Person 1 (Apriyanti, Mirna) Translate to Indonesia & presentation … · Person 1 (Apriyanti,...

Person 1 (Apriyanti, Mirna)

Translate to Indonesia & presentation

Starting Out with C++, 3rd Edition

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presentation

Start Next Week Personal Number 1 & 2 & 3

Chapter 6 Functions


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6.1 Focus on Software Engineering: Breaking Up Your Programs

• Programs may be broken up into many manageable functions.


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6.2 Defining and Calling Functions

• A function call is a statement that causes a function to execute. A function definition contains the statements that make up the function.

• The line in the definition that reads


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• The line in the definition that reads void main(void) is called the function header.

Figure 6-1

Return Type

Name

Parameter List (This one is empty)

Body


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void main(void){

cout << “Hello World\n”;}

Calling a Function

• Function Headervoid displayMessage()

• Function Call


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• Function CalldisplayMessage();

Program 6-1#include <iostream.h>

//******************************************

// Definition of function displayMessage. *

// This function displays a greeting. *

//******************************************

void displayMessage()

{

cout << "Hello from the function displayMessage. \ n";


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}

void main(void)

{

cout << "Hello from main.\n";

displayMessage();

cout << "Back in function main again.\n";

}

Program Output

Hello from main.Hello from the function displayMessage.Back in function main again.


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Figure 6-2

void main(void)

void displayMessage(){

cout << “Hello from the function displayMessage.\n” ;}


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void main(void){

cout << “Hello from main.\n”;displayMessage();cout << “Back in function main again.\n”;

}

Program 6-2//The function displayMessage is repeatedly called from a loop

#include <iostream.h>

//******************************************

// Definition of function displayMessage. *

// This function displays a greeting. *

//******************************************

void displayMessage()

{



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}

void main(void)

{

cout << "Hello from main.\n";

for (int count = 0; count < 5; count++)

displayMessage(); // Call displayMessage


}

Program Output

Hello from main.Hello from the function displayMessage.Hello from the function displayMessage.Hello from the function displayMessage.


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Hello from the function displayMessage.Hello from the function displayMessage.Back in function main again.

Program 6-3

// This program has three functions: main, first, and second.


//*************************************

// Definition of function first. *

// This function displays a message. *

//*************************************


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void first(void)

{

cout << "I am now inside the function first.\n";

}

Program continues//*************************************

// Definition of function second. *


//*************************************

void second(void)

{

cout << "I am now inside the function second.\n";

}


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void main(void)

{

cout << "I am starting in function main.\n";

first(); // Call function first

second(); // Call function second


}

Program Output

I am starting in function main.I am now inside the function first.I am now inside the function second.Back in function main again.


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Back in function main again.

Figure 6-3void first(void){

cout << “I am now inside function first.\n”;}

void second(void){


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cout << “I am now inside function second.\n”;}

void main(void){

cout << “I am starting in function main.\n”;first();second();cout << “Back in function main again.\n”

}

Person 2 (Ricet, Riyana)


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Program 6-4// This program has three functions: main, deep, an d deeper


//**************************************

// Definition of function deeper. *



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//**************************************

void deeper(void)

{

cout << "I am now inside the function deeper.\n";

}

Program continues//**************************************// Definition of function deep. *// This function displays a message. *//**************************************void deep(){

cout << "I am now inside the function deep.\n";deeper(); // Call function deeper


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deeper(); // Call function deepercout << "Now I am back in deep.\n";

}void main(void){

cout << "I am starting in function main.\n";deep(); // Call function deepcout << "Back in function main again.\n";

}

Program Output

I am starting in function main.I am now inside the function deep.I am now inside the function deeper.Now I am back in deep.


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Now I am back in deep.Back in function main again.

Figure 6-4void deep(void){

cout << “I am now inside function deep.\n”;deeper();cout << “Now I am back in deep.\n”;

}

void deeper(void){


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cout << “I am now inside function deeper.\n”;}

void main(void){

cout << “I am starting in function main.\n”;deep();cout << “Back in function main again.\n”

}

Person 3 (Krisnawati, Adelia)


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6.3 Function Prototypes

• A function prototype eliminates the need to place a function definition before all calls to the function.

• Here is a prototype for the


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• Here is a prototype for the displayMessagefunction in Program 6-1

void displayMessage(void);

Program 6-5// This program has three functions: main, first, a nd second.


// Function Prototypes

void first(void);

void second(void);

void main(void)

{


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{

cout << "I am starting in function main.\n";

first(); // Call function first

second(); // Call function second

cout << “Back in function main again.\n";

}

Program Continues on next slide

Program 6-5 Continues// Definition of function first.

// This function displays a message.

void first(void)

{

cout << “I am now inside the function first.\n”;

}

// Definition of function second



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void second(void)

{

cout << “I am now inside the function second.\n”;

}

Program 6-5 Output

I am starting in function main.I am now inside the function first.I am now inside the function second.Back in function main again.


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Person 4 (Yafet, RianKalensun)


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6.4 Sending Information Into a Function

• When a function is called, the program may send values (arguments) into the function.

• Arguments are passed into parameters.


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void displayValue(int num){

cout << “The value is “ << num << endl;}

Program 6-6// This program demonstrates a function with a para meter.


// Function Prototype

void displayValue(int)

void main(void)

{


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cout << "I am passing 5 to displayValue.\n";

displayValue(5); //Call displayValue with argument 5

cout << "Now I am back in main.\n";

}

Program Continues to next slide

Program 6-6//*********************************************

// Definition of function displayValue. *

// It uses an integer parameter whose value is disp layed. *

//*********************************************

void displayValue(int num)

{

cout << “The value is “ << num << endl;

}


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Program Output

I ampassing 5 to displayValue.

The value is 5Now I am back in main.


