Create a VB application for the following Math Application. <?xml:namespace pref
ID: 3553660 • Letter: C
Question
Create a VB application for the following Math Application. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /?>
This application is for the first and second grade students to practice adding, subtracting and multiplying numbers. The application should display the addition, subtraction or multiplication problem on the screen, then allow the student to enter the answer, and then verify that the answer is correct. If the student's answer is not correct, the application should give him or her as many chances as necessary to answer the problem correctly.
The problems displayed for the students into two levels. The first grade students should use numbers from 1 through 10 only; the problems for the second grade students should use numbers from 10 through 1000. This application also wants to keep track of how many correct and incorrect responses the student makes.
To be a more robust application, please include exception-handlers for preventing different kinds of run-time errors.
Explanation / Answer
the code for creating random numbers:
static void Main(string[] args)
{
int[] randomNum = new int[1000];
Random RandomNumber = new Random();
for ( int i = 0; i<1000; i++)
{
randomNum[i] = RandomNumber.Next(1, 1000);
}
foreach (int j in randomNum)
{
Console.WriteLine("First Number:{0}", j);
}
Console.Read();
DETAILED EXPLANATION ALONG WITH CODE:
The calculator will have the following functionality:
Addition
Subtraction
Division
Multiplication
Square Root
Exponents (Power Of)
Clear Entry
Clear All
There will be a 2nd tutorial that will cover some more advanced features such as
Adding a number to memory
Removing a number from memory
Calculating with a number in memory
Entering numbers by typing
The first thing you need to do is create a new project in Visual Studio (or Visual Basic Express Edition if thats what you use). Once you have created your new project you need to create your user interface, your user interface should look like this:
Attached Image
Your user interface will consist of
Buttons 0 through 9
Buttons for
Addition
Subtraction
Division
Multiplication
Exponents (x^)
Inverse (1/x)
Square Root (sqrt)
Decimal
Equals
Backspace
CE (Clear Entry)
C (Clear All)
ReadOnly TextBox for input (Make sure TabStop is also set to False)
How you setup your user interface is up to you, but remember people are used to a calculator looking a certain way so you may wish to follow my example.
In this tutorial I will show you how to code two of the number buttons (since all 10 are the same except the zero button), how to code the calculations buttons, the clear buttons and the backspace buttons. Before writing any code you need to add the following variables to the top (Globals):
01
'variables to hold operands
02
Private valHolder1 As Double
03
Private valHolder2 As Double
04
'Varible to hold temporary values
05
Private tmpValue As Double
06
'True if "." is use else false
07
Private hasDecimal As Boolean
08
Private inputStatus As Boolean
09
Private clearText As Boolean
10
'variable to hold Operater
11
Private calcFunc As String
These variables will be used through out our program thats why they're globals. Now, before any calculations can be done, the user needs to be able to enter numbers into the input box, so lets take a look at how to do that (Ill use the number 1 key and the zero key).
Number one key:
01
Private Sub cmd1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd1.Click
02
'Check the inputStatus
03
If inputStatus Then 'Its True
04
'Append values to the value
05
'in the input box
06
txtInput.Text += cmd1.Text
07
Else 'Value is False
08
'Set the value to the value of the button
09
txtInput.Text = cmd1.Text
10
'Toggle inputStatus to True
11
inputStatus = True
12
End If
13
End Sub
When a user clicks a number button (in this case the number one button) we check the status of the inputStatus flag. If its true then we know we can just append the next value to the end of whats currently in the input box, otherwise we just enter the number into the input box. All the remaining numbers follow this procedure, except the zero button, this one is slightly different as we don't want the user to be able to enter zero as the first number (this is covered more in the decimal button functionality).
So lets take a look at how we code the zero button:
01
Private Sub cmd0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd0.Click
02
'Check the input status
03
If inputStatus Then 'If true
04
'Now check to make sure our
05
'input box has a value
06
If txtInput.Text.Length >= 1 Then
07
'Add our zero
08
txtInput.Text += cmd0.Text
09
End If
10
End If
11
End Sub
First we check the status of the inputStatus flag, if its true we know we can enter a number in the box. Here we do a second check, we make sure the length of the text in the input box is at least 1 (it has a value), if so we enter the zero into the input box.
For adding a decimal to our input box we need to first make sure our input box doesn't already contain one, then we need to make sure our input box has a value (don't want the user to be able to enter a decimal as the first value). Then we make sure the value in the input area isn't 0 (zero), this we will handle later.
