C++ overview

DATA STRUCTURES &
ALGORITHMS
C++ WARM-UP
- PREM RANJAN

OUTLINE
• History and overview
• Basic features
• Parameter passing
• Classes
• Inheritance and virtual
• Header file
• IO
• Memory Management
• Big three: destructor, copy constructor, and assignment operator
• Const
• Template

HISTORY OF C++
• 1972: C language developed at Bell Labs
• Dennis Ritchie wrote C for Unix OS
• Needed C for work with Unix
• late 70s: C becomes popular for OS development by many vendors
• Many variants of the language developed
• ANSI standard C in 1987-89

HISTORY OF C++ (CONTINUED)
• early 80s: Bjarne Stroustrup adds OO features to C creating C++
• 90s: continued evolution of the language and its applications
• preferred language for OS and low level programming
• popular language for application development
• low level control and high level power

CONCEPTUALLY WHAT IS C++
• Alternatives:
• is it C, with lots more options and features?
• is it an OO programming language with C as its core?
• is it a development environment?
• On most systems it is a development environment, language, and library,
used for both procedural and object oriented programming, that can be
customized and extended as desired

VERSIONS OF C++
• ANSI C++
• Microsoft C++ (MS Visual C++ 6.0)
• Other vendors: Borland, Symantec, Turbo, …
• Many older versions (almost annual) including different version of C too
• Many vendor specific versions
• Many platform specific versions
• For this class: Unix / Linux based versions
• g++

CHARACTERISTICS OF C++ AS A COMPUTER
LANGUAGE
• Procedural
• Object Oriented
• Extensible
• ...

OTHER OO LANGUAGES
• Smalltalk
• pure OO language developed at PARC
• Java
• built on C/C++
• objects and data types
• Eifel and others

WHAT YOU CAN DO WITH C++
• Apps (standalone, Web apps, components)
• Active desktop (Dynamic HTML, incl Web)
• Create graphical apps
• Data access (e-mail, files, ODBC)
• Integrate components w/ other languages

DISADVANTAGES OF C++
• Tends to be one of the less portable languages
• Complicated?
• 40 operators, intricate precedence, pointers, etc.
• can control everything
• many exceptions and special cases
• tremendous libraries both standard, vendor specific, and available for
purchase, but all are intricate
• Aspects above can result in high maintenance costs

ADVANTAGES OF C++
• Available on most machines
• Can get good performance
• Can get small size
• Can manage memory effectively
• Can control everything
• Good supply of programmers
• Suitable for almost any type of program (from systems programs to
applications)

OUTLINE
• History and overview
• Basic features
• Parameter passing
• Classes
• Inheritance and virtual
• Header file
• IO
• Memory Management
• Big three: destructore, copy constructor, and assignment operator
• Const
• Template

PRIMITIVE TYPES
• bool true or false (only C++)
• char 8/16-bit
• short 16-bit signed integer
• int 32-bit signed integer
• unsigned 32-bit unsigned integer
• long 32 / 64-bit signed integer
• float 32-bit floating point
• double 64-bit floating point

OPERATORS AND PRECEDENCE
• [ ] .
• to access arrays elements / to access object methods and fields
• expr++ expr-- ++expr --expr !
• new (type)expr
• * / %
• + -
• << >> (integers only)
• < > >= <=
• == !=
• &

OPERATORS AND PRECEDENCE
• ^
• |
• && (booleans only)
• || (booleans only)
• ?:
• = += -= *= ….
• C++ allows operator overloading

PRECEDENCE EXAMPLE
• What is: 5 + 21 / 4 % 3
• = 5 + (21 / 4) % 3
• = 5 + ( 5 % 3)
• = 5 + 2
• = 7

EXPLICIT CASTING
• (type) expression
• Possible among all integer and float types
• Possible among some class references
• E.g. int i = (int) ( (double)5 / (double)3 )

IMPLICIT CASTING
• Applied automatically provided there is no loss of precision
• float  double
• int  double
• Example
• int iresult, i=3;
• double dresult, d=3.2;
• dresult = i/d => implicit casting dresult=0.9375
• iresult = i/d => error! Why? Loss in precision, needs explicit casting

CONTROL FLOW
if (boolean)
statement;
else if(boolean)
statement2;
else
statement3;
Booleans only, not integers!
• if (i > 0)  correct
• if (i = 2)  correct / incorrect ?