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Figure 6-5

displayValue(5);



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void displayValue(int num){

cout << “The value is “ << num << endl;}

Program 6-7// This program demonstrates a function with a para meter.#include <iostream.h>

// Function Prototypevoid displayValue(int);

void main(void)

{

cout << "I am passing several values to displayValu e. \ n";


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cout << "I am passing several values to displayValu e. \ n";

displayValue(5); // Call displayValue with argumen t 5




cout << "Now I am back in main.\n";

}

Program continues on next slide

Program 6-7 Continued//*********************************************************

// Definition of function displayValue. *

// It uses an integer parameter whose value is displayed. *

//*********************************************************



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{

cout << "The value is " << num << endl;

}

Program Output

I am passing several values to displayValue.The value is 5The value is 10The value is 2


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The value is 2The value is 16Now I am back in main.

Program 6-8// This program demonstrates a function with three parameters.


// Function prototype

void showSum(int, int, int);

void main(void)


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void main(void)

{

int value1, value2, value3;

cout << "Enter three integers and I will display ";

cout << "their sum: ";

cin >> value1 >> value2 >> value3;

showSum(value1, value2, value3); // Call showSum with// 3 arguments

}

Program continues//************************************************************

// Definition of function showSum. *

// It uses three integer parameters. Their sum is displayed. *

//************************************************************

void showSum(int num1, int num2, int num3)

{

cout << (num1 + num2 + num3) << endl;


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cout << (num1 + num2 + num3) << endl;

}

Program Output with Example Input

Enter three integers and I will display their sum: 4 8 7 [Enter]

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Figure 6-6showSum(value1, value2, value3);

void showSum(int num1, int num2, int num3)


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void showSum(int num1, int num2, int num3){

cout << num1 + num2 + num3 << endl;}

Person 5 (Juli, Deasry)


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6.5 Changing the value of a Parameter

• When an argument is passed into a parameter, only a copy of the argument’s value is passed. Changes to the parameter


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value is passed. Changes to the parameter do not affect the original argument. This is called “passed by value.”

Program 6-9// This program demonstrates that changes to a func tion parameter

// have no effect on the original argument.


// Function Prototype

void changeThem(int, float);

void main(void)

{

int whole = 12;


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int whole = 12;

float real = 3.5;

cout << "In main the value of whole is " << whole < < endl;

cout << "and the value of real is " << real << endl ;

changeThem(whole, real); // Call changeThem with 2 a rguments

cout << "Now back in main again, the value of ";

cout << "whole is " << whole << endl;

cout << "and the value of real is " << real << endl ;

}

Program continues

//**************************************************************

// Definition of function changeThem. *

// It uses i, an int parameter, and f, a float. The values of *

// i and f are changed and then displayed. *

//**************************************************************

void changeThem(int i, float f)


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void changeThem(int i, float f)

{

i = 100;

f = 27.5;

cout << "In changeThem the value of i is changed to ";

cout << i << endl;

cout << "and the value of f is changed to " << f << endl;

}

Program Output

In main the value of whole is 12 and the value of real is 3.5In changeThem the value of i is changed to 100 and the value of f is changed to 27.5


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and the value of f is changed to 27.5Now back in main again, the value of whole is 12and the value of real is 3.5

Figure 6-7


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Person 6 (StevanyWuaten, Sinska)


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6.6 Focus on Software Engineering: Using Functions in a Menu-Driven Program

• Functions are ideal for use in menu-driven programs. When the user selects an item from a menu, the program can call the appropriate function.


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Program 6-10// This is a menu-driven program that makes a function call

// for each selection the user makes.


// Function Prototypes

void adult(int);


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void child(int);

void senior(int);

void main(void)

{

int choice, months;

Program continues

cout.setf(ios::fixed | ios::showpoint);

cout.precision(2);

do

{

cout << " \ n\ t \ tHealth Club Membership Menu \ n\ n";


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cout << " \ n\ t \ tHealth Club Membership Menu \ n\ n";

cout << "1. Standard adult Membership\n";

cout << "2. child Membership\n";

cout << "3. senior Citizen Membership\n";

cout << "4. Quit the Program\n\n";

cout << "Enter your choice: ";

cin >> choice;

Program continuesif (choice != 4)

{ cout << "For how many months? ";

cin >> months;

}

switch (choice)

{ case 1: adult(months);

break;


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break;

case 2: child(months);

break;

case 3: senior(months);

break;

case 4: cout << "Thanks for using this ";

cout << "program.\n";

break;

Program continuesdefault: cout << "The valid choices are 1-4. ";

cout << "Try again.\n";

}

} while (choice != 4);

}

//***********************************************************// Definition of function adult. Uses an integer pa rameter, mon. *

// mon holds the number of months the membership sh ould be *


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// calculated for. The cost of an adult membership for that many *

// months is displayed. *

//************************************************* *****************

void adult(int mon)

{

cout << "The total charges are $";

cout << (mon * 40.0) << endl;

}

Program continues//************************************************* *******************

// Definition of function child. Uses an integer pa rameter, mon. *


// calculated for. The cost of a child membership f or that many *

// months is displayed. *

//*************************************************************

void child(int mon)


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void child(int mon)

{


cout << (mon * 20.0) << endl;

}

Program continues

//************************************************* ******************

// Definition of function senior. Uses an integer p arameter, mon. *


// calculated for. The cost of a senior citizen mem bership for *

// that many months is displayed. *


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// that many months is displayed. *

//************************************************************

void senior(int mon)

{


cout << (mon * 30.0) << endl;

}

Program Output with Example InputHealth Club Membership Menu

1. Standard adult Membership

2. child Membership

3. senior Citizen Membership

4. Quit the Program

Enter your choice: 1


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For how many months 12

The total charges are $480.00

Health Club Membership Menu

1. Standard adult Membership

2. child Membership

3. senior Citizen Membership

4. Quit the Program

Enter your choice: 4

Thanks for using this program.

Person 7 (Helga, Destyani Maria)


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6.7 The return Statement

• The return statement causes a function to end immediately.


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Program 6-11// This program demonstrates a function with a return

statement.



void halfway(void);


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void main(void)

{

cout << "In main, calling halfway...\n";

halfway();

cout << "Now back in main.\n";

}

Program continues

//*********************************************************

// Definition of function halfway. *

// This function has a return statement that forces it to *

// terminate before the last statement is executed. *

//*********************************************************

void halfway(void)


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void halfway(void)

{

cout << "In halfway now.\n";

return;

cout <<"Will you ever see this message?\n";

}

Program Output

In main, calling halfway...In halfway now.Now back in main.