If all those are true then we enter the decimal then toggle the hasDecimal to True, so the user cant enter a 2nd one. Now, if the input area doesn't have a value, we enter 0., as we assume the user is wanting to work with a decimal value such as 0.5. Lets take a look at the procedure for doing this:
01
Private Sub cmdDecimal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdDecimal.Click
02
'Check for input status (we want true)
03
If inputStatus Then
04
'Check if it already has a decimal (if it does then do nothing)
05
If Not hasDecimal Then
06
'Check to make sure the length is > than 1
07
'Dont want user to add decimal as first character
08
If txtInput.Text.Length > 1 Then
09
'Make sure 0 isnt the first number
10
If Not txtInput.Text = "0" Then
11
'It met all our requirements so add the zero
12
txtInput.Text += cmdDecimal.Text
13
'Toggle the flag to true (only 1 decimal per calculation)
14
hasDecimal = True
15
End If
16
Else
17
'Since the length isnt > 1
18
'make the text 0.
19
txtInput.Text = "0."
20
End If
21
End If
22
End If
23
End Sub
As you can see, we check all the items mentioned above, if they're True we add the decimal, otherwise we add 0. to the input area.
Next we want to be able to add numbers together. The first thing we do here is to make sure the input box has a value (Length > 1). If it does then we check the calcFunc value. The calcFunction variable will be used to tell our CalculateTotals procedure which calculation to perform. Here, if the value is empty (String.Empty) we assign the value of our input box to a variable, valHolder1, which will hold the first part of all calculations, then clear out the input box so the user can enter a 2nd number.
If the calcFunc variable isnt empty then we call our CalculateTotals procedure to display a total to the user. We then assign the value of Add to our variable for the next turn through, then we toggle the bb]hasDecimal[/b] flag to False.
Now lets take a look at how we accomplished this:
01
Private Sub cmdAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAdd.Click
02
'Make sure out input box has a value
03
If txtInput.Text.Length <> 0 Then
04
'Check the value of our function flag
05
If calcFunc = String.Empty Then 'Flag is empty
06
'Assign the value in our input
07
'box to our holder
08
valHolder1 = CType(txtInput.Text, Double)
09
'Empty the input box
10
txtInput.Text = String.Empty
11
Else 'Flag isnt empty
12
'Call our calculate totals method
13
CalculateTotals()
14
End If
15
'Assign a value to our calc function flag
16
calcFunc = "Add"
17
'Toggle the decimal flag
18
hasDecimal = False
19
End If
20
End Sub
Believe it or not, all the other basic calculation buttons are the same as the Add button, with the exception of what we set calcFunc to. In the other buttons we set this variable to the calculation we want to perform, Subtract,
Divide, Multiply, and so on, so there really isn't a reason to show how that is done since we did the Add button and the others are the same.
Lets say you want to give the user the option to calculation Exponents, 4^2 for example. To code this button you need a couple of checks before doing anything. First we need to check and make sure the input area has a value, if it does then we check to see the value of the calcFunc variable.
If this is empty, we then convert the value of the input area to a Double and assign it to the valHolder1 variable to hold on to, this will be used for the calculations in the CalculateTotals procedure and empth the value from the input area.. If its not empty we directly call the CalculateTotals function as this means the user has already entered 2 numbers.
We then assign the value of PowerOf to our calcFunc variable, this will tell CalculateTotals what calculation to perform, and toggle the hasDecimal flag to False.
Lets take a look at how we accomplished all of this:
01
Private Sub cmdPowerOf_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPowerOf.Click
02
'Make sure the input box has a value
03
If txtInput.Text.Length <> 0 Then
04
'Check if the calcFunc flag is empty
05
If calcFunc = String.Empty Then
06
'Assign the value of the input box to our variable
07
valHolder1 = CType(txtInput.Text, Double)
08
'Empty the input box
09
'So the user can enter the power of value
10
txtInput.Text = String.Empty
11
Else
12
'Call the calculate totals method
13
CalculateTotals()
14
End If
15
'Assign our flag the value of "PowerOf"
16
calcFunc = "PowerOf"
17
'Reset the decimal flag
18
hasDecimal = False
19
End If
20
End Sub
Doing a Square Root is somewhat different as it doesn't take 2 values, just the number you want the square root of, so some of the checking required in the other calculations isn't required here. For a Square Root we first check to ensure the input area has a value. If it does have a value we assign the value of the input area, converted to a Double, to our tmpValue variable.
Once we have the value, we call the System.Math.Sqrt Method to perform the calculations on the tmpValue variable. Once this is complete we assign the resulting value to our input area, then toggle the hasDecimal flag to False.
