Learn c++ Programming Language

The C++ Language
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Overview of ‘C++’
• Bjarne Stroupstrup, the language’s creator
• C++ was designed to provide Simula’s facilities for program organization
together with C’s efficiency and flexibility for systems programming.
• Modern C and C++ are siblings

Outline
• C++ basic features
– Programming paradigm and statement syntax
• Class definitions
– Data members, methods, constructor, destructor
– Pointers, arrays, and strings
– Parameter passing in functions
– Templates
– Friend
– Operator overloading
• I/O streams
– An example on file copy
• Makefile

C++ Features
• Classes
• User-defined types
• Operator overloading
• Attach different meaning to expressions such as a + b
• References
• Pass-by-reference function arguments
• Virtual Functions
• Dispatched depending on type at run time
• Templates
• Macro-like polymorphism for containers (e.g., arrays)
• Exceptions

Compiling and Linking
• A C++ program consists of one or more source files.
• Source files contain function and class declarations and definitions.
– Files that contain only declarations are incorporated into the source files that
need them when they are compiled.
• Thus they are called include files.
– Files that contain definitions are translated by the compiler into an intermediate
form called object files.
– One or more object files are combined with to form the executable file by the
linker.

A Simple C++ Program
#include <cstdlib>
#include <iostream>
using namespace std;
int main ( ) {
intx, y;
cout << “Please enter two numbers:”;
cin >> x >> y;
int sum = x + y;
cout << “Their sum is “ << sum << endl;
return EXIT_SUCCESS;
}

The #include Directive
• The first two lines:
#include <iostream>
#include <cstdlib>
incorporate the declarations of the iostream and cstdlib libraries into the
source code.
• If your program is going to use a member of the standard library, the
appropriate header file must be included at the beginning of the source
code file.

The using Statement
• The line
tells the compiler to make all names in the predefined namespace std
available.
• The C++ standard library is defined within this namespace.
• Incorporating the statement
is an easy way to get access to the standard library.
– But, it can lead to complications in larger programs.
• This is done with individual using declarations.
using std::cin;
using std::cout;
using std::string;
using std::getline;

Compiling and Executing
• The command to compile is dependent upon the compiler and operating
system.
• For the gcc compiler (popular on Linux) the command would be:
– g++ -o HelloWorld HelloWorld.cpp
• For the Microsoft compiler the command would be:
– cl /EHsc HelloWorld.cpp
• To execute the program you would then issue the command
– HelloWorld

C++ Data Type
• Basic Java types such as int, double, char have C++ counterparts of the
same name, but there are a few differences:
• Boolean is bool in C++. In C++, 0 means false and anything else means
true.
• C++ has a string class (use string library) and character arrays (but they
behave differently).

Constants
• Numeric Constants:
• 1234 is an int
• 1234U or 1234u is an unsigned int
• 1234L or 1234l is a long
• 1234UL or 1234ul is an unsigned long
• 1.234 is a double
• 1.234F or 1.234f is a float
• 1.234L or 1.234l is a long double.
• Character Constants:
• The form 'c' is a character constant.
• The form 'xhh' is a character constant, where hh is a hexadecimal digit, and hh is between 00
and 7F.
• The form 'x' where x is one of the following is a character constant.
• String Constants:
• The form "sequence of characters“ where sequence of characters does not include ‘"’ is called a
string constant.
• Note escape sequences may appear in the sequence of characters.
• String constants are stored in the computer as arrays of characters followed by a '0'.

Operators
• Bitwise Operators
• ~ (complement)
• & (bitwise and)
• ^ (bitwise exclusive or)
• | (bitwise or)
• << (shift left)
• >> (shift right)
• Assignment Operators
• +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=
• Other Operators
• :: (scope resolution)
• ?: (conditional expression)
• stream << var
• stream >> exp

Increment and Decrement
• Prefix:
– ++x
• x is replaced by x+1, and the value is x+1
– --x
• x is replaced by x-1, and the value is x-1
• Postfix:
– x++
• x is replaced by x+1, but the value is x
– x--
• x is replaced by x-1, but the value is x

Object-Oriented Concept (C++)
• Objects of the program interact by sending messages to each other

