an introduction to c++ a first look. void functions #include #include void main( ) { cout

An Introduction to C++An Introduction to C++

A First LookA First Look

void Functionsvoid Functions

#include <iostream.h>#include <iostream.h>

void main( )void main( ){{

cout << “Hello world” << endl;cout << “Hello world” << endl;

}}

void Functionsvoid Functions


void main()void main(){{

cout << “Hello world” << endl;cout << “Hello world” << endl;

}}

Hello worldHello world

program executionprogram execution

Input and OutputInput and Output

The term The term stream stream refers to the abstract model of anrefers to the abstract model of aninput or output device in which the input device input or output device in which the input device produces a stream of characters and an output produces a stream of characters and an output device receives a stream of characters.device receives a stream of characters.

#include <#include <iostream.hiostream.h>> cin and cout are defined cin and cout are defined

#include <#include <fstream.hfstream.h>> files may be created/, modified & deletedfiles may be created/, modified & deleted

StreamsStreams

C++ programmers say that the output operation C++ programmers say that the output operation ‘‘inserts’ characters into an output streaminserts’ characters into an output stream

<< insertion operator<< insertion operator

The input operation ‘extracts’ characters The input operation ‘extracts’ characters from an input stream.from an input stream.

>> >> extraction operatorextraction operator

cin, coutcin, cout

cout cout <<<< “Enter a word: “; “Enter a word: “;cin cin >>>> aword; aword;

cout cout <<<< “Thanks for entering “ << aword ; “Thanks for entering “ << aword ;cout cout <<<< endl; endl;

<< insertion operator<< insertion operator>> >> extraction operatorextraction operator

Functions that return thingsFunctions that return things


int main( )int main( ){{

int number;int number;

cout << “Enter a number : “;cout << “Enter a number : “;cin >> number;cin >> number;cout << “Thanks for “ << number << endl;cout << “Thanks for “ << number << endl;

return 0;return 0;}}

Functions that return thingsFunctions that return things


int main()int main(){{

int number;int number;

cout << “Enter a number : “;cout << “Enter a number : “;cin >> number;cin >> number;cout << “Thanks for “ << number << endl;cout << “Thanks for “ << number << endl;


Enter a number: 10Enter a number: 10Thanks for 10Thanks for 10

program executionprogram execution

C++ built-in DatatypesC++ built-in Datatypes

int int (e.g. -6)(e.g. -6)

long long (e.g. 40000)(e.g. 40000)

floatfloat (e.g. -8.4)(e.g. -8.4)

double double (e.g. 3.14)(e.g. 3.14)

boolbool (e.g. true)(e.g. true)

charchar (e.g. ‘a’)(e.g. ‘a’)

C++ built-in DatatypesC++ built-in Datatypes

int int (e.g. -6)(e.g. -6)

long long (e.g. 40000)(e.g. 40000)

floatfloat (e.g. -8.4)(e.g. -8.4)

double double (e.g. 3.14)(e.g. 3.14)

boolbool (e.g. true)(e.g. true)

charchar (e.g. ‘a’)(e.g. ‘a’)

Used on AP examsUsed on AP exams

Other Datatypes implemented using ClassesOther Datatypes implemented using Classes

apstring name; apstring name; (e.g. “Smith”)(e.g. “Smith”)

apvector<int> Aapvector<int> A (e.g. integer arrays)(e.g. integer arrays)

apmatrix<int> A apmatrix<int> A (e.g. multi-dimensional arrays)(e.g. multi-dimensional arrays)

BigInt number BigInt number (e.g. 999999999)(e.g. 999999999)

apstack<int> Aapstack<int> A (e.g. stacks)(e.g. stacks)

apqueue<int> Aapqueue<int> A (e.g. queues)(e.g. queues)AB Exam OnlyAB Exam Only

PreprocessorPreprocessor

pre-processor commands begin with pre-processor commands begin with ## pre-processor commands are serviced pre-processor commands are serviced

first by the pre-processor which occurs first by the pre-processor which occurs before compilationbefore compilation

PreprocessorPreprocessor

#include is a pre-processor directive which #include is a pre-processor directive which inserts the contents of the file into the inserts the contents of the file into the current filecurrent file• #include <iostream.h>#include <iostream.h>

– angle brackets indicate to get the *.h file from a angle brackets indicate to get the *.h file from a previous defined ‘header directory’, which is known previous defined ‘header directory’, which is known to the environmentto the environment

• #include “apstring.h” #include “apstring.h” – double quotes mean that the file to merge in, is double quotes mean that the file to merge in, is

found in current directoryfound in current directory

Preprocessor...Preprocessor...

