- 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:
Your user interface will consist of
- Buttons 0 through 9
- Buttons for
- Exponents (x^)
- Inverse (1/x)
- Square Root (sqrt)
- 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):
'variables to hold operands Private valHolder1 As Double Private valHolder2 As Double 'Varible to hold temporary values Private tmpValue As Double 'True if "." is use else false Private hasDecimal As Boolean Private inputStatus As Boolean Private clearText As Boolean 'variable to hold Operater 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:
Private Sub cmd1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd1.Click 'Check the inputStatus If inputStatus Then 'Its True 'Append values to the value 'in the input box txtInput.Text += cmd1.Text Else 'Value is False 'Set the value to the value of the button txtInput.Text = cmd1.Text 'Toggle inputStatus to True inputStatus = True End If 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:
Private Sub cmd0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd0.Click 'Check the input status If inputStatus Then 'If true 'Now check to make sure our 'input box has a value If txtInput.Text.Length >= 1 Then 'Add our zero txtInput.Text += cmd0.Text End If End If 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:
Private Sub cmdDecimal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdDecimal.Click 'Check for input status (we want true) If inputStatus Then 'Check if it already has a decimal (if it does then do nothing) If Not hasDecimal Then 'Check to make sure the length is > than 1 'Dont want user to add decimal as first character If txtInput.Text.Length > 1 Then 'Make sure 0 isnt the first number If Not txtInput.Text = "0" Then 'It met all our requirements so add the zero txtInput.Text += cmdDecimal.Text 'Toggle the flag to true (only 1 decimal per calculation) hasDecimal = True End If Else 'Since the length isnt > 1 'make the text 0. txtInput.Text = "0." End If End If End If 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:
Private Sub cmdAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdAdd.Click 'Make sure out input box has a value If txtInput.Text.Length <> 0 Then 'Check the value of our function flag If calcFunc = String.Empty Then 'Flag is empty 'Assign the value in our input 'box to our holder valHolder1 = CType(txtInput.Text, Double) 'Empty the input box txtInput.Text = String.Empty Else 'Flag isnt empty 'Call our calculate totals method CalculateTotals() End If 'Assign a value to our calc function flag calcFunc = "Add" 'Toggle the decimal flag hasDecimal = False End If 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:
Private Sub cmdPowerOf_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPowerOf.Click 'Make sure the input box has a value If txtInput.Text.Length <> 0 Then 'Check if the calcFunc flag is empty If calcFunc = String.Empty Then 'Assign the value of the input box to our variable valHolder1 = CType(txtInput.Text, Double) 'Empty the input box 'So the user can enter the power of value txtInput.Text = String.Empty Else 'Call the calculate totals method CalculateTotals() End If 'Assign our flag the value of "PowerOf" calcFunc = "PowerOf" 'Reset the decimal flag hasDecimal = False End If 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:
Private Sub cmdSqrRoot_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSqrRoot.Click 'Make sure the input box has a value If txtInput.Text.Length <> 0 Then 'Assign our variable the value in the input box tmpValue = CType(txtInput.Text, Double) 'Perform the square root tmpValue = System.Math.Sqrt(tmpValue) 'Display the results in the input box txtInput.Text = CType(tmpValue, String) 'Clear the decimal flag hasDecimal = False End If 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:
Private Sub cmdEqual_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdEqual.Click 'Make sure theres a value in the input box 'And that our temp value isnt 0 If txtInput.Text.Length <> 0 AndAlso valHolder1 <> 0 Then 'Call the calculate totals method CalculateTotals() 'Clear the calcFunction value calcFunc = String.Empty 'Toggle the decimal flag hasDecimal = False End If 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.
Private Sub cmdBackspace_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdBackspace.Click 'Declare locals needed Dim str As String Dim loc As Integer 'Make sure the text length is > 1 If txtInput.Text.Length > 0 Then 'Get the next to last character str = txtInput.Text.Chars(txtInput.Text.Length - 1) 'Check if its a decimal If str = "." Then 'If it is toggle the hasDecimal flag hasDecimal = False End If 'Get the length of the string loc = txtInput.Text.Length 'Remove the last character, incrementing by 1 txtInput.Text = txtInput.Text.Remove(loc - 1, 1) End If 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.
Private Sub cmdClearEntry_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClearEntry.Click 'Empty the input box txtInput.Text = String.Empty 'Toggle the decimal flag hasDecimal = False 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:
Private Sub cmdClearAll_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClearAll.Click 'Empty the text in the input box txtInput.Text = String.Empty 'Clear out both temp values valHolder1 = 0 valHolder2 = 0 'Set the calc switch to empty calcFunc = String.Empty 'Toggle the hasDecimal flag hasDecimal = False 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:
Private Sub CalculateTotals() valHolder2 = CType(txtInput.Text, Double) Select Case calcFunc Case "Add" valHolder1 = valHolder1 + valHolder2 Case "Subtract" valHolder1 = valHolder1 - valHolder2 Case "Divide" valHolder1 = valHolder1 / valHolder2 Case "Multiply" valHolder1 = valHolder1 * valHolder2 Case "PowerOf" valHolder1 = System.Math.Pow(valHolder1, valHolder2) End Select txtInput.Text = CType(valHolder1, String) inputStatus = False End Sub
NOTE: For the Exponents (Power Of) we use the System.Math.Pow Method for calculating the value.
Thats it, thats how you create a basic calculator in VB.Net. I hope you find this tutorial helpful. I am including the project file with this tutorial, but remember this solution is under the GNU GENERAL PUBLIC LICENSE so you may not remove the header from the files or turn this project in as your homework assignment.
I know I am forced to go with the honor system in this, but if you do just turn this in as your assignment not only will you be cheating, but you will learn nothing, and subsequently wont know enough to become a programmer once you get out of school.
I will be doing a 2nd part to this tutorial where I look at adding more advanced functionality to this calculator, such
as adding a number to memory, removing a number from memory, calculations with a number in memory and more. Also, I will be creating a C# version of this calculator for the C# users.
Thank you for reading!
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