multiple choice test using C++

[Belinrahs]

Hello, for a final project in a class I am making a multiple choice test ABOUT C++, using C++. What I'm doing is using while loops and switch structures. The while loops are supposed to check whether the integer "error" is changed from it's default value (0), and the switch structures have 4 cases, A/B/C/D, which are of course the answers. If error is equal to 1 after the question is asked (the switch structure ends), the while loop will repeat the question. 2 problems thus far, 1.) the switch structure isn't recognizing my input as a valid case (it always defaults and sets error = 1), and 2.) when error is set to 1, the while loop isn't repeating the question! It is quitting the program.

There will be 20 questions, but I need to get the code right, then I can add the rest of the questions. Because the code is already in excess of 300 lines, I've attached the .CPP file. Thanks in advance for any assistance you can give me!

[GCDEF]

Just with a really quick glance your code could be simplified immensely using functions and loops.

Why not just create functions that ask the question and get the answer. Set up two arrays, one with the questions, one with the answers. Basically, you'd have

for(int i = 0; i < 20, i++)
{
    AskQuestion(i);
    GetAnswer(i);
}

That would be your main function pretty much.
Your GetAnswer function wouldn't need switch statements. It would just loop until the user entered the correct answer. Your whole program could be done in about 50 lines.

Even if you don't do that, and I strongly recommend you do, there's no need for switch statements. Just us an if.

if(answer != 'd' && answer != 'D')
    cout << "wrong";
else
   cout << "right";

Wrap that up in a while loop.

[GCDEF]

Why is letter choice a 2 char array?

letterChoice[2] is invalid memory. Valid indexes for an array of length 2 are 0 and 1.

[Belinrahs]

Unfortunately we didn't do functions in my class - it is an introductory course. The other problem is that the final project's minimal requirements are switch, if/then/else, loop and counter..and I can't use anything we haven't gone over in the class.

Personally I fully agree on using a simple if statement wrapped in a while loop. But it doesn't seem to fit the requirements I'm bound to -- I have to use switch in SOME way.

[Belinrahs]

Also, I set letterChoice to 2, because from what I've learned, if you need 1 letter stored, you need a place for 1.) the letter and 2.) the null terminator ( \0 ). Is this wrong?

[potatoCode]

Also, I set letterChoice to 2, because from what I've learned, if you need 1 letter stored, you need a place for 1.) the letter and 2.) the null terminator ( \0 ). Is this wrong?

For C-Style char arrays, yes that would be generally correct, but not all char* is necessarily null terminated.

Unfortunately we didn't do functions in my class - it is an introductory course. The other problem is that the final project's minimal requirements are switch, if/then/else, loop and counter..and I can't use anything we haven't gone over in the class.

So the requirement is that you use only while/if-else/switch and each has to be used at least once, correct?
One way would be to use while to loop as many as times there are questions, use switch to print questions, and if-else to determine the answer. It's still verbose but probably 2/3 less the lines allowed (300 lines)

[GCDEF]

For C-Style char arrays, yes that would be generally correct, but not all char* is necessarily null terminated.

So the requirement is that you use only while/if-else/switch and each has to be used at least once, correct?
One way would be to use while to loop as many as times there are questions, use switch to print questions, and if-else to determine the answer. It's still verbose but probably 2/3 less the lines allowed (300 lines)

That sounds like a better approach. At least you should consolidate your answer checking to

                   case 'A':
                   case 'a':
                  case 'C':
                   case 'c':
                   case 'D':
                   case 'd':
                         cout << "Sorry, that's the wrong answer. The correct answer is B!" << endl;
                        error = 0;
                        break;
                   case 'B':
                   case 'b':
                        cout << "Great! That's the right answer!" << endl;
                        correctAnswers++;
                        error = 0;
                        break;
                   default:
                        cout << "That isn't a valid answer. Please try the question again." << endl;
                        error = 1;
                        break;

but again, I think an if statement is more appropriate here.

[Belinrahs]

I redid a lot of the program using the tips you guys gave and I'm having another problem. Seems the loops are looping..repeatedly, extremely fast. Compile this for yourself and see the mess that happens.

Unless you guys have any tips I'm likely rewriting the whole thing using if loops, and perhaps, to fit the requirement, a case loop that prints different messages based on the score the user got. The thing's due on Monday, unfortunately..

Thanks for the tips - hoping I can get a few more pointers here to get me in the right direction.

[GCDEF]

Same problem I mentioned before. Don't make letterchoice an array.

The greatest allowable index for an array is 1 less than its size. Since you declared letterChoice as char[1], which doesn't really make sense to do, the ONLY allowable index for it is 0. letterChoice[1] references memory your app doesn't own. Just make letterChoice a char and stop trying to use it as an array.

I don't use the streams much so I'm not sure what cin.get does but cin >> letterChoice ought to be sufficient.

[Belinrahs]

Kudos GCDEF! I simply did char letterChoice, used cin >> letterChoice, and I also needed to set error to 1 before each while loop. (I could change that but it works, and that's what counts)

I'm indebted - I'll be able to turn in this final project and get a good score!

I'm sure I'll be back for help (besides just random posts and surfing the forums), but hopefully not too soon

[potatoCode]

That sounds like a better approach. At least you should consolidate your answer checking to

                   case 'A':
                   case 'a':
                  case 'C':
                   case 'c':
                   case 'D':
                   case 'd':
                         cout << "Sorry, that's the wrong answer. The correct answer is B!" << endl;
                        error = 0;
                        break;
                   case 'B':
                   case 'b':
                        cout << "Great! That's the right answer!" << endl;
                        correctAnswers++;
                        error = 0;
                        break;
                   default:
                        cout << "That isn't a valid answer. Please try the question again." << endl;
                        error = 1;
                        break;

but again, I think an if statement is more appropriate here.

That surely is one way.
I was thinking of using the char* as the "answer sheet" in a way such that

 // each letter represents the correct choice for the questions
    // answer for Q1 is 'b', Q2 is 'a', Q3 is 'd'
    const char* answerSheet = "bad";

would assign a single task to while/if-else/switch in

while( /* while there are questions */ )
    {
        switch(currentQuestion)
        {
            case 1:
                cout << "Question 1: What command prints something to the screen?" << endl;
                cout << "A: cin" << endl << "B: cout" << endl << "C: char" << endl << "D: print" << endl;
                break;
            case 2:
                cout << "Question 2: Which of the following is the default output device?" << endl;
                cout << "A: screen" << endl << "B: printer" << endl << "C: mouse" << endl << "D: keyboard" << endl;
                break;
        }
        cin >> letterChoice;

        // modify to make it case insensitive
        if(letterChoice == answerSheet[currentQuestion - 1])
        {
            cout << "Great! That's the right answer!" << endl;
            // ...
        }
        else
        {
            cout << "Sorry, that's the wrong answer. The correct answer is ";
            // print the correct answer
            // do whatever else is necessary
        }
         ++currentQuestion;
    }

[GCDEF]

I know what you meant. I thought your approach made more sense than his. I was just showing him how to simplify is switch statements if he chose to stick with what he had.