Lets take a look at how this is done:
01
Private Sub cmdSqrRoot_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSqrRoot.Click
02
'Make sure the input box has a value
03
If txtInput.Text.Length <> 0 Then
04
'Assign our variable the value in the input box
05
tmpValue = CType(txtInput.Text, Double)
06
'Perform the square root
07
tmpValue = System.Math.Sqrt(tmpValue)
08
'Display the results in the input box
09
txtInput.Text = CType(tmpValue, String)
10
'Clear the decimal flag
11
hasDecimal = False
12
End If
13
End Sub
The Equals button is quite simple. Here, we first check to make sure our input area has a value and that our valHolder1 variable isn't a zero (Divide by 0 is a bad thing). If both of these are true we call the CalculateTotals procedure to perform our calculations based on the value of the calcFunc flag. We then clear the value of calcFunc and toggle the hasDecimal flag to False. This is done like this:
01
Private Sub cmdEqual_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdEqual.Click
02
'Make sure theres a value in the input box
03
'And that our temp value isnt 0
04
If txtInput.Text.Length <> 0 AndAlso valHolder1 <> 0 Then
05
'Call the calculate totals method
06
CalculateTotals()
07
'Clear the calcFunction value
08
calcFunc = String.Empty
09
'Toggle the decimal flag
10
hasDecimal = False
11
End If
12
End Sub
We have 3 more buttons to look at before we look at the CalculateTotals procedure. First we'll look at the backspace button.For the backspace, first we need to make sure the input are has a value. If it does then we retrieve the next to last character and see if its a decimal, if it is we toggle the hasDecimal flag to False. Next we create an Integer variable (loc) to hold the length of the contents in the input area. From there we use Remove, along with loc to remove the last character of the string for each time the user clicks the backspace button.
01
Private Sub cmdBackspace_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBackspace.Click
02
'Declare locals needed
03
Dim str As String
04
Dim loc As Integer
05
'Make sure the text length is > 1
06
If txtInput.Text.Length > 0 Then
07
'Get the next to last character
08
str = txtInput.Text.Chars(txtInput.Text.Length - 1)
09
'Check if its a decimal
10
If str = "." Then
11
'If it is toggle the hasDecimal flag
12
hasDecimal = False
13
End If
14
'Get the length of the string
15
loc = txtInput.Text.Length
16
'Remove the last character, incrementing by 1
17
txtInput.Text = txtInput.Text.Remove(loc - 1, 1)
18
End If
19
End Sub
The last 2 buttons I'm going to demonstrate are the CE (Clear entry) and C (Clear all) buttons. These are very simple. First the clear entry button. What we do here is set the value in the input area to empty (String.Empty), and the hasDecimal flag to false.
1
Private Sub cmdClearEntry_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClearEntry.Click
2
'Empty the input box
3
txtInput.Text = String.Empty
4
'Toggle the decimal flag
5
hasDecimal = False
6
End Sub
The clear all button required a bit more code as we do more with this button. Here we set our 2 holder variables, valHolder1 and valHolder2 to 0 (zero), we then set the calcFunc flag to String.Empty and the hasDecimal flag to False, like this:
01
Private Sub cmdClearAll_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClearAll.Click
02
'Empty the text in the input box
03
txtInput.Text = String.Empty
04
'Clear out both temp values
05
valHolder1 = 0
06
valHolder2 = 0
07
'Set the calc switch to empty
08
calcFunc = String.Empty
09
'Toggle the hasDecimal flag
10
hasDecimal = False
11
End Sub
Those are the buttons you need for a Basic calculator. The final thing we're going to look at is the procedure that actually does the calculations, CalculateTotals. Here the first thing we do is set our variable valHolder2 to the current value of the input area. We then do a Select Case on the value of calcFunc so we know which calculations to perform. We perform our calculations (add, subtract, divide, multiply, exponent, etc) and set the results to the input area so the user can see their results. Finally we set the inputEntry flag to False. THis iw hat this procedure looks like:
01
Private Sub CalculateTotals()
02
valHolder2 = CType(txtInput.Text, Double)
03
Select Case calcFunc
04
Case "Add"
05
valHolder1 = valHolder1 + valHolder2
06
Case "Subtract"
07
valHolder1 = valHolder1 - valHolder2
08
Case "Divide"
09
valHolder1 = valHolder1 / valHolder2
10
Case "Multiply"
11
valHolder1 = valHolder1 * valHolder2
12
Case "PowerOf"
13
valHolder1 = System.Math.Pow(valHolder1, valHolder2)
14
End Select
15
txtInput.Text = CType(valHolder1, String)
16
inputStatus = False
17
End Sub