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Program 6-12// This program uses a function to perform division. If division

// by zero is detected, the function returns.


// Function prototype.

void divide(float, float);

void main(void)

{


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float num1, num2;

cout << "Enter two numbers and I will divide the first\n";

cout << "number by the second number: ";

cin >> num1 >> num2;

divide(num1, num2);

}

Program continues//************************************************* ***************

// Definition of function divide. *

// Uses two parameters: arg1 and arg2. The function divides arg1 *

// by arg2 and shows the result. If arg2 is zero, h owever, the *

// function returns. *

//************************************************* ***************

void divide(float arg1, float arg2)


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void divide(float arg1, float arg2)

{

if (arg2 == 0.0)

{

cout << "Sorry, I cannot divide by zero.\n";

return;

}

cout << "The quotient is " << (arg1 / arg2) << endl ;

}


Enter two numbers and I will divide the firstnumber by the second number: 12 0 [Enter]Sorry, I cannot divide by zero.


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Person 8 (Widya, Erni)


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6.8 Returning a value From a Function

• A function may send a value back to the part of the program that called the function.


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Figure 6-10


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Program 6-13

// This program uses a function that returns a valu e.


//Function prototype

int square(int);

void main(void)


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void main(void)

{

int value, result;

cout << "Enter a number and I will square it: ";

cin >> value;

result = square(value);

cout << value << " squared is " << result << endl;

}

Program continues

//************************************************* ***

// Definition of function square. *

// This function accepts an int argument and return s *

// the square of the argument as an int. *


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//************************************************* ***

int square(int number)

{

return number * number;

}


Enter a number and I will square it: 20 [Enter]20 squared is 400


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Figure 6-11

result = square(value);


20


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int square(int number){


}

Person 9 (Juliano, Kristian)


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6.9 Returning Boolean Values

• Function may return true or falsevalues.


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Program 6-15// This program uses a function that returns true o r false.



bool isEven(int);

void main(void)

{

int val;


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cout << "Enter an integer and I will tell you ";

cout << "if it is even or odd: ";

cin >> val;

if (isEven(val))

cout << val << " is even.\n";

else

cout << val << " is odd.\n";

}

Program continues

//************************************************* ********************

// Definition of function isEven. This function acc epts an *

// integer argument and tests it to be even or odd. The function *

// returns true if the argument is even or false if the argument is *

// odd. *

// The return value is bool. *

//************************************************* ********************

bool isEven(int number)

{


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{

bool status;

if (number % 2)

status = false; // The number is odd if there's a r emainder.

else

status = true; // Otherwise, the number is even.

return status;

}

Program Output

Enter an integer and I will tell you if it is even or odd: 5 [Enter]

5 is odd.


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Person 10 (Supardi, Yan Makarunggala , Stefanny Tangkuman)


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6.10 Local and Global Variables

• A local variable is declared inside a function, and is not accessible outside the function.


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function.

• A global variable is declared outside all functions and is accessible in its scope.

Program 6-16

// This program shows that variables declared in a function

// are hidden from other functions.


void func(void); // Function prototype


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void main(void)

{

int num = 1;

cout << "In main, num is " << num << endl;

func();

cout << "Back in main, num is still " << num << end l;

}

Program continues//*********************************************************

// Definition of function func. *

// It has a local variable, num, whose initial value, 20, *

// is displayed. *

//*********************************************************

void func(void)


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void func(void)

{

int num = 20;

cout << "In func, num is " << num << endl;

}

Program Output

In main, num is 1In func, num is 20Back in main, num is still 1


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Figure 6-8

Function main

num = 1 This numvariable is only visible in function main .


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Function func

num = 20 This numvariable is only visible in function func .

Program 6-17// This program shows that a global variable is visible

// to all the functions that appear in a program after

// the variable's declaration.



int num = 2; // Global variable


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void main(void)

{

cout << "In main, num is " << num << endl;

func();

cout << "Back in main, num is " << num << endl;

}

Program continues

//*****************************************************

// Definition of function func. *

// func changes the value of the global variable num *

//*****************************************************


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void func(void)

{


num = 50;

cout << "But, it is now changed to " << num << endl;

}

Program Output

In main, num is 2In func, num is 2But, it is now changed to 50Back in main, num is 50


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Back in main, num is 50

Program 6-18// This program shows that a global variable is visible

// to all the functions that appear in a program after

// the variable's declaration.




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void main(void)

{

cout << "In main, num is not visible!\n";

func();

cout << "Back in main, num still isn't visible!\n";

}

Program continues


//*****************************************************

// Definition of function func *

// func changes the value of the global variable num. *


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// func changes the value of the global variable num. *

//*****************************************************

void func(void)

{


num = 50;

cout << "But, it is now changed to " << num << endl;

}

Program Output

In main, num is not visible!In func, num is 2But, it is now changed to 50Back in main, num still isn't visible!


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Back in main, num still isn't visible!

Global Variables are Initialized to Zero by Default

• Unless you explicitly initialize numeric global variables, they are automatically initialized to zero.


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initialized to zero.

• Global character variables are initialized to NULL, or ASCII code 0.

Program 6-19// This program has an uninitialized global variable.


int globalNum; // Global variable. Automatically set to zero.

void main(void)

{


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{

cout << "globalNum is " << globalNum << endl;

}

Program Output

globalNum is 0


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Local and Global Variables with the Same Name

• If a function has a local variable with the same name as a global variable, only the local variable can be seen by the function.


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local variable can be seen by the function.

Program 6-20// This program shows that when a local variable ha s the

// same name as a global variable, the function onl y sees

// the local variable.


// Function prototypes

void texas();


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void arkansas();

int cows = 10;

void main(void){

cout << "There are " << cows << " cows in main.\n";texas();arkansas();cout << "Back in main, there are " << cows << " cow s.\n";

}

Program continues

//******************************************

// Definition of function texas. *

// The local variable cows is set to 100. *

//******************************************

void texas(void)

{

int cows = 100;


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cout << "There are " << cows << " cows in texas.\n" ;

}

Program continues

//******************************************

// Definition of function arkansas. *

// The local variable cows is set to 50. *

//******************************************


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void arkansas(void)

{

int cows = 50;

cout << "There are " << cows << " cows in arkansas.\n";

}

Program Output

There are 10 cows in main.There are 100 cows in texas.There are 50 cows in arkansas.Back in main, there are 10 cows.


