![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:
PrivateSubcmdAdd_Click(ByValsender AsSystem.Object, ByVale
01
AsSystem.EventArgs) HandlescmdAdd.Click
02 'Make sure out input box has a value
03 IftxtInput.Text.Length<> 0 Then
04 'Check the value of our function flag
05 IfcalcFunc = 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 EndIf
15 'Assign a value to our calc function flag
16 calcFunc = "Add"
17 'Toggle the decimal flag
18 hasDecimal = False
19 EndIf
20 EndSub
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](https://image.slidesharecdn.com/basiccalculatortutorial-130127214855-phpapp01/85/Basic-calculator-tutorial-5-320.jpg)
Basic calculator tutorial
- 1. Basic Calculator Tutorial In this tutorial, Basic Calculator in VB.Net, we will look at creating a basic calculator. 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:
- 2. Your user interface will consist of Buttons 0 through 9 Buttons for o Addition o Subtraction o Division o Multiplication o Exponents (x^) o Inverse (1/x) o Square Root (sqrt) Decimal Equals Backspace CE (Clear Entry) C (Clear All) ReadOnlyTextBox 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 PrivatevalHolder1 AsDouble 03 PrivatevalHolder2 AsDouble 04 'Varible to hold temporary values 05 PrivatetmpValue AsDouble 06 'True if "." is use else false 07 PrivatehasDecimal AsBoolean 08 PrivateinputStatus AsBoolean 09 PrivateclearText AsBoolean 'variable to hold 10 Operater
- 3. 11 PrivatecalcFunc AsString 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: PrivateSubcmd1_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) Handlescmd1.Click 02 'Check the inputStatus 03 IfinputStatus 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 EndIf 13 EndSub 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: PrivateSubcmd0_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) Handlescmd0.Click 02 'Check the input status 03 IfinputStatus Then'If true 04 'Now check to make sure our 05 'input box has a value 06 IftxtInput.Text.Length>= 1 Then 07 'Add our zero 08 txtInput.Text += cmd0.Text 09 EndIf 10 EndIf
- 4. 11 EndSub 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: PrivateSubcmdDecimal_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdDecimal.Click 02 'Check for input status (we want true) 03 IfinputStatus Then 04 'Check if it already has a decimal (if it does then do nothing) 05 IfNothasDecimal Then 06 'Check to make sure the length is > than 1 07 'Dont want user to add decimal as first character 08 IftxtInput.Text.Length> 1 Then 09 'Make sure 0 isnt the first number 10 IfNottxtInput.Text = "0"Then 11 'It met all our requirements so add the zero 12 txtInput.Text += cmdDecimal.Text 'Toggle the flag to true (only 1 decimal per 13 calculation) 14 hasDecimal = True 15 EndIf 16 Else 17 'Since the length isnt> 1 18 'make the text 0. 19 txtInput.Text = "0." 20 EndIf 21 EndIf 22 EndIf 23 EndSub As you can see, we check all the items mentioned above, if they're True we add the decimal,
- 5. 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: PrivateSubcmdAdd_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdAdd.Click 02 'Make sure out input box has a value 03 IftxtInput.Text.Length<> 0 Then 04 'Check the value of our function flag 05 IfcalcFunc = 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 EndIf 15 'Assign a value to our calc function flag 16 calcFunc = "Add" 17 'Toggle the decimal flag 18 hasDecimal = False 19 EndIf 20 EndSub 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
- 6. 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: PrivateSubcmdPowerOf_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdPowerOf.Click 02 'Make sure the input box has a value 03 IftxtInput.Text.Length<> 0 Then 04 'Check if the calcFunc flag is empty 05 IfcalcFunc = 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 EndIf 15 'Assign our flag the value of "PowerOf" 16 calcFunc = "PowerOf" 17 'Reset the decimal flag 18 hasDecimal = False 19 EndIf 20 EndSub 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.
- 7. Lets take a look at how this is done: PrivateSubcmdSqrRoot_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdSqrRoot.Click 02 'Make sure the input box has a value 03 IftxtInput.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 EndIf 13 EndSub 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: PrivateSubcmdEqual_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdEqual.Click 02 'Make sure theres a value in the input box 03 'And that our temp value isnt 0 04 IftxtInput.Text.Length<> 0 AndAlsovalHolder1 <> 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 EndIf 12 EndSub 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
- 8. 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. PrivateSubcmdBackspace_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdBackspace.Click 02 'Declare locals needed 03 Dimstr AsString 04 Dimloc AsInteger 05 'Make sure the text length is > 1 06 IftxtInput.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 Ifstr = "."Then 11 'If it is toggle the hasDecimal flag 12 hasDecimal = False 13 EndIf 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 EndIf 19 EndSub 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. PrivateSubcmdClearEntry_Click(ByValsender AsSystem.Object, ByVale 1 AsSystem.EventArgs) HandlescmdClearEntry.Click 2 'Empty the input box 3 txtInput.Text = String.Empty 4 'Toggle the decimal flag 5 hasDecimal = False 6 EndSub 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: PrivateSubcmdClearAll_Click(ByValsender AsSystem.Object, ByVale 01 AsSystem.EventArgs) HandlescmdClearAll.Click 02 'Empty the text in the input box
- 9. 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 EndSub 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. THisiw hat this procedure looks like: 01 PrivateSubCalculateTotals() 02 valHolder2 = CType(txtInput.Text, Double) 03 SelectCasecalcFunc 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 EndSelect 15 txtInput.Text = CType(valHolder1, String) 16 inputStatus = False 17 EndSub 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
- 10. 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!