#ifndef #ifndef _DICE_H _DICE_H#define _DICE_H#define _DICE_H

..

..

..#endif#endif

The above technique is standard practice for most headerThe above technique is standard practice for most headerfiles. IFNDEF ensures that the code sandwiched betweenfiles. IFNDEF ensures that the code sandwiched betweenIFNDEF and ENDIF, will not be seen by the compiler if the IFNDEF and ENDIF, will not be seen by the compiler if the symbol symbol _DICE_H _DICE_H has already been defined. This has already been defined. This trick ensures that this code is only given once to the compiler.trick ensures that this code is only given once to the compiler.

Function PrototypesFunction Prototypes

A function’s prototype is the first line of the functionA function’s prototype is the first line of the function

void GetPayment (double amt)void GetPayment (double amt){{

}}


The compiler needs the function The compiler needs the function prototype for each function made prototype for each function made available to it, available to it, unless unless the function the function has been defined prior to its use.has been defined prior to its use.


Library functions have their prototypes defined Library functions have their prototypes defined within ‘header files’ located at the top of most C++within ‘header files’ located at the top of most C++programs.programs.

#include <math.h>#include <math.h>#include <iostream.h>#include <iostream.h>

void main()void main(){{

}}

/* math.h standard header *//* math.h standard header */#ifndef __MATH_H#ifndef __MATH_H#define __MATH_H#define __MATH_H

/* float declarations *//* float declarations */float cos(float x);float cos(float x);float sin(float x) ;float sin(float x) ;float tan(float x);float tan(float x);

#endif#endif

Inside .... Inside .... #include <math.h> #include <math.h>

Parameter PassingParameter Passing

pass by VALUEpass by VALUE• int SQUARED ( int N );int SQUARED ( int N );• function SQUARED ( N : integer) : integer;function SQUARED ( N : integer) : integer;

pass by REFERENCEpass by REFERENCE• int SQUARED ( int & N);int SQUARED ( int & N);• function SQUARED (var N : integer) : integer;function SQUARED (var N : integer) : integer;

pass by CONSTANT REFERENCEpass by CONSTANT REFERENCE• int SQUARED (const int & N);int SQUARED (const int & N);

ExampleExample

Write a C++ main program which asks Write a C++ main program which asks the user to enter an integer called, ‘N’.the user to enter an integer called, ‘N’.

Output the absolute value of N by Output the absolute value of N by writing a function called, writing a function called, ABSOLUTE(N).ABSOLUTE(N).

Sample Session:Sample Session: Enter N: -9Enter N: -9

Absolute Value = 9Absolute Value = 9

SolutionSolution #include <iostream.h>#include <iostream.h>

int ABSOLUTE( int N);int ABSOLUTE( int N);

int main()int main(){{ int N ; int N ; cout << “Enter N: “ ; cout << “Enter N: “ ; cin >> N;cin >> N; cout << “Absolute Value = “ cout << “Absolute Value = “ << ABSOLUTE(N) << endl;<< ABSOLUTE(N) << endl;


SolutionSolution

int ABSOLUTE( int N);int ABSOLUTE( int N);{{

int value=N;int value=N;

if (value < 0) if (value < 0) value = -1 * value;value = -1 * value;

return value;return value;}}

ConstantsConstants

#define MAXWORDS 1000#define MAXWORDS 1000

OR BETTER .... TO DOOR BETTER .... TO DO

const int MAXWORDS = 1000;const int MAXWORDS = 1000;

ConditionsConditions

If ( numA == numB)If ( numA == numB)numC = numA;numC = numA;

elseelsenumC = numB;numC = numB;

== == equalsequals!= != not equal tonot equal to< < less thanless than> > greater thangreater than<= <= less than orless than or equal toequal to>= >= greater thangreater than or equal toor equal to&& && ANDAND|| || OROR

ExerciseExercise

Write a C++ program which constructs Write a C++ program which constructs 3 double variables called, ‘X’ , ‘Y’ & ‘Z’.3 double variables called, ‘X’ , ‘Y’ & ‘Z’.