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Back in main, there are 10 cows.

Program 6-21// This program has local and global variables. In the function

// ringUpSale, there is a local variable named tax. There is

// also a global variable with the same name.


void ringUpSale(void); // Function prototype


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// Global Variables

const float taxRate = 0.06;

float tax, sale, total;

void main(void)

{

char again;

Program continues

cout.precision(2);

cout.setf(ios::fixed | ios::showpoint);

do

{

ringUpSale();

cout << "Is there another item to be purchased? ";

cin >> again;

} while (again == 'y' || again == 'Y');


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tax = sale * taxRate;

total = sale + tax;

cout << "The tax for this sale is " << tax << endl;

cout << "The total is " << total << endl;

}

Program continues//************************************************* *****************

// Definition of function ringUpSale. *

// This function asks for the quantity and unit pri ce of an item. *

// It then calculates and displays the sales tax an d subtotal *

// for those items. *

//************************************************* *****************

void ringUpSale(void){


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{int qty;float unitPrice, tax, thisSale, subTotal;

cout << "Quantity: ";cin >> qty;cout << "Unit price: ";cin >> unitPrice;thisSale = qty * unitPrice; // Get the total unit p rice

Program continues

sale += thisSale; // Update global variable sale

tax = thisSale * taxRate; // Get sales tax for these items

subTotal = thisSale + tax; // Get subtotal for these items

cout << "Price for these items: " << thisSale << endl;


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cout << "Price for these items: " << thisSale << endl;

cout << "tax for these items: " << tax << endl;

cout<< "subTotal for these items: " << subTotal << endl;

}

Program Output with Example InputQuantity: 2 [Enter]Unit Price: 20.00 [Enter]Price for these items: 40.00tax for these items: 2.40subTotal for these items: 42.40Is there another item to be purchased? y [Enter]Quantity: 3 [Enter]


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Unit Price: 12.00 [Enter]Price for these items: 36.00tax for these items: 2.16subTotal for these items: 38.16Is there another item to be purchased? n [Enter]The tax for this sale is 4.56The total is 80.56

Be Careful With Global Variables

• It is tempting to make all your variables global. But don’t do it!

• Using global variables can cause problems.


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• Using global variables can cause problems.– It is harder to debug a program that uses global

variables

Person 11 (Niksen, Hermawan)


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6.11 Static Local Variables

• If a function is called more than once in a program, the values stored in the function’s local variables do not persist between


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local variables do not persist between function calls.

• To get a variable to keep it’s value even after the function ends, you must create static variables

Program 6-22// This program shows that local variables do not r etain

// their values between function calls.



void showLocal(void);


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void showLocal(void);

void main(void)

{

showLocal();

showLocal();

}

Program continues

//***********************************************************

// Definition of function showLocal. *

// The initial value of localNum, which is 5, is displayed. *

// The value of localNum is then changed to 99 before the *

// function returns. *

//***********************************************************


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void showLocal(void)

{

int localNum = 5; // Local variable

cout << "localNum is " << localNum << endl;

localNum = 99;

}

Program Output

localNum is 5localNum is 5


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Program 6-23//This program uses a static local variable.#include <iostream.h>void showStatic(void); // Function prototype

void main(void){

for (int count = 0; count < 5; count++)showStatic();

}

//************************************************* ************// Definition of function showStatic. *


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// Definition of function showStatic. *// statNum is a static local variable. Its value is displayed *// and then incremented just before the function re turns. *//************************************************* ************

void showStatic(void){

static int statNum;

cout << "statNum is " << statNum << endl;statNum++;

}

Program Output

statNum is 0statNum is 1statNum is 2statNum is 3


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statNum is 3statNum is 4

Program 6-24// This program shows that a static local variable is only

// initialized once.


void showStatic(void); // Function prototype

void main(void)


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void main(void)

{

for (int count = 0; count < 5; count++)

showStatic();

}

Program continues

//***********************************************************

// Definition of function showStatic. *

// statNum is a static local variable. Its value is displayed

// and then incremented just before the function returns. *

//***********************************************************


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void showStatic()

{

static int statNum = 5;

cout << "statNum is " << statNum << endl;

statNum++;

}

Program Output

statNum is 5statNum is 6statNum is 7statNum is 8


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statNum is 8statNum is 9

Person 12 (Korinus, Eka P. Paputungan)


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6.12 Default Arguments

• Default arguments are passed to parameters automatically if no argument is provided in the function call.


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the function call.

• A function’s default arguments should be assigned in the earliest occurrence of the function name. This will usually mean the function prototype.

Program 6-25// This program demonstrates default function argum ents.


// Function prototype with default arguments

void displayStars(int = 10, int = 1);

void main(void)

{


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{

displayStars();

cout << endl;

displayStars(5);

cout << endl;

displayStars(7, 3);

}

Program continues

//************************************************* *************

// Definition of function displayStars. *

// The default argument for cols is 10 and for rows is 1. *

// This function displays a rectangle made of aster isks. *

//************************************************* *************

void displayStars(int cols, int rows)

{


113

{

// Nested loop. The outer loop controls the rows

// and the inner loop controls the columns.

for (int down = 0; down < rows; down++)

{

for (int across = 0; across < cols; across++)

cout << "*";

cout << endl;

}

}

Program Output

**********

*****


114

*******

*******

*******

Default Argument Summary

• The value of a default argument must be a constant (either a literal value of a named constant).

• When an argument is left out of a function call (because it has a default value), all the arguments that come after it must be left out too.


115

must be left out too.• When a function has a mixture of parameters both with and

without default arguments, the parameters with default arguments must be declared last.

Person 13 (Yuyun, Ukasiah)


116

6.13 Using Reference Variables as Parameters

• When used as parameters, reference variables allow a function to access the parameter’s original argument, changes to


117

parameter’s original argument, changes to the parameter are also made to the argument.