SWITCH / CASE
• switch (controlVar)
{
case 'a' :
statement-1
break;
case 'b' :
statement-2
break;
default :
statement-3
break;
}
• Do not forget the break command to avoid surprise result!

LOOPS
while(<boolean>)
statement;
do
statement;
while(<boolean>)
for(init-expr; <boolean>; incr-expr)
statement;

SOME CONVENTIONS FOR VARIABLE NAMES
• Use letters and numbers
• Do not use special characters including spaces, dots, underlines, pound signs,
etc.
• The first letter will be lower case
• Use variable names that are meaningful (except for occasional counters that
we might call i, j, x, etc.)
• You can concatenate words, and capitalize each after the first, e.g., bankBal,
thisAcctNum, totAmt
• If you abbreviate, be consistent. For example do not use both bankBal and
totalBalance as variable names.

SOME CONVENTIONS FOR STRUCT AND CLASS NAMES
• In creating names of structs and classes, apply the same rules
as for variable names, except the first character will be upper
case
• Example:
• an object's name: myCar
• the struct or class name: Car
• Another Example: aPerson and Person

PASSING PARAMETERS
• C++ allows for three different ways of passing parameters:
• Pass “by value”
• E.g. foo (int n)
• Appropriate for small objects (usually primitive types) that should
not be altered by the function call
• Pass “by constant reference”
• E.g. foo(const T& myT)
• Appropriate for large objects that should not be altered by the
function call
• Pass “by reference”
• E.g. foo(bool & errFlag)
• Appropriate for small objects that can be altered by the function call
• Array types are always passed “by reference”

PASSING BY VALUE
void square(int i)
{
i = i*i;
}
int main()
{
int i = 5;
square(i);
cout << i << endl;
}

PASSING BY REFERENCE
void square(int& i)
{
i = i*i;
}
int main()
{
int i = 5;
square(i);
cout << i << endl;
}

PASSING BY CONSTANT REFERENCE
void square(const int& i)
{
i = i*i;
}
int main()
{
int i = 5;
square(i);
cout << i << endl;
}
Wont work, why?

PASSING BY CONSTANT REFERENCE
int square(const int& i)
{
return i*i;
}
int main()
{
int i = 5;
cout << square(i) << endl;
}
Will it his work?

WHAT IS A REFERENCE?
• An alias – another name for an object.
int x = 5;
int &y = x; // y is a reference to x
y = 10;
• What happened to x?
• What happened to y? – y is x.

WHY ARE THEY USEFUL?
• When passing argument of large size (class type), can save space
• Sometimes need to change a value of an argument
• Can be used to return more than one value (pass multiple parameters by
reference)

HOW ARE REFERENCES
DIFFERENT FROM POINTERS?
Reference Pointer
int a = 10;
int b = 20;
int &c = a;
c = b;
What is the value of a?
int a = 10;
int b = 20;
int *c = &a;
c = &b;

CLASSES
• Provide a mechanism for defining classes of objects.
• We can define the class of all computers to have certain
characteristics.
• An instance of a computer is your home PC.
• Classes contain member variables and member
functions.

