Class Notes 6/7/06

 

Today’s Menu:
Chapter 3
* Loop (go over and over)

2.a  grosspay

2.b netpay

Version of your payroll program.

Note: Specification is very important in programming and you need to follow the specification.

LOOP AS LABOR FORCE

One of the strengths of the computer is its ability to repeat a process over and over without getting tired of threatening to strike. The program that you have written to perform a single task can now be repeated to perform the same task as many times as you wish. This process of going over and over is known as repetition and is called a loop.  Can you think of a loop? Of course! Our everyday activities, including getting up, eating, working, studying and sleeping are examples of a loop. Can you identify other loops?

COMPUTERS IN THE LOOP

Did you know that your computer is in a constant cycle of input, process, and output? This constant cycle of input, processing and output means that your computer is in a loop. It waits for you to enter data, takes your input, analyzes it, performs the required task, and finally displays the result. We can generalize and say that every automated system, from the bank ATM machine, supermarket pricing, through the search engine of the internet all use the loop.

Example of while loop.

Want to run while 5 times then end  it with end while.

While (5)

Id = inputbox (“Enter ID”)

Msgbox(“Your ID is ” & ID)

End while

If you don’t want to use msgbox bye bye. The we will use brasses 

Msgbox(“BYE BYE”)

Conclusion:
While loop has a condition, if condition is true, loop will execute, if it’s false, loop won’t execute.
Example: 2>5 (False) , 2>3 (False), 3>2 (True)
Make a conditional loop.

See examples on page (57)

Version 1: counter = 5, while (counter)

Dim counter As Integer

counter =5

while (counter)

msgbox(“I LIKE YOU”)

counter = counter -1

end while

msgbox(“BYE BYE LOVE”)
NOTE: This program executes 5 times displaying the message “I LOVE YOU”, then it displays the message “BYE BYE LOVE”

Version 2: counter = 5, while (counter > 0)

Dim counter As Integer

        counter = 5

        While (counter > 0)

            MsgBox("I LIKE YOU")

            counter = counter - 1

        End While

        MsgBox("BYE BYE LOVE")

This program does the same thing, but in another way.

Version 3: same example with counter = 0

Dim counter As Integer

        counter = 0

        While (counter < 5)

            MsgBox("I LIKE YOU")

            counter = counter + 1

        End While

        MsgBox("BYE BYE LOVE")

Assignment on page 89, code on page 61

3a) Expand your Payroll program so that interactively repeats for 5 employees.

  Dim employeeid, hoursworked, counter As Integer

        Dim hourlyrate, grosspay As Double

counter = 5

        While (counter = 5)

            employeeid = InputBox("ENTER ITEM ID")

            hoursworked = InputBox("ENTER HOURS WORKED")

            hourlyrate = InputBox("ENTER HOURLY RATE")

            grosspay = hoursworked * hourlyrate

            MsgBox("EMPLOYEE ID IS " & employeeid)

            MsgBox("YOUR GROSS PAY IS " & grosspay)

counter = counter - 1

        End While

        MsgBox("BYE BYE")

Another version using textbox

IT ONLY DISPLAYS THE LAST DATA ENTERED

Dim employeeid, hoursworked, counter As Integer

        Dim hourlyrate, grosspay, taxamount, netpay As Double

        counter = 5

        While (counter)

            employeeid = InputBox("ENTER ITEM ID")

            hoursworked = InputBox("ENTER HOURS WORKED")

            hourlyrate = InputBox("ENTER HOURLY RATE")

            textbox1.text = employeeid

            textbox2.text = hoursworked

            TextBox3.Text = hourlyrate

            grosspay = hoursworked * hourlyrate

            textbox4.text = grosspay

            counter = counter - 1

        End While

        MsgBox("BYE BYE")

Version 3 OF CHAP 2. NOT USING LOOP BUT USING BUTTONS AND TXTBOX

By typing TextBox1.Text = " " we assign a blank value to the textbox

 

 Dim employeeid, hoursworked As Integer

        Dim hourlyrate, grosspay As Double

        employeeid = TextBox1.Text

        hoursworked = TextBox2.Text

        hourlyrate = TextBox3.Text

        grosspay = hoursworked * hourlyrate

        TextBox4.Text = grosspay

    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click

        TextBox1.Text = " "

        TextBox2.Text = " "

        TextBox3.Text = " "

     TextBox4.Text = " "