Assignment 3 - Creating a Mental Arithmetic Testing Program

  Introduction

For twelve weeks of this course, we will be working step-by-step through assignment 3. This will familiarize you with the C++ language and concepts and give you practice in organizing the structure of a program.

You will need the assignment paper.

  The Assignment - Mental Arithmetic Tester

Briefly, the scenario is:-

To create mental arithmetic testing program. The program must be run in the command console and display a series of multiple choice questions. The user is given a final score and an opportunity to repeat the test or repeat only those questions incorrectly answered.

For the full scenario - please read the paper.

To see the program running, you may download my program executable if you wish.

  Step 1 - Welcome Message

When your program first starts, it should display a welcome screen.

1. Create a project and source code file. Call it something appropriate.

2. Include the library file iostream.h. Create a function called main.

3. Using cout, write code for displaying a welcome message on screen when your program starts. If you get a compiler error - indicating that cout is an undeclared identifier, then change the line...

   #include <iostream.h>

   to the following two lines...

   #include <iostream>

   using namespace std;

  Step 2 - Input and Output

When your program first starts, after displaying a welcome screen there should be an invitation for the user to press ANY key in order to continue.

1. Investigate the following functions too see which method you want to use to achieve this:-

   system("pause");    getch();    cin    cin.getline

   Note: You may get some strange behaviour from the system("pause") and getch() functions - pausing right at the start of your program, even if it is supposed to pause later on. If so, make sure you have included the following lines of code...

   #include <iostream>

   using namespace std

   If you use getch you will need to include the library file conio.h. If you use system("pause") you will need to include the library file stdlib.h.

2. Using one of these functions, insert the code into main so that your program waits for the user to press ANY key before continuing.

3. On depression of any key, using cout, display the first test question to the user. All the questions for the test are in the appendix of the assignment paper. Here is the first one:-

Question 1
123 – 39 =
1 64
2 44
3 74
4 84

4. The brief is for the question to be laid out towards the centre of the display screen. You will need to experiment with the escape characters \n, \t and endl to get the layout similar to mine.

5. Use cin to get the users answer.

6. Once you are happy with the layout of your first question, type in code to display a second question. Use cin to get the users answer again.

7. Add comments to your code.

  Step 3 - Using Variables and Constants

You may have noticed that you have no way of keeping a record of the users score at present. To fix this you will create some variables.

1. To practice creating variables of the appropriate type, create the variables listed below. Declare them just before the main function. You will be using them in later exercises. Make sure you add comments.

   score - integer for holding the users score

   fScore - float for working out the users score as a percentage

2. Pretend that the user gets 1 out of 2 questions correct. Using the variables you created, write a few lines of code to display the users score in the format:-

   Your total score is: Number of correct questions / 10
Your percentage is: Score calculated as percent %

  Step 4 - Creating Character Arrays

You have no way of keeping a record of the users answer at present. To fix this:-

1. Create a char array variable with say 255 elements in which to store the users answers and change your code appropriately. I.e.

   cin >> userAns;

   Check your code is working properly by echoing the users answer to the screen. I.e.

   cout << userAns;

   Remove this line when you are happy that everything works ok.

2. To practice creating arrays, create the following variables. Declare them just before the main function. You will be using them in later exercises. Make sure you add comments.

   correctAnswer[2] - character array to hold the correct answer number for a question

   ansRecord[NUMQ] - integer array to hold record of users answers, element value of 1 means answer is correct

  Step 5 - Using Functions

You may have noticed that your code is getting disorganized. To fix this we will start using functions to organize code.

1. Create a new C++ header file in which to declare your function prototypes. At the top of your .cpp source code file, type in the #include directive to include your header file.
2. Create the following function in your source code file and move your code for displaying the users score into this function.

   void displayScore (void)

   Call this function from an appropriate place in the main function.
   
   Don't forget to declare the function prototype.
   
   Compile, link and run your program to check that everything works.