CLASSES IN C++:
WHY CREATE CLASSES / OBJECTS?
• Keeps all related info (i.e., data) together
• Refer to all the related info by one name
• Protect the information
• Hide methods that use or change the info
• Keep methods together with their related info

EXAMPLE OF BENEFITS OF CREATING AN OBJECT
• Keeps all related info (i.e., data) together
Person thisPerson;
Person thisPerson = new Person ("Bill", "Clinton", 52);
• Refer to all the related info by one name
thisPerson
• Protect the information
lastName = "Dole"; //normally data members
are private, and member functions are public

CLASSES AND OBJECTS
Mammals
Humans Tigers
Hank Peggy Tony
class
class
class
inherits inherits
instance-ofinstance-of

EXAMPLE OF A SIMPLE CLASS
class Change
{
private:
int quarters;
int dimes;
public:
int getQuarters() {return quarters;}
int getDimes() {return dimes;}
void setQuarters(int aQuarters) {quarters = aQuarters;}
…...
void printChange()
{cout << "nQuarters: " << quarters
<< " Dimes: " << dimes << endl;
}
};

MORE CLASS EXAMPLE
class human
{
// this data is private to instances of the class
int height;
char name[];
int weight;
public:
void setHeight(int heightValue);
int getHeight();
};

FUNCTION DEFINITIONS
void human::setHeight(int heightValue)
{
if (heightValue > 0)
height = heightValue;
else
height = 0;
}
int human::getHeight()
{
return(height);
}

EXAMPLE
// first we define the variables.
int height = 72;
int result = 0;
human hank;
//set our human’s height
hank.setHeight(height);
//get his height
result = hank.getHeight();
cout << “Hank is = “ << result <<
“inches tall” << endl;
Hank is 72 inches tall
Output

INSTANTIATING AN OBJECT
• The class definition does not create any objects
• Instantiating and constructing are equivalent words for building a
new object based on the model (i.e., template) of the class
• Instantiating is done just like declaring a variable of a built in data
type
• Instantiating is done by a constructor (sometimes called a
constructor method)
• If the "class provider" does not provide a constructor, then the C++ compiler
provides a default one automatically
• The default constructor does not provide values to the data members (i.e. the
instance variables)

INSTANTIATING AN OBJECT (MORE)
• When the object is instantiated, memory is allocated
• Example of instantiation (implicit call of constructor)
Car myCar;
Elephant oneElephant, twoElephant;
• No initialization takes place
• Each object has its own memory allocation
• oneElephant and twoElephant are separate objects in different locations in memory
• Each is addressed individually by name or location
• Each data member is addressed individually using the object name and the data
member name, for example:
oneElephant.age
twoElephant.name

REFERENCING AN OBJECT
• Each object has a name (or a location) which is assigned when the object is
instantiated
• private data members are accessible only within the class
• since most data members are private, that means that these data items are accessed
generally by means of member functions
• myElephant.age = 72; //won't work, assuming is declared as private
• myElephant.setAge(72); // will work

INHERITANCE
• The power of object-oriented languages
• Enables reuse of fields/methods
• All parent fields included in child instantiation
• Protected and public fields and methods directly accessible to child
• Parent methods may be overridden
• New fields and methods may be added to the child
• Multiple inheritance

INHERITANCE (CONT’D)
class classname: public parentname {
private:
….;
public:
….;
//access to parent methods through
// parentname::methodname …
}

HEADER FILE
• For complex classes, the member functions are declared in a header file and
the member functions are implemented in a separate file.
• This allows people to look at the class definitions, and their member functions separately
• The header file needs to be included in your program when you use the
classes defined in the head file

#include “Segment.H”
#include <iostream>
# INCLUDE
Insert header file at this point.
Use library header.

HEADER GUARDS
#ifndef __SEGMENT_HEADER__
#define __SEGMENT_HEADER__
// contents of Segment.H
//...
#endif
• To ensure it is safe to include a file more than once.

HEADER GUARDS
#ifndef __SEGMENT_HEADER__
#define __SEGMENT_HEADER__
// contents of segment.H
//...
#endif
• To ensure it is safe to include a file more than once.
If this variable is
not defined…Define it.
End of guarded area.

OUTPUT
#include<iostream>
Tell compiler that we are doing I/O
cout
Object to which we can send data.
<<
operator for sending data.
endl `n’ `t’
Special symbols that we can send.