Example:

void doubleNum(int &refVar)

{

refVar *= 2;

}


118

}

// The variable refVar is called

// “a reference to an int”

Program 6-26// This program uses a reference variable as a function

// parameter.


// Function prototype. The parameter is a reference variable.

void doubleNum(int &);

void main(void)


119

{

int value = 4;

cout << "In main, value is " << value << endl;

cout << "Now calling doubleNum..." << endl;

doubleNum(value);

cout << "Now back in main. value is " << value << endl;

}

Program continues

//************************************************************

// Definition of doubleNum. *

// The parameter refVar is a reference variable. The value *

// in refVar is doubled. *

//************************************************************


120

//************************************************************

void doubleNum (int &refVar)

{

refVar *= 2;

}

Program Output

In main, value is 4Now calling doubleNum...Now back in main. value is 8


121

Program 6-27// This program uses reference variables as function

// parameters.


// Function prototypes. Both functions use reference variables

// as parameters

void doubleNum(int &);

void getNum(int &);


122

void main(void)

{

int value;

getNum(value);

doubleNum(value);

cout << "That value doubled is " << value << endl;

}

Program continues

//*************************************************************

// Definition of getNum. *

// The parameter userNum is a reference variable. The user is *

// asked to enter a number, which is stored in userNum. *

//*************************************************************

void getNum(int &userNum)


123

void getNum(int &userNum)

{

cout << "Enter a number: ";

cin >> userNum;

}

Program continues

//************************************************************

// Definition of doubleNum. *

// The parameter refVar is a reference variable. The value *

// in refVar is doubled. *

//************************************************************


124

//************************************************************

void doubleNum (int &refVar)

{

refVar *= 2;

}


Enter a number: 12 [Enter]That value doubled is 24


125

Reference Argument Warning

• Don’t get carried away with using reference variables as function parameters. Any time you allow a function to alter a variable


126

you allow a function to alter a variable that’s outside the function, you are creating potential debugging problems. Reference variables should only be used as parameters when the situation demands them.

Person 14 (Serly, Denny)


127

6.14 Overloaded Functions

• Two or more functions may have the same name as long as their parameter lists are different.


128

different.

Program 6-28#include <iostream.h>

// Function prototypes

int square(int);

float square(float);

void main(void)

{

int userInt;


129

int userInt;

float userFloat;

cout.precision(2);

cout << "Enter an integer and a floating-point valu e: ";

cin >> userInt >> userFloat;

cout << "Here are their squares: ";

cout << square(userInt) << " and " << square(userFl oat);

}

Program continues

// Definition of overloaded function square.

// This function uses an int parameter, number. It returns the

// square of number as an int.


{


}


130

}

// Definition of overloaded function square.

// This function uses a float parameter, number. It returns the

// square of number as a float.

float square(float number)

{


}


Enter an integer and floating-point value: 12 4.2 [Enter]

Here are their squares: 144 and 17.64


131

Program 6-29// This program demonstrates overloaded functions t o calculate// the gross weekly pay of hourly-paid or salaried employees.#include <iostream.h>

// Function prototypesvoid getChoice(char &);float calcWeeklyPay(int, float);float calcWeeklyPay(float);

void main(void){


132

{char selection;int worked;float rate, yearly;

cout.precision(2);cout.setf(ios::fixed | ios::showpoint);cout << “Do you want to calculate the weekly pay of \n";cout << “(H) an hourly-paid employee, or \n”;cout << “(S) a salaried employee?\n”;

Program continuesgetChoice(selection);

switch (selection)

{

case ‘H’ :

case ‘h’ : cout << “How many hours were worked? “;

cin >> worked;

cout << “What is the hour pay rate? “;

cin >> rate;

cout << “The gross weekly pay is “;


133


cout << calcWeeklyPay(worked, rate);

break;

case ‘S’ :

case ‘s’ : cout << “What is the annual salary? “;

cin >> yearly;


cout << calcWeeklyPay(yearly);

break;

}

}

Program continues//***********************************************************

// Definition of function getChoice. *

// The parameter letter is a reference to a char. *

// This function asks the user for an H or an S and returns *

// the validated input. *

//***********************************************************

void getChoice(char &letter){


134

{do{

cout << “Enter your choice (H or S): “;cin >> letter;

} while (letter != ‘H’ && letter != ‘h’ &&letter != ‘S’ && letter != ‘s’);

}


// Definition of overloaded function calcWeeklyPay. *

// This function calculates the gross weekly pay of *

// an hourly-paid employee. The parameter hours hold the *

// hourly pay rate. The function returns the weekly salary. *

//***********************************************************

void calcWeekly(int hours, float payRate)


135

void calcWeekly(int hours, float payRate)

{

return hours * payRate;

}


// Definition of overloaded function calcWeeklyPay. *

// This function calculates the gross weekly pay of *

// a salaried employee. The parameter holds the employee’s *

// annual salary. The function returns the weekly salary. *

//***********************************************************

void calcWeekly(float annSalary)


136

void calcWeekly(float annSalary)

{

return annSalary / 52.0;

}

Program Output with Example InputDo you want to calculate the weekly pay of

(H) an houly-paid employee, or

(S) a salaried employee? H[Enter]

How many hours were worked? 40[Enter]

What is the hour pay rate? 18.50[Enter]

The gross weekly pay is 740.00


137

Program Output with Other Example InputDo you want to calculate the weekly pay of

(H) an houly-paid employee, or

(S) a salaried employee? S[Enter]

What is the annual salary? 48000.00[Enter]

The gross weekly pay is 923.08

Person 15 (Relvando, Gladis Ansiga)


138

6.15 The exit() Function

• The exit() function causes a program to terminate, regardless of which function or control mechanism is executing.


139

control mechanism is executing.

Program 6-30// This program shows how the exit function causes a program

// to stop executing.


#include <stdlib.h> // For exit

void function(void); // Function prototype


140

void function(void); // Function prototype

void main(void)

{

function();

}

Program continues

//***********************************************************

// This function simply demonstrates that exit can be used *

// to terminate a program from a function other than main. *

//***********************************************************


141

void function(void)

{

cout << "This program terminates with the exit function.\n";

cout << "Bye!\n";

exit(0);

cout << "This message will never be displayed\n";

cout << "because the program has already terminated.\n";

}

Program Output

This program terminates with the exit function.Bye!