3. Now create the following function and move your code for displaying the questions into this function.

   void displayQuestions(void)

   Call this function from an appropriate place in the main function. Don't forget to declare the function prototype. Compile, link and run your program to check that everything works.

  Step 6 - Validation

You we be creating more of your own functions to organize your code. You will also be using some pre-defined functions to manipulate strings and character arrays.

1. Create the following function.

int getAns(void)

Don't forget to declare the function prototype. We want this function to get the users answer. In step 4, you should have created the variables correctAnswer and userAns. Move the line

cin >> userAns;

from main into this function and call the getAns from main.

2. When the user types in an answer to a question, the entry must be in the form of the letters 1, 2, 3 or 4. These entries must be validated. An incorrect entry must cause an error message to appear on screen and a request for re-entry of the selection letter. To do all this, create the following function:-

int validateAnswer(void)

Don't forget to declare the function prototype.

In the function, write code to check only one character was input by the user using the pre-defined strlen function. The function should return the length of the string which you should store in a variable called numChars.

In the function, write code to check for an integer input between 0 and 5. You should use the pre-defined function atoi to convert the string stored in userAns to an integer value. The atoi function will let you know if it cannot convert the string to an integer by returning 0. Catch the value returned in a variable called numChars.

Using the return value of the atoi function, we need to write code to check its value is one of the numbers, 1, 2, 3, or 4. We shall do that bit in step 8.

Finally, the validateAnswer should return a 1 if the user input was valid and a 0 if it was invalid but we shall also do that bit in step 8.

You should call the validateAnswer function from inside the getAns function.

3. Now create the following function.

int compareAns(void)

Don't forget to declare the function prototype. We want this function to compare the users answer against the correct answer for a particular question. In step 4, you should have created the variables correctAnswer and userAns. Using those variables, write code in this function to compare the two variables. The function should return the number if the variables the hold the same answer and 0 if they don't.

Note: You can use the pre-defined strcmp function to compare two strings.

  Step 7 - Operators

You will now use the equality and increment operators in your code.

1. In the compareAns you should have the strcmp function comparing the users answer with the correct answer. Change the code as follows:-

   if (strcmp(userAns, correctAnswer) == 0)
  return 1;
else
  return 0;

   Notice the use of the equality operator. Compile, link and run your program to check that everything works.

2. In my main function I have a variable called questionCount which is incremented every time a question is asked of the user. I.e.

questionCount++;

Find an appropriate place in your code to put this line and don't forget to declare it as well.

  Step 8 - Conditional Statements

You will now include if...else and switch statements in your code.

1. We need to finish off the validateAnswer function that we started in step 6, so that the function returns a 1 if the user input was valid and a 0 if it was invalid.

   To do this first declare a integer variable called validate and initialize it to 0.

   then include an if...else statement as follows:-

   if (numChars == 1) validate = 1;
else validate = 0;

   You should also have already created some code that gets the integer value of the users answer back using the atoi function. Now you need to check for an integer input between 0 and 5. So include an if...else statement that sets validate to 0 or 1 depending if the input is between 0 and 5 or not.

   Now return the value of the validate variable from the validateAnswer function. Compile, link and run your program to check that everything works.

2. You should have created a function called displayQuestions in step 5. You will have probably written out a series of questions to be displayed to the user. But how do you control which question is displayed at any one time in your program? One way is to use the switch statement. First change your displayQuestions declaration as follows:-

   int displayQuestions(int qNumber)

   Don't forget to update the prototype.

   Inside this function you should use the switch function. To start you off I will give you a little bit of my code:-

   switch( qNumber )
{
case 1:
 strcpy (questionBuff, "\n\t\tQuestion 1:\n\t\t123 - 39 =");
 strcpy (opt1Buff , "64");
 strcpy (opt2Buff , "44");
 strcpy (opt3Buff , "74");
 strcpy (opt4Buff , "84");
 strcpy (correctAnswer,"4");
break;

   Finish off this switch function by including at least one more question and a default case.