FORMATTING OUTPUT
ios::left left justify the output
ios::right right justify the output
ios::scientific use scientific notation for numbers
ios::hex print numbers in hexadecimal base
ios::dec print numbers in decimal base
ios::uppercase print all characters in upper case
cout.setf(long flag) cout.unsetf(long flag)
Set different formatting
parameters for next output.
Disable these formatting
parameters.

EXAMPLE
#include<iostream.h>
main()
{
cout.width(10); //sets width to 10
cout << “hello” << endl;
cout.setf(ios::left);
cout << “hello” << endl;
cout << 16 << endl;
cout.setf(ios::hex, ios::basefield);
cout << 16 << endl;
}
hello
hello
16
10
Output

INPUT
#include <iostream.h>
Tell the linker we are doing basic I/O
cin
The input object. It retrieves input from the keyboard
>>
The extractor operator.

EXAMPLE
main ()
{
int userInput;
cout << “Enter number:”;
cin >> userInput;
cout << “You entered ” <<
userInput << endl;
}
Enter number:12345
You entered 12345
Output

I/O FROM A FILE
• I/O from a file is done in a similar way.
#include <fstream.h>
main()
{
int inputNumber;
ofstream myOutputFile(“outfile”);
ifstream myInputFile(“infile”);
myOutputFile << “text to file.” << endl;
myInputFile >> inputNumber;
myOutputFile.close();
myInputFile.close();
}

#include<string>
#include<fstream>
#include<iostream>
#include<iomanip>
using namespace std;
int main(int argc, char *argv[])
{
// Check input
if(argc<2)
{
cout<<"Usage: "<<argv[0]<<" <filename>"<<endl;
return 0;
}
// Try to read from file
cout<<"Reading tokens from file'"<<argv[1]<<"':"<<endl;
ifstream in(argv[1]);
if(!in)
cout<<" - Could not read from file '"<<argv[1]<<"'."<<endl;
else
{
string token;
cout.setf(ios::right);
for(unsigned i=1; in>>token; i++)
cout<<setw(4)<<i<<": "<<token<<endl;
}
in.close();
cout<<endl;
// Allow user to enter a token
string text;
cout<<"Enter sometext: ";
getline(cin, text);
// Append new tokensto file
ofstream out(argv[1], ios::app);
if(out)
out<<endl<<text<<endl;
else
cout<<"- Could not writeto file'"<<argv[1]<<"'"<<endl;
out.close();
return 0;
}
This program reads a file
name given by the user and
the read token by token from
the file. The tokens are
printed to the standard
output.
The second half of the
algorithm reads a token from
a standard input and appends
it to the file that was given.

WHAT IS A POINTER?
int x = 10;
int *p;
p = &x;
p gets the address of x in memory.
p
x10

WHAT IS A POINTER?
int x = 10;
int *p;
p = &x;
*p = 20;
*p is the value at the address p.
p
x20

WHAT IS A POINTER?
int x = 10;
int *p;
p = &x;
*p = 20;
Declares a pointer
to an integer
& is address operator
gets address of x
* dereference operator
gets value at p

A POINTER EXAMPLE
int main(){
int i, j;
int *pi, *pj;
i = 5;
j = i;
pi = &i;
pj = pi;
*pj = 4;
cout << i << “ “;
cout << j << “ “;
cout << *pi << “ “;
cout << *pj << endl;
return 0;
}
> 4, 5, 4, 4

ALLOCATING MEMORY USING NEW
Point *p = new Point(5, 5);
• Point is a class already defined
• new can be thought of a function with slightly strange syntax
• new allocates space to hold the object.
• new calls the object’s constructor.
• new returns a pointer to that object.

