Assignment Programming
Lab 9
Practice Objectives of this Lab:
1. Modular Programming
2. Defining and Calling Functions
3. Function Prototypes
4. Sending Data into a Function
5. Passing Data by Value
6. The return Statement
7. Returning a Value from a Function
8. Returning a Boolean Value
9. Using Functions in a Menu-Driven Program
10. Local and Global Variables
11. Arrays as Function Arguments
12. Static Local Variables
13. Using Reference Variables as Parameters
Grading:
1. 9.1 10 points
9.2-9.7 15 points each
100 points totally
2. Your final complete solution report is due at 11:50 PM on Monday, 05/19/2014.
To begin
· Log on to your system and create a folder named Lab9 in your work space.
· Start the C++ IDE (Visual Studio) and create a project named Lab9.
LAB 9.1 – TRY IT: Working with Functions and Function Calls
Step 1: Add the tryIt6A.cpp program in your Lab6 folder to the project. Below is a partial listing of the source code.
| 1 // Lab 6 tryIt6A
12 /***** main *****/ 13 int main() 14 { int value = 2; 15 16 cout << “Hello from main.\n”; 17 printMessage(); 18 19 cout << “\nValue returned by tripleIt is ” 20 << tripleIt(value) << endl; 21 cout << “In main value now is ” 22 << value << endl << endl; 23 24 value = tripleIt(value); 25 cout << “In main value now is ” 26 << value << endl; 27 28 value = tripleIt(value); 29 cout << “In main value now is ” 30 << value << endl << endl; 31 32 cout << “Goodbye from main.\n”; 33 return 0; 34 } 35 36 /***** printMessage *****/ 37 void printMessage() 38 { 39 cout << “Hello from PrintMessage.\n”; 40 } 41 42 /***** tripleIt *****/ 43 int tripleIt(int someNum) 44 { 45 return someNum * someNum * someNum; 46 } |
Expected Output |
| |
Observed Output |
Step 2: Read the source code, paying special attention to the flow of control from main to the functions it calls and then back to main again. Notice what main passes to each function and what, if anything, the function return. Once you have done this, complete the “Expected Output” box in the table above, writing down what the program will display in the order it will be displayed.
Step 3: Now compile and run the tryIt6A.cpp program, and look at the output it creates. If the actual output matches what you wrote down, just place a checkmark in the “Observed Output” box. If it is not the same, write down the actual output.
LAB 9.2 – Using a void Function
Step 1: Remove tryIt6A.cpp from the project and add the fortunes.cpp program in your Lab6 folder to the project. Below is a copy of the source code.
1 // Lab 6 fortunes.cpp 2 // This fortune telling program will be modified to use a void function. 3 // PUT YOUR NAME HERE. 4 #include <iostream> 5 #include <cmath> 6 using namespace std; 7 8 // Function prototype 9 // WRITE A PROTOTYPE FOR THE tellFortune FUNCTION HERE. 10 11 /***** main *****/ 12 int main() 13 { 14 int numYears, 15 numChildren; 16 17 cout << “This program can tell your future. \n” 18 << “Enter two integers separated by a space: “; 19 20 cin >> numYears >> numChildren; 21 22 numYears = abs(numYears) % 5; // Convert to a positive integer 0 to 4 23 numChildren = abs(numChildren) % 6; // Convert to a positive integer 0 to 5 24 25 cout << “\nYou will be married in ” << numYears << ” years ” 26 << “and will have ” << numChildren << ” children.\n”; 27 28 return 0; 29 } 30 31 /***** tellFortune *****/ 32 // WRITE THE tellFortune FUNCTION HEADER HERE.
33 // WRITE THE BODY OF THE tellFortune FUNCTION HERE.
Step 2: Run the program to see how it works. What output do you get when you input the following values at the prompt? -99 14
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Step 3: Create a function that contains the fortune telling part of the code by doing the following:
· On line 9 write the prototype for a void function named tellFortune that has two integer parameters.
· On line 32 write the function header for the tellFortune function. Following that should be the body of the function. Move lines 22 – 26 of the program to the function body.