   You should also declare the variables questionBuff etc. at the top of displayQuestions function. Here is one variable declaration, you do the rest:-

   char questionBuff[255];

   Change any cout statement you have, that display the questions and answers to the user, so that the appropriate variables are used instead. Here is one line as an example, you do the rest:-

   cout<< questionBuff << endl;

   Call the function from main, using a number to indicate which question you want displayed. I.e.

   displayQuestions (1);

   Compile, link and run your program to check that everything works.

  Step 9 - Loops

You will now include loop statements in your code.

1. When you check the users answer using validateAnswer, what should you do if the input is invalid? You should let them input again. To do that, wherever you are calling the validateAnswer function from in your code, insert an if statement as follows:-

   if (validateAnswer() != 1)
{
  cout << "Invalid input!\n" << "Enter 1 to 4 to specify the correct   answer." << endl;
}

   You need to put this inside a do...while loop, so that the user has to enter input until it is valid. Do that then compile, link and run your program to check that everything works.

2. I expect you call the displayQuestions function in main a number of times. I.e.

   displayQuestions(1);

   displayQuestions(2);

   Well what if you have lots of questions to display? You could keep on adding displayQuestions lines but it is simpler to use a loop. So, add a loop to you code so that you only have one displayQuestions line but all of your questions are displayed in turn.

   You will need to move your getAns and compareAns functions inside this loop too. You will also need to update the score variable inside the loop.

3. In the function main, you need to update the score variable every time the user chooses the correct answer. Now, every time you call the compareAns function, it returns a value of 1 if a question was answered correctly and 0 if it was answered incorrectly. So all we have to do to update score is write a line such as:-

   score = score + compareAns;

  Step 10 - Local and Global Variables

So far you have been creating variables without considering if they are local or global. Most of them will probably be global. Your task now is to try to eliminate as many global variables as you can and make them local.

1. You created a global score variable in an earlier exercise. Move the declaration of the variable into main. You also created a function called displayScore that needs to access to the score variable. Try compiling your code and you will see an error message displayed now because displayScore cannot access score. However, instead of changing score back to global, change the declaration of displayScore as follows:-

   void displayScore (void)

   to

   void displayScore (int ascore)

   and change all references to score inside the function to ascore. Don't forget to change the function prototype.

   When you call displayScore from main, you can just pass the score parameter. I.e.

   displayScore (score)

   Compile, link and run your program to check that everything works.

2. Now look through the rest of your code and change as many global variables as possible to local variables. I wouldn't expect more than a handful of global variables.

  Step 11 - More on Functions

Here is an example of a function that passes a character array variable by reference:-

1. I have the following function in my program, that displays any incorrectly answered questions to the user:-

   void showIncorrectAns (int score,int record[])
{
/* If score is less than the number of questions,
   display the questions incorrectly answered */
   
   if (score < NUMQ) // check if score is less than number of questions
   {
  cout << "The questions incorrectly answered were:" << endl <<endl;

     //loop through record of answers,
     //if element value is 0 question was incorrectly answered
     //if element value is 1 question was correctly answered
   
     for (int i = 0;i < NUMQ; i++)
  {
    if (record[i] == 0)
    {
      cout << "\t\t\t\t\tQuestion " << i+1 <<endl <<endl;
    }
  }

   }
else
  cout << "You answered all the questions correctly:" << endl;

   }

   Is the record[] parameter passed to the function by value or by reference?

   You can use this function in your own code if your wish. However, you will need to update the record[] array every time the user input the answer to a question somewhere in your code.

  Step 12 - Testing your Program

However far you have got with this practice assignment, it is time to test the program. We shall carry out black-box testing where the expected outputs are compared with actual outputs.

1. Create a testing table with at least 5 test cases. When creating each test case you should consider combinations of inputs where incorrect and correct answers are entered, invalid inputs are entered or the user wants to retake the test etc.