Download Visual Basic Application

CIS 115 Lecture 4
 Create a Windows-based application that will
calculate the Gross Pay earned for a worker,
given the number of hours worked and hourly
pay rate.

Clearly define the problem and identify what the
program is to do
 Purpose: To calculate a worker’s gross pay
 Input: Number of hours worked, hourly pay rate
 Process: Multiply number of hours worked by
hourly pay rate (result is the user’s gross pay)
 Output: Display a message indicating the user’s
gross pay
Traditional Procedural Approach - Develop an algorithm:
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Display message: "How many hours did you work?"
Allow user to enter number of hours worked
Store the number the user enters in memory
Display message: "How much are you paid per hour?"
Allow the user to enter an hourly pay rate
Store the number the user enters in memory
Multiply hours worked by pay rate and store the result in
memory
Display a message with the result of the previous step
This well-defined, ordered set of steps for solving a problem
is called an algorithm.
VB (GUI) Approach – Identify required controls and events/handlers

Inputs - entered into the program via Controls:
 Hours Worked
 Hourly Pay Rate

Processes - initiated by Events and carried out by the
code contained in the corresponding Event Procedures:
 Calculate Gross Pay
▪ Gross Pay = hoursWorked * hourlyPayRate

Output - displayed to the user via Controls:
 Gross Pay
 Inputs (controls):
 Hours Worked  Textbox, Label (title/prompt)
 Hourly Pay Rate  Textbox, Label (title/prompt)
 Processes (events/event procedures):
 Calculate Gross Pay  Button(click)
▪ Gross Pay = hoursWorked * hourlyPayRate
 Exit Program  Button(click)
▪ End
 Outputs (controls):
 Gross Pay Earned  Label (display result), Label (title)
Design the Interface – TOE Chart
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Task, Object, Event
Plan the interface BEFORE creating in VB
Examines all of the tasks involved in solution
Task (T)
Object (O)
Event (E)
Input Hours Worked
Textbox, Label
None
Input Pay Rate
Textbox, Label
None
Output Gross Pay
Label (display), Label
(title)
None
Calculate Gross Pay
Button
Click
Exit Program
Button
Click

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Make a list of the controls needed
Define values for each control's relevant properties:
Control Type
Form
TextBox
Label
TextBox
Label
Label
Label
Button
Button
Control Name
(Default)
txtHoursWorked
(Default)
txtPayRate
(Default)
lblGrossPay
(Default)
btnCalcGrossPay
btnExit
Text
"Wage Calculator"
""
"Number of Hours Worked"
""
"Hourly Pay Rate"
"$0.00"
"Gross Pay Earned"
"Calculate Gross Pay"
“Exit"
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Make a list the events/procedures needed
Develop an algorithm for each procedure
Event
btnCalcGrossPay_Click
Event Procedure Code Algorithm
Get hours worked from txtHoursWorked
Get hourly pay rate from txtPayRate
Multiply hours worked by hourly pay rate
Assign result to lblGrossPay
btnClose_Click
End the application

Visualize the application running on the computer and design
its user interface
 Creating the Visual Basic Application - Event
Driven Programming Steps
 Create the Interface / Window first
▪ Input
▪ Output
 Set the Properties
▪ Configure the appearance and behavior of the controls
 Then Code the Application
▪ Processes - Event Handing Methods

Create the Interface - Use Visual Basic to create the forms
and other controls identified in the previous step
 This is the first use of Visual Basic, all of the previous
steps have just been on paper
 In this step you develop the portion of the application
the user will see
Label
Label
Label
2 Buttons
Text Box
Text Box
Label

Set Properties - Use Visual Basic to set properties for the
forms and other controls from list you made earlier
 In this step you still developing the portion of the
application the user will see
Control Type
Form
TextBox
Label
TextBox
Label
Label
Label
Button
Button
Control Name
(Default)
txtHoursWorked
(Default)
txtPayRate
(Default)
lblGrossPay
(Default)
btnCalcGrossPay
btnExit
Text
"Wage Calculator"
""
"Number of Hours Worked"
""
"Hourly Pay Rate"
"$0.00"
"Gross Pay Earned"
"Calculate Gross Pay"
“Exit"

Create the Events/Procedures - Use Visual Basic to create
and write the code for the event procedures identified
earlier
 In this step you develop the methods behind the click
event for each button
 Unlike the interface, this portion of the application is
invisible to the user

btnCalculate
 Button Click Event
 Assignment statement
 lblGrossPay.text = Val(txtHoursWorked.text) * Val(txtPayRate.text)
▪ Gets data from txtHoursWorked.text and txtPayRate.text
▪ Assigns results from hours * rate calculation to lblGrossPay.text
 Val changes the text input from the text box into a number
 btnExit
 Button Click Event
 End
3 Major Types of Errors
 Syntax Errors – Language Errors
 Caught by the Compiler & Interpreter
 Visual Basic – wavy line under problem code
 Run-Time Errors
 Program will not run to normal completion
 Program Crashes
 Logic Errors
 Program Runs but produces incorrect results

Attempt to run the application - find syntax
errors and runtime errors
 Correct any syntax errors found – indicated by wavy
blue line
 All syntax errors must be removed before Visual
Basic will create a program that actually runs
 Find and correct and correct any runtime errors
until program runs to normal completion

Run the application using test data as input
 Run the program with a variety of test data
 Must test for expected and unexpected input
▪ negative numbers, blank text box, etc.
▪ will talk about how to deal with invalid input later
 Check the results to be sure that they are correct
 Correct any logic errors found
 Repeat this step as many times as necessary
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Homework 2
 Visual Basic Application
 See handout for details and due date
 Questions?