· Replace current lines 22 – 26 of main with a call to the tellFortune function that passes it two arguments, numYears and numChildren.
Step 4: Recompile and rerun the program. Enter -99 and 14 again. It should work the same as before.
Step 5: If your professor asks you to do so, print the revised source code and the output of executing it several times, using a variety of inputs.
LAB 9.3 – Modularizing a Program with void Functions
Step 1: Please see a copy of the completed areas2.cpp program and place it in your Lab6 folder. Name it areas3.cpp
// Lab 5 areas2-KEY.cpp
// This menu-driven program finds areas of squares,
// circles, and right triangles.
// It modifies the Lab 4 areas.cpp program to use a do-while loop.
// STUDENT NAME GOES HERE.
#include <iostream>
using namespace std;
int main()
{
const double PI = 3.14159;
double side, // Length of a side of a square
radius, // Radius of a circle
base, // Length of base of a right triangle
height, // Height of a right triangle
area; // Area of a square, circle, or right triangle.
int choice; // User’s menu choice
do
{
// Display the menu
cout << “\n\nProgram to calculate areas of different objects \n\n”;
cout << ” 1 — square \n”
<< ” 2 — circle \n”
<< ” 3 — right triangle \n”
<< ” 4 — quit \n\n”;
cin >> choice;
// Find and display the area of the user’s chosen object
if (choice == 1) // square
{ cout << “Length of the square’s side: “;
cin >> side;
area = side * side;
cout << “Area = ” << area << endl;
}
else if (choice == 2) // circle
{ cout << “Radius of the circle: “;
cin >> radius;
area = PI * radius * radius;
cout << “Area = ” << area << endl;
}
else if (choice == 3) // right triangle
{ cout << “Base of the triangle: “;
cin >> base;
cout << “Height of the triangle: “;
cin >> height;
area = .5 * base * height;
cout << “Area = ” << area << endl;
}
else if (choice != 4)
cout << “Choice must be 1, 2, 3, or 4.\n”;
} while (choice != 4);
return 0;
}
Step 2: Remove fortunes.cpp from the project and add the areas3.cpp program to the project.
Step 3: Modularize the program by adding the following 4 functions. None of them have any parameters.
· void displayMenu()
· void findSquareArea()
· void findCircleArea()
· void findTriangleArea()
To do that you will need to carry out the following steps:
· Write prototypes for the four functions and place them above main.
· Write function definitions (consisting of a function header and initially empty body) for the four functions and place them below main.
· Move the appropriate code out of main and into the body of each function.
· Move variable definitions in main for variables no longer in main to whatever functions now use those variables. They will be local variables in those functions. For example, findSquareArea will need to define the side variable and findCircleArea will need to define the radius variable. All of the functions that compute areas will now need to define a variable named area.
· Move the definition for the named constant PI out of main and place it above the main function.
· In main, replace each block of removed code with a function call to the function now containing that block of code.
Step 4: Compile the code, fixing any errors until it compiles without errors. Then test it. Make sure it runs correctly for all menu choices.
Step 5: If your professor asks you to do so, print the revised source code and the output of executing it , selecting each menu choice at least once.
LAB 9.4 – Using a Function that Returns a Value
Step 1: Remove areas3.cpp from the project and add the choice.cpp program in your Lab6 folder to the project. Below is a copy of the source code.
1 // Lab 6 choice.cpp 2 // This program illustrates how to use a value-returning 3 // function to get, validate, and return input data. 4 // PUT YOUR NAME HERE. 5 #include <iostream> 6 #include <cmath> 7 using namespace std; 8 9 // Function prototype 10 int getChoice(); 11 12 /***** main *****/ 13 int main() 14 { 15 int choice; 16 17 cout << “Enter an integer between 1 and 4: “; 18 19 // WRITE A LINE OF CODE TO CALL THE getChoice FUNCTION AND TO 20 // ASSIGN THE VALUE IT RETURNS TO THE choice VARIABLE. 21 22 cout << “You entered ” << choice << endl; 23 } 24 25 /***** getChoice *****/ 26 int getChoice() 27 { 28 int input; 29 30 // Get and validate the input 31 cin >> input; 32 while (input < 1 || input > 4) 33 { cout << “Invalid input. Enter an integer between 1 and 4: “; 34 cin >> input; 35 } 36 return input; 37 }
Step 2: Read through the code to see how it works. Notice that the getChoice function validates the input before returning it.