Basic C++
• Inherit all C syntax
– Primitive data types
• Supported data types: int, long, short, float, double, char,
bool, and enum
• The size of data types is platform-dependent
– Basic expression syntax
• Defining the usual arithmetic and logical operations such as
+, -, /, %, *, &&, !, and ||
• Defining bit-wise operations, such as &, |, and ~
– Basic statement syntax
• If-else, for, while, and do-while

Basic C++ (cont)
• Add a new comment mark
– // For 1 line comment
– /*… */ for a group of line comment
• New data type
– Reference data type “&”. Much likes pointer
int ix; /* ix is "real" variable */
int & rx = ix; /* rx is "alias" for ix */
ix = 1; /* also rx == 1 */
rx = 2; /* also ix == 2 */
• const support for constant declaration, just likes C

Class Definitions
• A C++ class consists of data members and methods (member functions).
class IntCell
{
public:
explicit IntCell( int initialValue = 0 )
: storedValue( initialValue ) {}
int read( ) const
{ return storedValue;}
void write( int x )
{ storedValue = x; }
private:
int storedValue;
}
Avoid implicit type conversion
Initializer list: used to initialize the data
members directly.
Member functions
Indicates that the member’s invocation does
not change any of the data members.
Data member(s)

Information Hiding in C++
• Two labels: public and private
– Determine visibility of class members
– A member that is public may be accessed by any method in any class
– A member that is private may only be accessed by methods in its class
• Information hiding
– Data members are declared private, thus restricting access to internal
details of the class
– Methods intended for general use are made public

Constructors
• A constructor is a special method that describes how an
instance of the class (called object) is constructed
• Whenever an instance of the class is created, its constructor is
called.
• C++ provides a default constructor for each class, which is a
constructor with no parameters. But, one can define multiple
constructors for the same class, and may even redefine the
default constructor

Destructor
• A destructor is called when an object is deleted either
implicitly, or explicitly (using the delete operation)
– The destructor is called whenever an object goes out of scope or is
subjected to a delete.
– Typically, the destructor is used to free up any resources that were
allocated during the use of the object
• C++ provides a default destructor for each class
– The default simply applies the destructor on each data member. But
we can redefine the destructor of a class. A C++ class can have only
one destructor.
– One can redefine the destructor of a class.
• A C++ class can have only one destructor

Constructor and Destructor
class Point {
private :
int _x, _y;
public:
Point() {
_x = _y = 0;
}
Point(const int x, const int y);
Point(const Point &from);
~Point() {void}
void setX(const int val);
void setY(const int val);
int getX() { return _x; }
int getY() { return _y; }
};

Constructor and Destructor
Point::Point(const int x, const int y) : _x(x), _y(y) {
}
Point::Point(const Point &from) {
_x = from._x;
_y = from._y;
}
Point::~Point(void) {
/* nothing to do */
}

C++ Operator Overloading
class Complex {
...
public:
...
Complex operator +(const Complex &op) {
double real = _real + op._real,
imag = _imag + op._imag;
return(Complex(real, imag));
}
...
};
In this case, we have made operator + a member of class
Complex. An expression of the form
c = a + b;
is translated into a method call
c = a.operator +(a, b);

Operator Overloading
• The overloaded operator may not be a member of a class: It can rather
defined outside the class as a normal overloaded function. For
example, we could define operator + in this way:
class Complex {
...
public:
...
double real() { return _real; }
double imag() { return _imag; }
// No need to define operator here!
};
Complex operator +(Complex &op1, Complex &op2)
{
double real = op1.real() + op2.real(),
imag = op1.imag() + op2.imag();
}

Friend
• We can define functions or classes to be friends of a class
to allow them direct access to its private data members
class Complex {
...
public:
...
friend Complex operator +(
const Complex &,
const Complex &
);
};
Complex operator +(const Complex &op1, const Complex &op2) {
double real = op1._real + op2._real,
imag = op1._imag + op2._imag;
}

Standard Input/Output Streams
• Stream is a sequence of characters
• Working with cin and cout
• Streams convert internal representations to character streams
• >> input operator (extractor)
• << output operator (inserter)

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Learn c++ Programming Language

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