This is an open-book test. You may use the text book Be Sharp with C# but no other sources, written or electronic, will be allowed.

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1 UNIVERSITY OF THE FREE STATE DEPARTMENT OF COMPUTER SCIENCE AND INFORMATICS RIS 124 DATE: 5 September 2011 TIME: 3½ hours MARKS: 150 ASSESSORS: Prof. P.J. Blignaut & Mr. M.B. Mase MODERATOR: Dr. A. van Biljon This is an open-book test. You may use the text book Be Sharp with C# but no other sources, written or electronic, will be allowed. Answer the following question on paper. Question 1 (30 minutes) Consider the following class definition for a mortgage loan: SECTION A class CMortgage public decimal LoanAmount get; set; public int Term get; set; public double Rate get; set; 1.1 The monthly payment on a mortgage loan can be calculated according to the formula: M = P(i(1+i) n )/((1+i) n 1) where P = mortgage amount i = Monthly interest rate as fraction, e.g for 1%. n is the term in months. Add a method to the class that will return the monthly payment. (6) 1.2 As the class is defined at the moment, the user is expected to enter the monthly interest rate as a fraction. This means that the class user will have to divide the percentage annual interest rate by 1200 before it can be assigned to the property. Add a private data member for the monthly rate to the class and change the property so that the user will be allowed to enter the interest rate as percentage per year. (4) 1.3 Consider the following implementation of the class in a console application. Complete the missing parts. (9) static void Main(string[] args) //1.3.1 Declare and instantiate Mortgage object... //1.3.2 Read loan amount from keyboard and assign to // LoanAmount property Console.Write("Loan amount : ");... //1.3.3 Read percentage annual interest rate from keyboard and // assign to Rate property Console.Write("Interest rate (% per year) : ");... //1.3.4 Read the term (months) from keyboard and assign to // Term property Console.Write("Term (months) : ");...

2 //1.3.5 Display output Console.WriteLine("Monthly payment : 0:C",...); 2 //Allow user opportunity to read the output Console.WriteLine(); Console.Write("Press any key to exit..."); Console.ReadKey(); 1.4 Change the class definition so that it would not be possible to instantiate objects of the class. (1) 1.5 Add a public abstract method, LumpSumPayment to CMortgage that will allow the user to make a lump sum payment. The method must take a single decimal parameter with the amount that will be paid. The method will not return any value. (3) 1.6 Create a new class, CHomeLoan that will inherit from CMortgage. (2) 1.7 In CHomeLoan, override the method LumpSumPayment of the base class. The method must subtract the paid amount from the loan amount. (3) [28] SECTION B Answer any two of the following three questions by developing the solutions in C#. Make sure that you enter your name, student number and question number for every class in a comment block at the top of the code window. You will not get marks if you do it, but you will lose 3 marks for every question if you don t do it. You might even get zero for the entire test if you don t do it! Make sure that you give appropriate names to all controls and variables. Create a folder on the T-drive in the format Surname_StudentNumber, e.g. Blignaut_ Create all projects, one for each question, in this folder. Question 2 (30 minutes) Develop a Windows forms application as in the example that will allow the user to enter a sentence and then count the number of words in the sentence. You may not use the method Split(). Hint: You can count the words by counting the transitions from space to no-space. [20] Question 3 (30 minutes) Develop a console application that will do a compile-time initialisation and put the following integers in this order in a one-dimensional array, Numbers: 13, 7, 99, 52, 88, 41, 56, 78, 101, 66. Call two methods. The first method should take the array, Numbers, as parameter and return the square roots of the numbers as another array. The second method should return void and take both the original numbers and the square roots as two parallel arrays as parameters and display the original array along with the square roots as in the screen print below. The Main() method of the program is given below, with some parts removed which you must complete:

3 static void Main(string[] args) //Compile-time initialisation of array int[] Numbers =... //Sort the numbers... //Get the square roots double [] SquareRoots = GetSquareRoots(Numbers); //Display the numbers along with the square roots DisplayNumbers(Numbers, SquareRoots); 3 //Allow the user time to read the output Console.Write("\n\n\nPress any key to exit..."); Console.ReadKey(); [20] Question 4 (30 minutes) Consider the scenario of a queue of people waiting to be helped at a counter. This is a typical example of the first-in-first-out principle where the person at the front of the queue is always helped first and the ones coming later are added to the back of the queue. Develop an application that will allow a user to add the names of people to a list box as they arrive at the door. When the first person in the list is helped, his name must be removed from the list, meaning that all the others will move one place up. For some reason or other, a clerical worker in the office needs to list all the people in the queue in alphabetical order. The first person in the queue should not lose his position, even though his name does not appear at the top of the list anymore. 4.1 Develop the form as in the example. 4.2 Declare an array list on form level that will be used to store the names of the people in the queue. Instantiate the array list in the form s constructor. 4.3 Write the click event handler for the Add button. (i) Enter the name of the person (as entered by the user in the text box above) to the list box. (ii) Add the name of the person to the array list. (iii) Clear the text box and put the cursor back in the text box. 4.4 Sort the items in the list box in the click event handler of the Sort button. 4.5 Write the click event handler for the Original order button. Step through the array list and refill the list box. 4.6 Write the click event handler for the Remove first person button. Hint: Sort the people in the queue in the original order first, then remove the first person in both arrays and then sort the list box again if it was sorted before. [20]