142

Program 6-31// This program demonstrates the exit function.


#include <stdlib.h> // For exit

void main(void)

{

char response;


143

cout << "This program terminates with the exit func tion.\n";

cout << "Enter S to terminate with the EXIT_SUCCESS code\n";

cout << "or f to terminate with the EXIT_FAILURE co de: ";

cin >> response;

Program continues

if (response == 'S')

{

cout << "Exiting with EXIT_SUCCESS.\n";

exit(EXIT_SUCCESS);

}

else

{


144

{

cout << "Exiting with EXIT_FAILURE.\n";

exit(EXIT_FAILURE);

}

}

Program Output with Example InputThis program terminates with the exit function.Enter S to terminate with the EXIT_SUCCESS codeor f to terminate with the EXIT_FAILURE code: s [Enter]Exiting with EXIT_SUCCESS.

Program Output With Other Example Input


145

Program Output With Other Example InputThis program terminates with the exit function.Enter S to terminate with the EXIT_SUCCESS codeor f to terminate with the EXIT_FAILURE code: f [Enter]Exiting with EXIT_FAILURE.

Person 16 (Johra, Andika)


146

6.16 Stubs and Drivers

• Stubs and drivers are very helpful tools for testing and debugging programs that use functions.


147

functions.

• A stub is a dummy function that is called instead of the actual function it represents.

• A driver is a program that tests a function by simply calling it.

// Stub for the adult function.

void adult(int months)

{

cout << "The function adult was called with " << mo nths;

cout << " as its argument.\n";

}

// Stub for the child function.

void child(int months)

{

cout << "The function child was called with " << mo nths;

cout << " as its argument. \ n";


148

cout << " as its argument. \ n";

}

// Stub for the senior function.

void senior(int months)

{

cout << "The function senior was called with " << m onths;

cout << " as its argument.\n";

}

Person 17 (Kevin, Jonathan Tompodung, Abdulharis)


149

Functions and subprograms

• The Top-down design appeoach is based on dividing the main problem into smaller tasks which may be divided into simpler tasks, then implementing each simple task by a subprogram or a function

• A C++ function or a subprogram is simply a chunk of C++


150

• A C++ function or a subprogram is simply a chunk of C++ code that has– A descriptive function name, e.g.

•• computeTaxescomputeTaxes to compute the taxes for an employee •• isPrimeisPrime to check whether or not a number is a prime number

– A returning value• The computeTaxesomputeTaxes function may return with a double number

representing the amount of taxes• The isPrimeisPrime function may return with a Boolean value (true or false)

C++ Standard Functions

• C++ language is shipped with a lot of functions which are known as standard functions

• These standard functions are groups in different libraries which can be included in the C++ program, e.g.


151

libraries which can be included in the C++ program, e.g.– Math functions are declared in <math.h> library– Character-manipulation functions are declared in

<ctype.h> library– C++ is shipped with more than 100 standard libraries,

some of them are very popular such as <iostream.h> and <stdlib.h>, others are very specific to certain hardware platform, e.g. <limits.h> and <largeInt.h>

Example of Using Standard C++ Math Functions

#include <iostream.h>#include <math.h>void main(){


152

// Getting a double valuedouble x;cout << "Please enter a real number: ";cin >> x;// Compute the ceiling and the floor of the real numbercout << "The ceil(" << x << ") = " << ceil(x) << endl;cout << "The floor(" << x << ") = " << floor(x) << endl;

}

Example of Using Standard C++ Character Functions

#include <iostream.h> // input/output handling#include <ctype.h> // character type functionsvoid main(){

char ch;cout << "Enter a character: ";

Explicit casting


153

cin >> ch; cout << "The toupper(" << ch << ") = " << (char) toupper(ch) << endl;cout << "The tolower(" << ch << ") = " << (char) tolower(ch) << endl;if (isdigit(ch))

cout << "'" << ch <<"' is a digit!\n";else

cout << "'" << ch <<"' is NOT a digit!\n";}

User-Defined C++ Functions

• Although C++ is shipped with a lot of standard functions, these functions are not enough for all users, therefore, C++ provides its users with a way to define their own functions (or user-defined


154

to define their own functions (or user-defined function)

• For example, the <math.h> library does not include a standard function that allows users to round a real number to the ith digits, therefore, we must declare and implement this function ourselves

How to define a C++ Function?

• Generally speaking, we define a C++ function in two steps (preferably but not mandatory)


155

mandatory)– Step #1 – declare the function signaturefunction signature in

either a header file (.h file) or before the main function of the program

– Step #2 – Implement the function in either an implementation file (.cpp) or after the main function

What is The Syntactic Structure of a C++ Function?

• A C++ function consists of two parts– The function header, and

– The function body


156

– The function body

• The function header has the following syntax

<return value> <name> (<parameter <return value> <name> (<parameter list>)list>)

• The function body is simply a C++ code enclosed between { }

Example of User-definedC++ Function

double computeTax(double income)


157

double computeTax(double income){

if (income < 5000.0) return 0.0;double taxes = 0.07 * (income-5000.0);return taxes;

}



Function header


158



}



Function header

Function body


159



}

Function Signature

• The function signature is actually similar to the function header except in two aspects:– The parameters’ names may not be specified in

the function signature


160

the function signature– The function signature must be ended by a

semicolon

• Example

double computeTaxes(double) ;

Unnamed Parameter

Semicolon;

Why Do We Need Function Signature?