MEMORY ALLOCATION EXAMPLES
• new returns a pointer to the dynamically created object.
#include “Cow.h”
#include <iostream>
int main(){
int *i = new int(12);
Cow *c = new Cow;
...
delete i;
delete c;
return 0;
}

PROBLEMS
• Dangling pointers
• Pointers to memory that has already been deallocated
• segmentation fault (core dump)... or worse....
• Memory leak
• Loosing pointers to dynamically allocated memory
• Substantial problem in many commercial products
• See Windows 98
• C++ HAS NO GARBAGE COLLECTION!

DANGLING POINTER EXAMPLES
int main(){
int *myNum = new int(12);
int *myOtherNum = myNum;
delete myNum;
cout << *myOtherNum << endl;
return 0;
}
int* badFunction(){
int num = 10;
return &num;
}
int* stillBad(int n){
n += 12;
return &n;
}
int main(){
int num = 12;
int *myNum = badFunction();
int *myOtherNum = stillBad(num);
cout << *myNum << “, “;
cout << *myOtherNum << endl;
return 0;
}

MEMORY LEAK EXAMPLES
int main(){
int *myNum = new int(12);
myNum = new int(10);
// Oops...
delete myNum;
return 0;
}
int evilFunction(){
int *i = new int(9);
return *i;
}
int main(){
int num = evilFunction();
// I’m loosing my memory!!
return 0;
}

DEALLOCATING MEMORY USING DELETE
// allocate memory
Point *p = new Point(5, 5);
...
// free the memory
delete p;
For every call to new, there must be
exactly one call to delete.

USING NEW WITH ARRAYS
int x = 10;
int* nums1 = new int[10]; // ok
int* nums2 = new int[x]; // ok
• Initializes an array of 10 integers on the heap.
• C++ equivalent of C
int* nums = (int*)malloc(x * sizeof(int));

USING NEW WITH MULTIDIMENSIONAL ARRAYS
int x = 3, y = 4;
int* nums3 = new int[x][4][5];// ok
int* nums4 = new int[x][y][5];// BAD!
• Initializes a multidimensional array
• Only the first dimension can be a variable. The rest must be constants.
• Use single dimension arrays to fake multidimensional ones

USING DELETE ON ARRAYS
// allocate memory
int* nums1 = new int[10];
int* nums3 = new int[x][4][5];
...
// free the memory
delete[] nums1;
delete[] nums3;
• Have to use delete[].

CLASS DESTRUCTORS
• If a class dynamically
allocates memory, we
need a way to deallocate it
when it’s destroyed.
• Distructors called upon
distruction of an object
class MyClass{
public:
MyClass(){
// Constructor
}
~MyClass(){
// Destructor
}
...
};

DESTRUCTORS
• delete calls the object’s destructor.
• delete frees space occupied by the object.
• A destructor cleans up after the object.
• Releases resources such as memory.

DESTRUCTORS – AN EXAMPLE
class Segment
{
public:
Segment();
virtual ~Segment();
private:
Point *m_p0, *m_p1;
};

DESTRUCTORS – AN EXAMPLE
Segment::Segment()
{
m_p0 = new Point(0, 0);
m_p1 = new Point(1, 1);
}
Segment::~Segment()
{
delete m_p0;
delete m_p1;
}

COPY CONSTRUCTOR AND ASSIGNMENT OPERATOR
• Copy Constructor:
class Rooster{
public:
...
Rooster(const Rooster &rhs){
// Do your deep copy
}
...
};
...
// Usage
Rooster r(12);
Rooster s(r);
• Assignment Operator:
class Rooster{
public:
...
Rooster&
operator=(const Rooster &rhs){
// Copy stuff
}
...
};
...
// Usage
Rooster r(12), s(10);
r = s;

CANONICAL FORM
• All classes should have
each of the following:
• Default constructor
• Copy constructor
• Assignment operator
• Destructor
// Canonical Cow
class Cow{
public:
Cow(){...}
Cow(const Cow &rhs){...}
Cow& operator=(const Cow &c)
{...}
~Cow(){...}
...
};

INTRODUCING: CONST
void Math::printSquare(const int& i)
{
i = i*i;
cout << i << endl;
}
int main()
{
int i = 5;
Math::printSquare(i);
Math::printCube(i);
}
Won’t compile.

