C#

    if (purchased >= 100)
    {
        discountrate = FIFTY_PCT_double;
    }
    //if the purchased units are greater than or equal to 50,               
    //but less than or equal to 99, put 40% in the first label
    else if (purchased >= 50)
    {
        discountrate = FORTY_PCT_double;

    }
    //if the purchased units are greater than or equal to 20, 
    //or less than or equal to 49, use 30% in the first label
    else if (purchased >= 20)
    {
        discountrate = THIRTY_PCT_double;

    }
    //if the purchased amount is less than or equal to 19 
    //or greater than or equal to 10, use %20 in the first label
    else if (purchased >= 10)
    {
        discountrate = TWENTY_PCT_double;
    }
    //if the purchased amount is between 0 and 10 or equal, the discount is 0%
    else
    {
        discountrate = ZERO_PCT_double;

    }
    saved = (purchased * PACKAGE_COST_double) * discountrate;
    retail = purchased * PACKAGE_COST_double;
    total = retail - saved;

    discountLabel.Text = string.Format("{0}%", discountrate * 100);
    totalLabel.Text = total.ToString("c"); 
    total = retail - saved;
    retail = purchased * PACKAGE_COST_double;
    savedLabel.Text = saved.ToString("c");
}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}

namespace Software_Sales
{
    public partial class salesForm : Form
    {
        public salesForm()
        {
            InitializeComponent();
        }

        private void calculateButton_Click(object sender, EventArgs e)
        {
            //declaring the amount each unit costs
            const double PACKAGE_COST_double = 99;

            //declaring the discount rate variables
            const double FIFTY_PCT_double = .5;
            const double FORTY_PCT_double = .4;
            const double THIRTY_PCT_double = .3;
            const double TWENTY_PCT_double = .2;
            const double ZERO_PCT_double = 0;

            
            double retail;  //holds the cost without any discount
            double discountrate; 
            double saved;        //to hold the amount saved
            double total;        //to hold the total after discount
            int purchased;    //to hold the purchased units   

            purchased = int.Parse(purchasedTextBox.Text);
            

            //calculate the data from purchasedTextBox
            try
            {
                //get the # of purchased units
                purchased = int.Parse(purchasedTextBox.Text);

                //if the purchased units are greater than or equal to 100,
                //put 50% in the first label
                if (purchased >= 100)
                {
                    discountrate = FIFTY_PCT_double;

                }
                //if the purchased units are greater than or equal to 50,               
                //but less than or equal to 99, put 40% in the first label
                else if (purchased >= 50)
                {
                    discountrate = FORTY_PCT_double;

                }
                //if the purchased units are greater than or equal to 20, 
                //or less than or equal to 49, use 30% in the first label
                else if (purchased >= 20)
                {
                    discountrate = THIRTY_PCT_double;

                }
                //if the purchased amount is less than or equal to 19 
                //or greater than or equal to 10, use %20 in the first label
                else if (purchased >= 10)
                {
                    discountrate = TWENTY_PCT_double;

                }
                //if the purchased amount is between 0 and 10 or equal, the discount is 0%
                else
                {
                    discountrate = ZERO_PCT_double;
                }

                retail = purchased * PACKAGE_COST_double;
                saved = (purchased * PACKAGE_COST_double) * discountrate;
                total = retail - saved;

                discountLabel.Text = string.Format("{0}%", discountrate * 100);
                totalLabel.Text = total.ToString("c");        
                savedLabel.Text = saved.ToString("c");

                
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}

struct TransactionResult
{   
    double amount;
    bool Success;
    int ErrorCode;
}

Frygreen wrote:

b) returning some additional information requires to return a object with additional attributes or a reference to an object in the parameterlist. Seems to be crazy too.

Frygreen wrote:

a) throwing an exception could be wrong, because this scenario is not "exceptional", but standard

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

public decimal MakeWithdraw(ref decimal balance, decimal amount, bool allowOverdraft=false)
{
    decimal widthdrawn = (amount <= balance) ? amount : ((allowOverdraft) ? amount : balance);
    balance -= withdrawn;
    return widthdrawn;
}

struct TransactionResult {   
    double amountReturned;
    EnumTransactionResult eReturn;
}