Step 3: Follow the directions given in the uppercase comments on lines 4 and 19-20. Then compile and run the program. When prompted for an input, use the data shown in the sample run below. You should get the same results.
Sample Run
Enter an integer between 1 and 4: 0
Invalid input. Enter an integer between 1 and 4: 9
Invalid input. Enter an integer between 1 and 4: 2
You entered 2
Step 4: Now make the getChoice function more versatile so it can validate that a choice is in any desired range, not just 1 – 4. Do this by carrying out the following steps:
· Add two integer parameters named min and max to the function header and modify the function prototype to agree with this.
· Revise the function so that it now validates that the input is between min and max. Remember to change the error prompt as well as the test condition of the while loop.
· Revise the line of code in main that calls the function so that it now passes two arguments to the function. Pass the values 1 and 4 to the function (though other values would work also).
Now recompile and rerun the program, again using the data from the sample run shown above. The program should produce the same results as it did before.
Step 5: If your professor asks you to do so, print the revised source code and the output of executing it with the sample run data.
Lab 9.5 – Modularizing a Program with Value-Returning Functions
For this lab exercise you will make additional improvements to the areas program you worked on in Lab 4, Lab 5, and earlier in this lab.
Step 1: In your Lab6 folder make a copy of your areas3.cpp file. Name it areas4.cpp
Step 2: Remove choice.cpp from the project and add the areas4.cpp program to the project.
Step 3: Copy the getChoice function you just wrote in the choice.cpp file for the Lab 6.4 exercise and paste it below the displayMenu function definition in the areas4.cpp file. Add a function prototype for the getChoice function at the top of the program where the other prototypes are located. Now, change the following line of code in main
cin >> choice;
to
choice = getChoice(1, 4);
This will ensure that choice is assigned a value between 1 and 4. Therefore the final else if can be removed from the if/else if statement that controls the branching. After doing this, test the program to make sure everything works so far, before going on to the next step.
Step 4: Now, make the findSquareArea, findCircleArea, and findTriangleArea functions into value-returning functions. They should each return a double value. Change their function headers and function prototypes to indicate this. Then, instead of having them print the area, have them return the area they have computed. Finally, change the call to each of these functions in main so that the value returned by the function call will be printed. For example, you will change
if (choice == 1)
findSquareArea();
to
if (choice == 1)
cout << “Area = ” << findSquareArea() << endl;
Step 5: Compile the code, fixing any errors until it compiles without errors. Then test it. Make sure it runs correctly for all menu choices.
Step 6: If your professor asks you to do so, print the revised source code and the output of executing it , selecting each menu choice at least once.
Lab 9.6 – Using Value and Reference Parameters
Step 1: Remove areas4.cpp from the project and add the swapNums.cpp program in your Lab6 folder to the project. Below is a copy of the source code.
1 // Lab 6 swapNums.cpp — Using Value and Reference Parameters 2 // This program uses a function to swap the values in two variables. 3 // PUT YOUR NAME HERE. 4 #include <iostream> 5 using namespace std; 6 7 // Function prototype 8 void swapNums(int, int); 9 10 /***** main *****/ 11 int main() 12 { 13 int num1 = 5, 14 num2 = 7; 15 16 // Print the two variable values 17 cout << “In main the two numbers are ” 18 << num1 << ” and ” << num2 << endl; 19 20 // Call a function to swap the values stored 21 // in the two variables 22 swapNums(num1, num2); 23 24 // Print the same two variable values again 25 cout << “Back in main again the two numbers are ” 26 << num1 << ” and ” << num2 << endl; 27 28 return 0; 29 } 30 31 /***** swapNums *****/ 32 void swapNums(int a, int b) 33 { // Parameter a receives num1 and parameter b receives num2 34 // Swap the values that came into parameters a and b 35 int temp = a; 36 a = b; 37 b = temp; 38 39 // Print the swapped values 40 cout << “In swapNums, after swapping, the two numbers are ” 41 << a << ” and ” << b << endl; 42 }
Step 2: Read the source code, paying special attention to the swapNums parameters. When the program is run do you think it will correctly swap the two numbers? Compile and run the program to find out.
