HELP ASAP!! Infinite Loop? (VB.NET)

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I am writing a program that I think I am getting an infinite loop on. Can’t seem to figure out where. I am sure it is more than likely the first loop being done. Anyway so you know what I am trying to do. I am asking for someone to enter an amount they are “depositing” into an account that is compiled annually by an interest also provided by the user. From that information I am to determine how long it will take for that initial amount of money to double and how long it is to take to make a million dollars. Every time I run the program it freezes up on me any help provided is much appreciated. Here is my code.

    Private Sub btnDetermine_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDetermine.Click

        'Declare Variables
        Dim balance, r As Double
        Dim numYearsMil As Integer
        Dim numYearsDoub As Integer

        'Get initial value of balance, and rate from a textbox
        balance = CDbl(txtAmount.Text)
        r = CDbl(txtRate.Text)

        'Loop determines the number of years it will take to double your money
        Do While balance = (balance * 2)

        'Prints the number of years it takes to double your money
        txtDouble.Text = "in " & numYearsDoub & " years you will double your money."

        'Loop determins the number of years it will take to become a millionare
        Do While balance < 1000000

            balance += r * balance
            numYearsMil += 1

        Loop

        'Prints the number of years it takes to become a millionare
        txtMillion.Text = "In " & numYearsMil & " years you will have a million dollars."

    End Sub

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Ok I’ve narrowed down the problem. It is in the first Do Loop. For some reason the doubleing money is holding up the system. Without that I can easily get the number of years it takes to make a million. But if that loop is there then it bogs up the system and gives me odd numbers. I don’t know what to do with it. Oh I took out the = sign in the first loop and it stoped freezing on me.

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Ok I’ve narrowed down the problem. It is in the first Do Loop. For some reason the doubleing money is holding up the system. Without that I can easily get the number of years it takes to make a million. But if that loop is there then it bogs up the system and gives me odd numbers. I don’t know what to do with it. Oh I took out the = sign in the first loop and it stoped freezing on me.

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Narrowed the problem to one line. Some where in the Do Loop statement it is messing up. WHen I get the number calc it is saying something like 11984 for the number of years to double. Ok so then if I have the loop statement like this

Do While balance < (balance * 2)
balance = (r + 1) * balance
numYearsDoub += 1
Loop

where is it wrong? I know it is the Do While balance < (balance * 2) but I can't figure out why that is the problem. Any help is appreciated.

Here is updated code.

Private Sub btnDetermine_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDetermine.Click

        'Declare Variables
        Dim balance, r, amount As Double
        Dim numYearsMil, numYearsDoub As Integer

        'Get initial value of balance, and rate from a textbox
        balance = CDbl(txtAmount.Text)
        amount = CDbl(txtAmount.Text)
        r = CDbl(txtRate.Text)

        Do While amount < amount * 2

            amount = (1 + r) * amount
            numYearsDoub += 1

        Loop

        'Loop determines the number of years it will take to double your money
        Do While balance < 1000000

            balance = (1 + r) * balance
            numYearsMil += 1

        Loop

        'Prints the number of years it takes to become a millionare
        txtDouble.Text = "In " & numYearsDoub & " years you will double your money."
        txtMillion.Text = "In " & numYearsMil & " years you will have a million dollars."

    End Sub

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Won’t x always be less than x * 2 ? Until you overflow the maximum size of a “double”… I think you want the comparison on the right to refer to something like CDbl(txtAmount.Text) * 2 rather than using the variable you are changing inside the loop.

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You could set up a variable like dblBaseAmount = CDbl(txtAmount.Text) then set amount and balance = to it and use do while amount < BaseAmount * 2 in the first loop

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Thanks for the tips I ended up figuring it out. When I get home I will post the code if needed.

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Thanks for the tips I ended up figuring it out. When I get home I will post the code if needed.

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You could set up a variable like dblBaseAmount = CDbl(txtAmount.Text) then set amount and balance = to it and use do while amount < BaseAmount * 2 in the first loop

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Won’t x always be less than x * 2 ? Until you overflow the maximum size of a “double”… I think you want the comparison on the right to refer to something like CDbl(txtAmount.Text) * 2 rather than using the variable you are changing inside the loop.

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Narrowed the problem to one line. Some where in the Do Loop statement it is messing up. WHen I get the number calc it is saying something like 11984 for the number of years to double. Ok so then if I have the loop statement like this

Do While balance < (balance * 2)
balance = (r + 1) * balance
numYearsDoub += 1
Loop

where is it wrong? I know it is the Do While balance < (balance * 2) but I can't figure out why that is the problem. Any help is appreciated.

Here is updated code.

Private Sub btnDetermine_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDetermine.Click

        'Declare Variables
        Dim balance, r, amount As Double
        Dim numYearsMil, numYearsDoub As Integer

        'Get initial value of balance, and rate from a textbox
        balance = CDbl(txtAmount.Text)
        amount = CDbl(txtAmount.Text)
        r = CDbl(txtRate.Text)

        Do While amount < amount * 2

            amount = (1 + r) * amount
            numYearsDoub += 1

        Loop

        'Loop determines the number of years it will take to double your money
        Do While balance < 1000000

            balance = (1 + r) * balance
            numYearsMil += 1

        Loop

        'Prints the number of years it takes to become a millionare
        txtDouble.Text = "In " & numYearsDoub & " years you will double your money."
        txtMillion.Text = "In " & numYearsMil & " years you will have a million dollars."

    End Sub

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