4 4 SECTION C Question 5 (90 minutes) Develop an object oriented GUI application that will assist a stock manager to keep track of his stock. There are two types of stock: Capital and consumables. All stock items have a stock code and description. Capital items also have an asset number while the quantity of consumables on hand should be saved. Allow the user to enter several stock items one after the other in any order. When the user clicks on New, all data fields should be cleared to prepare input for a new item. For capital items the Asset number field must be visible and for consumables the Quantity on hand item must be available. A list of items in stock should be available at any time. A possible interface is shown below. 5.1 Develop the class CStock. It must not be possible to instantiate objects of CStock. Declare auto-implemented properties for the StockCode and Description. Besides the basic constructor, make also provision for a constructor that will have parameters with which the stock code and description can be initialised. (11) 5.2 Develop the class CConsumable to inherit from CStock. Declare an auto-implemented property for the quantity on hand. The basic constructor must assign a 0 to this property and a second constructor must use a parameter to initialise the property. (8) 5.3 Develop the class for CCapitalItem to inherit from CStock. Declare an auto-implemented property for the asset number. The basic constructor must assign an empty string to this property and a second constructor must use parameters to initialise all properties in the sub-class and base class. (12) 5.4 Develop the form as in the example above. Note that there is another button Save underneath New. Only one of these two buttons, New and Save, is visible at a time. (4) 5.5 Write the code for the click event handler of the Close button. (1) 5.6 Write code for the CheckedChanged event handlers of the two radio buttons that will set visibility of the labels and text boxes for asset number and quantity on hand as necessary. (5) 5.7 Declare an array list, Stock, on form level and instantiate the array list in the form s Load event handler. This array list will be used to store individual instances of either CConsumable or CCapitalItem. (2) 5.8 Write a method, ClearControls(), to clear all text boxes and uncheck all radio buttons. Put the focus in the text box for stock code. (9) 5.9 Write the code for the click event handler of the New button. Clear the controls, set the visibility of the New and Save buttons to false and true respectively and disable the buttons for List and Remove All. (5) 5.10 Write the code for the click event handler of the Save button. (i) Declare a local object, Item, of CStock. (1) (ii) Depending on which radio button is checked, instantiate Item to be either a CCapitalItem or CConsumable. If it is a CCapitalItem, use the constructor to assign values for the stock code, description and asset number. If it is a CConsumable, use the basic constructor and then assign values to the stock code, description and quantity on hand afterward. (8) (iii) Add the item to the list of stock items. (2) (iv) Set the visibility of the New and Save buttons to true and false respectively. (2) (v) Enable the buttons for List and Remove All. (2) 5.11 Write the code for the click event handler of the Remove all button. If the user confirms, all items must be removed from the array list. (4) 5.12 Write the code for the click event handler of the List button. Use a foreach to step through the array list and then display the stock in a message box as in the example. (9) [85]

5 5 MEMORANDUM Question public decimal Payment() return (decimal)((double)loanamount * (Rate * Math.Pow(1 + Rate, Term)) / (Math.Pow(1 + Rate, Term) - 1)); 1.2 private double drate; public double Rate get return drate; set drate = value / 1200; CMortgage Mortgage = new CHomeLoan(); Mortgage.LoanAmount = decimal.parse(console.readline()); Mortgage.Rate = double.parse(console.readline()); Mortgage.Term = int.parse(console.readline()); Console.WriteLine("Monthly payment : 0:C", Mortgage.Payment()); 1.4 abstract class CMortgage 1.5 public abstract void LumpSumPayment(decimal decamount); 1.6 class CHomeLoan : CMortgage 1.7 public override void LumpSumPayment(decimal decamount) LoanAmount -= decamount;

6 6 Question 2 Design of form File name of form, e.g. CfrmWords All components, excluding labels, have names private void Count1() //Add space to beginning string s = " " + txtsentence.text; //Declare variable int iwords = 0; //Step through characters of the string for (int i = 1; i < s.length; i++) if (s[i - 1] == ' ' && s[i]!= ' ') //Start of new word iwords++; //Display output string smsg = "Number of words : " + iwords.tostring(); MessageBox.Show(sMsg, "WORDS", OK, Info); Question 3 private void btncounts_click(object sender, EventArgs e) Count1(); private static double[] GetSquareRoots(int[] _Numbers ) double[] SquareRoots = new double [_Numbers.Length]; for (int i = 0; i < _Numbers.Length; i++) SquareRoots[i] = Math.Sqrt(_Numbers[i]); return SquareRoots; //GetSquareRoots static private void DisplayNumbers(int[] _Numbers, double[] _SquareRoots ) Console.WriteLine("Numbers\tSquare roots\n\n"); for (int i = 0; i < _Numbers.Length; i++) Console.WriteLine("0,5\t1,8:F3", _Numbers[i], _SquareRoots[i]); //DisplayNumbers static void Main(string[] args) int[] Numbers = 13, 7, 99, 52, 88, 41, 56, 78, 101, 66 ; Array.Sort(Numbers); double [] SquareRoots = GetSquareRoots(Numbers); DisplayNumbers(Numbers, SquareRoots); Console.Write("\n\n\nPress any key to exit..."); Console.ReadKey(); //Main