• For Information Hiding– If you want to create your own library and share it with

your customers without letting them know the implementation details, you should declare all the function signatures in a header (.h) file and distribute


161

function signatures in a header (.h) file and distribute the binary code of the implementation file

• For Function Abstraction– By only sharing the function signatures, we have the

liberty to change the implementation details from time to time to

• Improve function performance• make the customers focus on the purpose of the function, not

its implementation

Example#include <iostream>#include <string>using namespace std;

// Function Signaturedouble getIncome(string); double computeTaxes(double);void printTaxes(double);

double computeTaxes(double income){

if (income<5000) return 0.0;return 0.07*(income-5000.0);

}

double getIncome(string prompt){

cout << prompt;


162

void main(){

// Get the income;double income = getIncome("Please enter the employee income: ");

// Compute Taxesdouble taxes = computeTaxes(income);

// Print employee taxesprintTaxes(taxes);

}

double income;cin >> income;

return income;}

void printTaxes(double taxes){

cout << "The taxes is $" << taxes << endl;}

Person 18 (Andrew, DesyKaseger)


163

Building Your Libraries

• It is a good practice to build libraries to be used by you and your customers

• In order to build C++ libraries, you should be familiar with


164

• In order to build C++ libraries, you should be familiar with– How to create header files to store function

signatures– How to create implementation files to store

function implementations– How to include the header file to your program

to use your user-defined functions

C++ Header Files

• The C++ header files must have .h extension and should have the following structure– #ifndef compiler directive


165

– #ifndef compiler directive– #define compiler directive– May include some other header files– All functions signatures with some comments

about their purposes, their inputs, and outputs– #endif compiler directive

TaxesRules Header file

#ifndef _TAXES_RULES_#define _TAXES_RULES_

#include <iostream>#include <string>using namespace std;

double computeTaxes(double);// purpose -- to compute the taxes for a

given income// input -- a double value representing

the income// output -- a double value representing


166

using namespace std;

double getIncome(string); // purpose -- to get the employee

income// input -- a string prompt to be

displayed to the user// output -- a double value representing

the income

// output -- a double value representing the taxes

void printTaxes(double);// purpose -- to display taxes to the user// input -- a double value representing

the taxes// output -- None

#endif

TaxesRules Implementation File

#include "TaxesRules.h"

double computeTaxes(double income){

if (income<5000) return 0.0;return 0.07*(income-5000.0);

void printTaxes(double taxes){

cout << "The taxes is $" << taxes


167

return 0.07*(income-5000.0);}

double getIncome(string prompt){

cout << prompt;double income;cin >> income;return income;

}

cout << "The taxes is $" << taxes << endl;

}

Main Program File

#include "TaxesRules.h"void main(){

// Get the income;


168

double income = getIncome("Please enter the employee income: ");

// Compute Taxesdouble taxes = computeTaxes(income);

// Print employee taxesprintTaxes(taxes);

}

Inline Functions

• Sometimes, we use the keyword inline inline to define user-defined functions – Inline functions are very small functions, generally, one

or two lines of code


169

or two lines of code– Inline functions are very fast functions compared to the

functions declared without the inline keyword

• Exampleinlineinline double degrees( double radian)

{return radian * 180.0 / 3.1415;

}

Example #1• Write a function to test if a number is an odd

number

inline bool odd (int x)


170

inline bool odd (int x)

{

return (x % 2 == 1);

}

Example #2

• Write a function to compute the distance between two points (x1, y1) and (x2, y2)


171

Inline double distance (double x1, double y1,

double x2, double y2)

{

return sqrt(pow(x1-x2,2)+pow(y1-y2,2));

}

Example #3

• Write a function to compute n!

int factorial( int n)


172

int factorial( int n){

int product=1;for (int i=1; i<=n; i++) product *= i;return product;

}

Example #4Function Overloading

• Write functions to return with the maximum number of two numbers

inline int max( int x, int y){

An overloaded function is a

function that is defined more


173

{if (x>y) return x; else return y;

}

inline double max( double x, double y){

if (x>y) return x; else return y;}

defined more than once with different data

types or different

number of parameters

Person 19 (Arley, Arthur Toliu)


174

Sharing Data Among User-Defined Functions

• There are two ways to share data among different functions– Using global variables (very bad practice!)


175

– Passing data through function parameters• Value parameters

• Reference parameters

• Constant reference parameters

C++ Variables

• A variable is a place in memory that has– A name or identifier (e.g. income, taxes, etc.)– A data type (e.g. int, double, char, etc.)– A size (number of bytes)


176

– A size (number of bytes)– A scope (the part of the program code that can use it)

• Global variables – all functions can see it and using it• Local variables – only the function that declare local variables

see and use these variables

– A life time (the duration of its existence)• Global variables can live as long as the program is executed• Local variables are lived only when the functions that define

these variables are executed

I. Using Global Variables

#include <iostream.h>int x = 0;void f1() { x++; }void f2() { x+=4; f1(); }


177

void f2() { x+=4; f1(); }void main(){

f2();cout << x << endl;

}



x 0


178



}



x 0


179



}

void main()void main(){ {

f2();f2();cout << x << cout << x <<

endl ;endl ;}}

1



x 04


180



}


f2();f2();cout << x << cout << x <<

endl ;endl ;}}

1

void f2()void f2(){ {

x += 4;x += 4;f1();f1();

}}

2

45



x


x++;x++;}}

4


181



}


f2();f2();cout << x << cout << x <<

endl ;endl ;}}

1


x += 4;x += 4;f1();f1();

}}

3

}}

45



x


x++;x++;}}

5


182



}


f2();f2();cout << x << cout << x <<

endl;endl;}}

1


x += 4;x += 4;f1();f1();

}}

3

}}

45



x


183



}


f2();f2();cout << x << cout << x <<

endl;endl;}}

1


x += 4;x += 4;f1();f1();

}}6

45



x


184



}void main()void main(){ {

f2();f2();cout << x << cout << x <<

endl;endl;}}

7

45



x


185



}void main()void main(){ {

f2();f2();cout << x << cout << x <<

endl;endl;}}

8




186



}

What Happens When We Use Inline Keyword?


int x = 0;

InlineInline void f1() { x++; }

InlineInline void f2() { x+=4; f1();}


187


void main()

{

f2();

cout << x << endl;

}



int x = 0;



0x

The inline keyword instructs the

compiler to replace


188


void main()

{

f2();

cout << x << endl;

}


x+=4;x+=4;x++;x++;cout << x << endl;cout << x << endl;

}}

1

compiler to replace the function call with the function

body!



int x = 0;



4x


189


void main()

{

f2();

cout << x << endl;

}



}}

2



int x = 0;



5x


190


void main()

{

f2();

cout << x << endl;

}



}}

3



int x = 0;



5x


191


void main()

{

f2();

cout << x << endl;

}



}}

4



int x = 0;




192


void main()

{

f2();

cout << x << endl;

}

Person 20 (Masita Adam, Jonathan Tasyam)


193

What is Bad About UsingGlobal Vairables?

