(0, fullName.IndexOf(" ")) txtOutput.Text = "Your first name is " & firstName End Sub

InputBox Challenge

• Problem: compute the perfect age for a companion for going on a date. Perfect age = 2/3 your age + 10% age

• Remember to convert the user inputbox to an integer and assign it to a variable.

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Using a Message Dialog Box for Output

MessageBox.Show(prompt, title)

MessageBox.Show("Nice try, but no cigar.",

"Consolation")

title

prompt

Named Constants

• Declared with Const CONSTANT_NAME As DataType = value

• Value cannot be changed.

Examples: Const MIN_VOTING_AGE As Integer = 18

Const INTEREST_RATE As Double = 0.035

Const TITLE As String = "Visual Basic"

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