7 7 Question 4 (22) Design of form File name of form, e.g. CfrmQueue All components, excluding labels, have names public partial class CfrmQueue : Form ArrayList arrlstnames; public CfrmQueue() InitializeComponent(); arrlstnames = new ArrayList(); private void btnadd_click(object sender, EventArgs e) lstbxnames.items.add(txtname.text); arrlstnames.add(txtname.text); txtname.clear(); txtname.focus(); private void btnsort_click(object sender, EventArgs e) lstbxnames.sorted = true; private void SortOriginal() lstbxnames.sorted = false; lstbxnames.items.clear(); foreach (string sname in arrlstnames) lstbxnames.items.add(sname); private void btnoriginal_click(object sender, EventArgs e) SortOriginal(); private void btnremove_click(object sender, EventArgs e) if (lstbxnames.items.count > 0) bool issorted = lstbxnames.sorted; SortOriginal(); lstbxnames.items.removeat(0); arrlstnames.removeat(0); lstbxnames.sorted = issorted;

8 8 Question abstract class CStock public string StockCode get; set; public string Description get; set; public CStock() public CStock(string _sstockcode, string _sdescription ) StockCode = _sstockcode; Description = _sdescription; 5.2 class CConsumable : CStock public int QuantityOnHand get; set; public CConsumable() QuantityOnHand = 0; //CConsumable public CConsumable(int _iquantityonhand) QuantityOnHand = _iquantityonhand; //CConsumable 5.3 class CCapitalItem : CStock public string AssetNumber get; set; public CCapitalItem() AssetNumber = ""; public CCapitalItem(string _sstockcode, string _sdescription, string _sassetnumber ) StockCode = _sstockcode; Description = _sdescription; AssetNumber = _sassetnumber; 5.4 Design of form File name of form, e.g. CfrmStock All components, excluding labels, have names 5.5 private void btnclose_click(object sender, EventArgs e) this.close(); //btnclose_click

9 5.6 private void radcapital_checkedchanged(object sender, EventArgs e) lblassetnumber.visible = radcapital.checked; txtassetnumber.visible = radcapital.checked; lblquantityonhand.visible = radconsumable.checked; txtquantityonhand.visible = radconsumable.checked; //radcapital_checkedchanged Call this for both radio buttons. 5.7 ArrayList Stock; private void frmstock_load(object sender, EventArgs e) Stock = new ArrayList(); 5.8 private void ClearControls() txtstockcode.clear(); txtdescription.clear(); txtassetnumber.clear(); txtquantityonhand.text = "0"; radcapital.checked = false; radconsumable.checked = false; txtstockcode.focus(); //ClearControls 5.9 private void btnnew_click(object sender, EventArgs e) ClearControls(); btnnew.visible = false; btnsave.visible = true; btnlist.enabled = false; btnclearlist.enabled = false; private void btnsave_click(object sender, EventArgs e) CStock Item; if (radcapital.checked) Item = new CCapitalItem(txtStockCode.Text, txtdescription.text, txtassetnumber.text); else Item = new CConsumable(); Item.StockCode = txtstockcode.text; Item.Description = txtdescription.text; ((CConsumable)Item).QuantityOnHand = int.parse(txtquantityonhand.text); Stock.Add(Item); btnnew.visible = true; btnsave.visible = false; btnlist.enabled = true; btnclearlist.enabled = true;

10 5.11 private void btnclearlist_click(object sender, EventArgs e) if (MessageBox.Show("Sure you want to remove all items in stock?", "CONFIRM REMOVE", MessageBoxButtons.YesNo) == DialogResult.Yes) Stock.Clear(); //btnclearlist_click private void btnlist_click(object sender, EventArgs e) string s = "Code\tDescription\tAsset no/qty\n" + "====\t=========\t========\n\n"; foreach (CStock Item in Stock) s += Item.StockCode + "\t" + Item.Description; if (Item is CCapitalItem) s += "\t" + ((CCapitalItem)Item).AssetNumber + " (Capital item) \n"; else s += "\t" + ((CConsumable)Item).QuantityOnHand.ToString() + " (Consumable) \n"; MessageBox.Show(s, "Stock list"); //btnlist_click