Explain what happened. _________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
Step 3: Change the two swapNums parameters to be reference variables. Section 6.13 of your text shows how to do this. You will need to make the change on both the function header and the function prototype. Nothing will need to change in the function call. After making this change, recompile and rerun the program. If you have done this correctly, you should get the following output.
In main the two numbers are 5 and 7
In swapNums, after swapping, the two numbers are 7 and 5
Back in main again the two numbers are 7 and 5
Explain what happened this time. _________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
You do not need to hand in the source code or output from this lab exercise.
Lab 9.7 – Complete Program
Step 1: Remove swapNums.cpp from the project and add the kiloConverter.cpp program in your Lab6 folder to the project. This file contains just a program shell in which you will write the programming statements needed to complete the program described below. Here is a copy of the file.
1 // Lab 6 kiloConverter.cpp 2 // This menu-driven program lets the user convert 3 // pounds to kilograms and kilograms to pounds. 4 // PUT YOUR NAME HERE. 5 #include <iostream> 6 using namespace std; 7 8 // Function prototypes 9 // WRITE PROTOTYPES FOR THE displayMenu, getChoice, 10 // kilosToPounds and poundsToKilos FUNCTIONS HERE. 11 12 /***** main *****/ 13 int main() 14 { 15 // DECLARE ANY VARIABLES MAIN USES HERE. 16 17 // WRITE THE CODE HERE TO CARRY OUT THE STEPS 18 // REQUIRED BY THE PROGRAM SPECIFICATIONS. 19 20 return 0; 21 } 22 23 /***** displayMenu *****/ 24 // WRITE THE displayMenu FUNCTION HERE. 25 // THIS void FUNCTION DISPLAYS THE MENU CHOICES 26 // 1. Convert kilograms to pounds 27 // 2. Convert pounds to kilograms 28 // 3. Quit 29 30 /***** getChoice *****/ 31 // THIS IS THE SAME FUNCTION YOU WROTE EARLIER IN THIS SET 32 // OF LAB EXERCISES. JUST FIND IT AND PASTE IT HERE. 33 34 /***** kilosToPounds *****/ 35 // WRITE THE kilosToPounds FUNCTION HERE. 36 // IT RECEIVES A WEIGHT IN KILOS AND MUST CALCULATE 37 // AND RETURN THE EQUIVALENT NUMBER OF POUNDS. 38 39 /***** poundsToKilos *****/ 40 // WRITE THE poundsToKilos FUNCTION HERE. 41 // IT RECEIVES A WEIGHT IN POUNDS AND MUST CALCULATE 42 // AND RETURN THE EQUIVALENT NUMBER OF KILOS.
Step 2: Design and implement a modular, menu-driven program that converts kilograms to pounds and pounds to kilograms. 1 kilogram = 2.2 pounds. The program should display a menu, accept and validate a user menu choice, get the amount of weight to be converted, call the appropriate function to do the conversion, and then print the returned result. The code should continue iterating to allow additional conversions to be done until the user enters the menu choice to quit. When the program runs it should look somewhat like the sample run shown here.
Sample Run
1. Convert kilograms to pounds
2. Convert pounds to kilograms
3. Quit
1
Weight to be converted: 4
4 kilograms = 8.8 pounds.
1. Convert kilograms to pounds
2. Convert pounds to kilograms
3. Quit
2
Weight to be converted: 10
10 pounds = 4.54545 kilograms.
1. Convert kilograms to pounds
2. Convert pounds to kilograms
3. Quit
3
Step 3: Once your program is written and compiles with no errors, thoroughly test it.
Step 4: If your professor asks you to do so, print the completed source code and the output produced by executing it , selecting each menu choice at least once.
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