HOW DOES CONST WORK HERE?
void Math::printSquares(const int& j, int& k)
{
k = k*k; // Does this compile?
cout << j*j << “, “ << k << endl;
}
int main()
{
int i = 5;
Math::printSquares(i, i);
}

RETURNING CONST REFERENCES IS OK
class Point
{
point:
const double& getX() const;
const double& getY() const;
void move(double dx, double dy);
private:
double m_x, m_y;
}
const double& Point::getX()
const
{
return m_x;
}
Constant function,
also called accessor
Return a reference to a
constant double

NAMESPACES
• Namespaces are kind of like packages in Java
• Reduces naming conflicts
• Most standards C++ routines and classes and under the std
namespace

USING NAMESPACE
#include <iostream>
...
std::string question =
“How do I prevent RSI?”;
std::cout << question << std::endl;
string answer = “Type less.”;
cout << answer << endl;
But, not in header files!

TEMPLATE
What exactly are templates for, and why learn them?
• Limited Generic Programming (polymorphism)
Some functions have the same semantic meaning for some (if not all) data
types. For instance, a function print() should display a sensible
representation of anything passed in. Ideally, it shouldn’t need to be
rewritten for each possible type.
• Less repetitive code
Code that only differs in the data type it handles does not have to be
rewritten for each and every data type you want to handle. It’s easier to
read and maintain since one piece of code is used for everything

EXAMPLE: A SWAP FUNCTION
Naive method – write an overloaded function for each type
void swap(int &a, int &b) {
int c = a;
a = b;
b = c;
}
void swap(T &a, T &b) {
T c = a;
a = b;
b = c;
}
Swap for integers Swap for an arbitrary type T
template <typename T>
T c = a;
a = b;
b = c;
}
This function can be used with any
type that supports assignment and can
be passed in as a non-const reference.
Problem: Oftentimes, it is nice to be able to swap the values of two
variables. This function’s behavior is similar for all data types. Templated
functions let you do that – in most cases without any syntax changes.
Template method – write one templated function

TEMPLATE SYNTAX: SWAP DISSECTED
T c = a;
a = b;
b = c;
}
The template<…> line states that
everything in the following
declaration or definition is under
the subject of the template. (In this
case, the definition is the function
swap)
In here goes a list of “placeholders
variables.” In almost all cases, they
will be specified with either the
typename or class keywords.
These two keywords are
equivalent.
“Placeholder variables” have one value
within each template declaration. Think of
them as being replaced by whatever type
you specify the template to be.

TEMPLATE SYNTAX: USING IT
T c = a;
a = b;
b = c;
}
Example:
double d1 = 4.5, d2 = 6.7;
swap(d1, d2);
Syntax

CLASS TEMPLATES: EXAMPLE
Example: A templated, dynamic, 2 dimensional array (Matrix)*
#ifndef MATRIX_H
#define MATRIX_H
class Matrix {
public:
Matrix(int rows, int cols);
Matrix(const Matrix &other);
virtual ~Matrix();
Matrix& operator=(const Matrix &rhs);
T* operator[](int i);
int getRows() const;
int getCols() const;
protected:
void copy(const Matrix &other);
private:
Matrix();
int m_rows;
int m_cols;
T *m_linArray;
};
#endif /* MATRIX_H */
File: Matrix.h
Notice the only addition to
the class definition is the
line:
Within the the
definition block,
the placeholder
has can be used as
a data type. When
the template is
specialized, it
takes on the value
of the
specialization.

