(Computer-Assisted Instruction: Reducing Student Fatigue) One problem in CAI environ- ments is student fatigue. This can be reduced by varying the computer’s responses to hold the stu- dent’s attention. Modify the program of Exercise 5.56 so that various comments are displayed for each answer as follows:

Question

Possible responses to a correct answer:
Very good!
Excellent!
Nice work!
Keep up the good work!
Possible responses to an incorrect answer:
No. Please try again.
Wrong. Try once more.
Don't give up!
No. Keep trying.
Use random-number generation to choose a number from 1 to 4 that will be used to select
one of the four appropriate responses to each correct or incorrect answer. Use a switch statement to
issue the responses.

Answer 1

```
// Help user practice multiplication.
#include
#include
#include
using namespace std;

int generateProblem(); // function prototype
void correctMessage(); // function prototype
void incorrectMessage(); // function prototype

int main()
{
int response = 0; // user response for product

srand( time( 0 ) ); // seed random number generator

// loop until sentinel value read from user
while ( response != -1 )
{
int answer = generateProblem(); // get product
cin >> response; // read user's guess

// loop until sentinel value or correct response
while ( response != -1 && response != answer )
{
incorrectMessage();
cin >> response;
} // end while

// correct response
if ( response == answer )
correctMessage();
} // end while

cout << "That's all for now. Bye." << endl;
} // end main
// generates new product and displays prompt
int generateProblem()
{
int x = rand() % 10; // generate 1-digit random number
int y = rand() % 10; // generate 1-digit random number

cout << "How much is " << x << " times " << y << " (-1 to End)\n? ";

return x * y; // return product
} // end function generateProblem

// correctMessage randomly chooses response to correct answer
void correctMessage()
{
// generate random number between 0 and 3
switch ( rand() % 4 )
{
case 0:
cout << "Very good!";
break;
case 1:
cout << "Excellent!";
break;
case 2:
cout << "Nice work!";
break;
case 3:
cout << "Keep up the good work!";
break;
} // end switch

cout << endl << endl;
} // end function correctMessage

// incorrectMessage randomly chooses response to incorrect answer
void incorrectMessage()
{
// generate random number between 0 and 3
switch ( rand() % 4 )
{
case 0:
cout << "No. Please try again.";
break;
case 1:
cout << "Wrong. Try once more.";
break;
case 2:
cout << "Don't give up!";
break;
case 3:
cout << "No. Keep trying.";
break;
} // end switch

cout << endl << "? ";
} // end function incorrectMessage
```