Output the middle number of ‘X’, ‘Y’ & ‘Z’.Output the middle number of ‘X’, ‘Y’ & ‘Z’.

Sample Session:Sample Session: Enter x: 6Enter x: 6

Enter y: 5Enter y: 5Enter z: 7Enter z: 7The middle number is 6The middle number is 6

SolutionSolution#include <iostream.h>#include <iostream.h>

int main()int main(){{ double x, y, z, sum, highest, lowest, middle; double x, y, z, sum, highest, lowest, middle;

cout << “Enter x: “ ; cout << “Enter x: “ ; cin >> x;cin >> x;cout << “Enter y: “ ; cout << “Enter y: “ ; cin >> y;cin >> y;cout << “Enter z: “’cout << “Enter z: “’ cin >> z;cin >> z;sum = x + y + z;sum = x + y + z;

highest = x;highest = x; //Determine highest//Determine highestif (y > highest) highest = y;if (y > highest) highest = y;if (z > highest) highest = z;if (z > highest) highest = z;

lowest = x;lowest = x; //Determine lowest//Determine lowestif (y < lowest) lowest = y;if (y < lowest) lowest = y;if (z < lowest) lowest = z;if (z < lowest) lowest = z;

middle = sum - highest - lowest;middle = sum - highest - lowest;cout << “The middle number is “ << middle;cout << “The middle number is “ << middle;return 0;return 0;

}}

ClassesClasses

Classes are objects with behavioursClasses are objects with behaviours

DICE CLASSDICE CLASS

ObjectObject RedRed

BehavioursBehaviours Roll()Roll() NumSides()NumSides() NumRolls()NumRolls()

ClassesClasses

Classes are objects with behavioursClasses are objects with behaviours

DICE CLASSDICE CLASS

ObjectObject RedRed

BehavioursBehaviours Roll()Roll() NumSides()NumSides() NumRolls()NumRolls()

Member FunctionsMember Functionsa Red diea Red die

The Dice ClassThe Dice Class#include <iostream.h>#include <iostream.h>#include “dice.h”#include “dice.h”

int main( )int main( ){{ int g, r, totalrolls;int g, r, totalrolls;

Dice red(6), green(6);Dice red(6), green(6);

g = green.Roll( );g = green.Roll( ); // Roll the Dice// Roll the Dicer = red.Roll( );r = red.Roll( );totalrolls = red.NumRolls( ) + green.NumRolls( );totalrolls = red.NumRolls( ) + green.NumRolls( );

cout << “Sum: “ << g + r << endl;;cout << “Sum: “ << g + r << endl;;cout << “Total : “ << totalrolls << endl;cout << “Total : “ << totalrolls << endl;return 0;return 0;

}}

ExerciseExercise

Write a C++ program which constructs Write a C++ program which constructs 5 red dice with names, 5 red dice with names, r1, r2, r3, r4 & r5.r1, r2, r3, r4 & r5.

Construct an integer variable called, Construct an integer variable called, ‘‘points’ and initialize it to 0.points’ and initialize it to 0.

Roll the 5 dice once! If a Yahtzee occursRoll the 5 dice once! If a Yahtzee occursincrement the points variable by 50.increment the points variable by 50.

SolutionSolution#include <iostream.h>#include <iostream.h>#include “dice.h”#include “dice.h”

int main( )int main( ){{ int points=0;int points=0;

Dice r1(6), r2(6), r3(6), r4(6), r5(6);Dice r1(6), r2(6), r3(6), r4(6), r5(6);int a = r1.Roll( ); int b = r2.Roll( );int a = r1.Roll( ); int b = r2.Roll( );int c = r3.Roll( );int c = r3.Roll( ); int d = r3.Roll( );int d = r3.Roll( );int e = r5.Roll( );int e = r5.Roll( );

if ((a==b) && (a==c) && (a==d) &&if ((a==b) && (a==c) && (a==d) && a==e))a==e))

points = points + 50;points = points + 50;

cout << points;cout << points;return 0;return 0;

}}

an introduction to c++ a first look. void functions #include #include void main( ) { cout

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