T* Matrix<T>::operator[](int i) {
return m_linArray + (i*m_cols);
}
void
Matrix<T>::copy(const Matrix &other) {
m_rows = other.m_rows;
m_cols = other.m_cols;
int size = m_rows * m_cols;
m_linArray = new T[size];
for( int i=0; i < size; i++ ) {
m_linArray[i] =
other.m_linArray[i];
}
}
int Matrix<T>::getRows() const {
return m_rows;
}
int Matrix<T>::getCols() const {
return m_cols;
}
CLASS TEMPLATES: EXAMPLE CONT’D
#include "Matrix.h"
Matrix<T>::Matrix()
{}
Matrix<T>::Matrix(int rows, int cols) {
m_rows = rows;
m_cols = cols;
m_linArray = new T[m_rows * m_cols];
}
Matrix<T>::Matrix(const Matrix &other) {
copy(other);
}
Matrix<T>::~Matrix() {
delete[] m_linArray;
}
Matrix<T>&
Matrix<T>::operator=(const Matrix &other) {
if( this != &other ) {
delete[] m_linArray;
copy(other);
}
return *this;
} File: Matrix.cc

Matrix<T>&
Matrix<T>::operator=(const Matrix &other) {
if( this != &other ) {
this->~Matrix();
copy(other);
}
return *this;
}
CLASS TEMPLATES: MEMBER FUNCTIONS DISSECTED
Again, a templated class name by itself
has no meaning (eg. Matrix by itself
means nothing). It only gets meaning
through specialization, explicit or implicit.
Thus, when referring to an instance of a
templated class (a specific specialization),
the class name must be explicitly
specialized.
Here, the template has been
implicitly specialized by its context.
It is within the specialization region
of the class scope. Thus it does not
need the template arguments. For a
class definition, the specialization
region is the class block.
specialization region of
Matrix<T>::
Notice that the
specialization
region does not include the
return type. Thus the return
type needs explicit
specialization
This may be
obvious, but
remember that
though constructors
and destructors
have the same name
as a the class
template, they are
functions and do not
need to be
specialized.

CLASS TEMPLATES: USAGE
•Templated classes must be explicitly specialized. Thus, to create a 2
dimensional Matrix of doubles using the last example, the syntax would be:
Matrix<double> m(3,3);
Syntax

STL
• Allows you to easily store anything without writing a container yourself
• Will give you the most hideous compile errors ever if you use them
incorrectly.

STL EXAMPLE
typedef list<int> intlist;
typedef intlist::iterator intlistIter;
intlist v;
v.push_back(4);
intlistIter a;
for(a = v.begin(); a != v.end(); ++a)
{
int c = (*a);
}

• Now compile and run a simple c++ program

COMPILATION MODEL
• Preprocessor
• Resolves all preprocessor directives
• #include, #define macros, #ifdef, etc.
• Compiler
• Converts text into object files
• May have unresolved interobject references
• Linker
• Resolves all interobject references (or gives you a linker error)
• Creates the binary executable
• Loader
• Loads the program into RAM and runs the main() function

COMPILATION
Preprocessor
Inlines #includes etc.
Compiler
Translates to machine code
Associates calls with functions
Linker
Associates functions with definitions
Object files
Executable
External Libraries, libc.so, libcs123.so

HELLOWORLD.CPP
#include <iostream> // For cout
int main(){
cout << "Hello World!" << endl;
return 0;
}

COMPILING WITH G++
ix$ ls
hello.cpp
ix$ ls
hello.cpp
ix$ g++ hello.cpp
ix$ ls
a.out* hello.cpp
ix$ g++ -c hello.cpp
ix$ ls
a.out* hello.cpp hello.o
ix$ g++ -o hello hello.cpp
ix$ ./hello
Hello World!

SIMPLE MAKEFILE
All: hello
hello: hello.o
g++ -o hello hello.o
hello.o: hello.cpp
g++ -c hello.cpp

ix$ ls
hello.cpp makefile
ix$ make
g++ -c hello.cpp
g++ -o hello hello.o
ix$ ls
hello* hello.cpp hello.o makefile
ix$ ./hello
Hello World!

C++ overview

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