4. A First C++ Program
#include <iostream>
using namespace std;
// main() is where program execution begins
int main() {
// prints Hello World
cout << "Hello World";
return 0;
}
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5. A First C++ Program
• Save the program as first.cpp
• Build and Run the code
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6. Another C++ Program
#include <iostream>
using namespace std;
int main() {
int num;
cin >> num;
cout << "number: " <<num << endl;
return 0;
}
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7. The General Form of a Class in C++
A class is defined by specifying the data and the
code that operate on the data
The general form:
class classname{
private data and functions declarations
access-specifier:
data and functions declarations
access-specifier:
data and functions declarations
};
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9. The General Form of a Class in C++
• Functions that are declared within a class are
called member functions
• Member functions may access any element of the
class of which they are a part, this includes all
private elements
• Variables that are elements of a class are called
member variables or data members. (The term
instance variable is also used)
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10. Access specifier
• access-specifier is one of these three C++ keywords:
– public
– private
– Protected
• (access-specifier is also known as visibility label)
• By default, functions and data declared within a class
are private to that class and may be accessed only by
other members of the class
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11. Access specifier
The public access-specifier allows functions or data
to be accessible to other parts of your program
The protected access-specifier is needed only when
inheritance is involved
Once an access-specifier has been used, it remains in
effect until either another access-specifier is
encountered or the end of the class declaration is
reached
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12. Access specifier
• In general, you should make all data members of a
class private to that class.
– This is part of the way that encapsulation is achieved
• However, there may be situations in which you will
need to make one or more variables public
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13. Creating Objects
Once a class has been declared, we can create
variables (object) of that type by using the class
name (like any other built in variables)
The necessary memory space is allocated to an
object at this stage
Class specification provides only a template and
does not create any memory space for the members
Format: class_name object_name;
Example: person p;
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14. Creating Objects
Objects can also be created when a class is defined
by placing their names immediately after the closing
brace.
class class_name
{
} x, y, z;
Each object contains its own copy of each instance
variables defined by the class
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15. Accessing class members
The private data of a class can only be
accessed only through the member functions
of that class
Following is the format for accessing a
member
Object_name.function_name(arguments)
Object_name.variable_name
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16. Defining member functions
Member functions can be defined in two
places:
Outside the class definition
Inside the class definition
Irrespective of the place of definition, the
function will perform the same task
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17. Outside the class definition
Member functions that are only declared inside of a
class, have to be defined separately outside the class
General format of a member function definition outside
the class is
return_type class_name:: function_name (arguments)
{
}
The membership label class_name:: tells the compiler
that, function function_name belongs to the class
class_name
The symbol :: is called the scope resolution operator
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18. Inside the class definition
Another method of defining a member function is to
replace the function declaration by the actual
function definition inside the class definition
Usually, only small functions are defined inside the
class definition
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19. General structure of a c++ program
Include files
Class declarations
Member functions definitions
Main function program
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