• Not safe!– If two or more programmers are working together in a

program, one of them may change the value stored in the global variable without telling the others who may


194

the global variable without telling the others who may depend in their calculation on the old stored value!

• Against The Principle of Information Hiding!– Exposing the global variables to all functions is against

the principle of information hiding since this gives all functions the freedom to change the values stored in the global variables at any time (unsafe!)

Local Variables

• Local variables are declared inside the function body and exist as long as the function is running and destroyed when the function exit

• You have to initialize the local variable before


195

• You have to initialize the local variable before using it

• If a function defines a local variable and there was a global variable with the same name, the function uses its local variable instead of using the global variable

Example of Defining and Using Global and Local Variables

#include <iostream.h>int x; // Global variable// Global variableVoid fun(); // function signature// function signature

void main(){


196

x = 4;fun();cout << x << endl;

}

void fun(){

int x = 10; // Local variable// Local variablecout << x << endl;

}



void main(){

x 0

Global variables are automatically initialized to

0


197


}

void fun(){


}



void main(){

x 0


198


}

void fun(){


}


x = 4;x = 4;fun();fun();cout << x << cout << x <<

endl;endl;

1



void main(){

x 4

void fun()void fun()

x ????


199


}

void fun(){


}



endl;endl;

2

{ { int x = 10;int x = 10;cout << x << cout << x <<

endl;endl;}}

x ????

3



void main(){

x 4


x 10


200


}

void fun(){


}



endl;endl;

2


endl;endl;}}

x 10

3



void main(){

x = 4;

x 4


x 10


201


}

void fun(){


}



endl;endl;

2


endl;endl;}}

x 10

4



void main(){

x = 4;

x 4


x 10


202


}

void fun(){


}



endl;endl;

2


endl;endl;}}

x 10

5



void main(){

x = 4;

x 4


203


}

void fun(){


}



endl;endl;

6



void main(){

x = 4;

x 4


204


}

void fun(){


}



endl;endl;

7

II. Using Parameters• Function Parameters come in three flavors:

–– Value parameters Value parameters – which copy the values of the function arguments

–– Reference parametersReference parameters – which refer to the function arguments by other local names and have the


205

arguments by other local names and have the ability to change the values of the referenced arguments

–– Constant reference parametersConstant reference parameters – similar to the reference parameters but cannot change the values of the referenced arguments

Person 21 (Jayadi Kasenda, Rizky Rajamuda,, Imelda Florensia)


206

Value Parameters• This is what we use to declare in the function signature or

function header, e.g.

int max (int x, int y);– Here, parameters x and y are value parameters– When you call the max function as max(4, 7)max(4, 7), the values 4 and 7 are


207

– When you call the max function as max(4, 7)max(4, 7), the values 4 and 7 are copied to x and y respectively

– When you call the max function as max (a, b),max (a, b), where a=40 and b=10, the values 40 and 10 are copied to x and y respectively

– When you call the max function as max( a+b, b/2),max( a+b, b/2), the values 50 and 5 are copies to x and y respectively

• Once the value parameters accepted copies of the corresponding arguments data, they act as local variables!

Example of Using Value Parameters and Global Variables

#include <iostream.h>int x; // Global variable// Global variablevoid fun(int x){

cout << x << endl;x=x+5;

x 0


208

x=x+5;}void main(){

x = 4;fun(x/2+1);cout << x << endl;

}


x = 4;x = 4;fun(x/2+1);fun(x/2+1);cout << x << cout << x <<

endl;endl;

1




x 4

void fun(int x void fun(int x


209

x=x+5;}void main(){


}



endl;endl;

2

void fun(int x void fun(int x )){ {

cout << x << cout << x << endl;endl;

x=x+5;x=x+5;}} 3

3




x 4

void fun(int x void fun(int x 38


210

x=x+5;}void main(){


}



endl;endl;

2



x=x+5;x=x+5;}}

3

4

8




x 4

void fun(int x void fun(int x 38


211

x=x+5;}void main(){


}



endl;endl;

2



x=x+5;x=x+5;}}

38

5




x 4


212

x=x+5;}void main(){


}



endl;endl;

6




x 4


213

x=x+5;}void main(){


}



endl;endl;

7

Reference Parameters

• As we saw in the last example, any changes in the value parameters don’t affect the original function arguments

• Sometimes, we want to change the values of the original function arguments or return with more


214

• Sometimes, we want to change the values of the original function arguments or return with more than one value from the function, in this case we use reference parameters– A reference parameter is just another name to the

original argument variable– We define a reference parameter by adding the & in

front of the parameter name, e.g.

double update (double & & x);

Example of Reference Parameters

#include <iostream.h>void fun(int &y){

cout << y << endl;


215

y=y+5;}void main(){

int x = 4; // Local variable// Local variablefun(x);cout << x << endl;

}


int x = 4;int x = 4;fun(x);fun(x);cout << x << cout << x <<

endl;endl;

1 x? x4



cout << y << endl;y=y+5;

}void fun( int & y void fun( int & y ))


216

}void main(){

int x = 4; // Local variablefun(x);cout << x << endl;

}



endl;endl;

2x? x4

)){ {

cout<<y<<endl;cout<<y<<endl;y=y+5;y=y+5;

}}

3






217

}void main(){


}



endl;endl;

2x? x4

)){ {


}}

4 9






218

}void main(){


}



endl;endl;

2x? x9

)){ {


}}

5




}


219

}void main(){


}



endl;endl;

6

x? x9




}


220

}void main(){


}



endl;endl;

x? x9

7

Constant Reference Parameters• Constant reference parameters are used under the

following two conditions:– The passed data are so big and you want to save time and

computer memory– The passed data will not be changed or updated in the

function body


221

function body• For example

void report (constconststring && prompt);• The only valid arguments accepted by reference

parameters and constant reference parameters are variable names– It is a syntax error to pass constant values or expressions to

the (const) reference parameters

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