The document discusses constructors and destructors in C++ classes. It provides examples of constructor definitions and errors. It explains the purpose and behavior of default, parameterized, and copy constructors. It also discusses the characteristics and purpose of constructors and destructors.

1. CONSTRUCTOR
AND
DESTRUCTOR

2. 1. Point out the errors, if any, in the following program.
class date
{
private:
int day,month,year;
date()
{
day = 2;
month = 10;
year = 2008;
}
};
void main()
{
date today;
}

3. Error :
The default constructor is defined
under private section; so it is not
accessible in function main( ).

4. 2. Point out the errors, if any, in the following program.
class value
{
private:
int i;
float f;
public:
value()
{
i = 0;
f = 0.0;
return 1;
}
};
void main()
{
value vi;
}

5. Error :
The constructor should not return
any value. Here constructor
contains return statement.

6. 3. Read the following code segment.
#include <iostream.h>
class sample
{
int x, y;
public:
sample(int a = 10, int b = 20)
{
x = a;
y = b;
}
void show()
{
cout << “n x = “ << x << “y = “ << y;
}
};
void main()
{
sample s1;
sample s2(4);
sample s3 = sample(6,8);
s1.show();
s2.show();
s3.show();
}
Explain the working of constructor for the creation of each object.
What will be the output of the above code.

7. b) x = 10, y=20
x = 4, y=20
x = 6, y=8

8. 4. A class named employee is having the
following constructors.
i) employee();
ii) employee(int, float);
iii) employee(employee &f);
A) Name the category to which each
constructor belongs.
B) Write down the purpose of each.
C) Define the destructor for this class.

9. 1. i) default constructor,
ii) parameterized constructor,
iii) copy constructor
2. short note about default constructor,
parameterized constructor and copy
constructor
3. ~employee( ) { }

10. 5. The following code defines a class for finding out the area of a circle.
#include<iostream.h>
class circle
{
float rad;
public:
circle(float x)
{
rad = x;
}
void area()
{
cout << 3.14 * rad * rad;
}
};
void main()
{
circle(5.5).area();
}
What is the purpose of the statement in the main function?
What is the output?

11. a)Through this statement, an
anonymous object (temporary instance)
is created and initialized with the value
5.5 and that object calls the member
function area( )
b) 94.985

12. 6. While declaration, initialization is
possible with variables, arrays and
structures. What about of classes?
Justify your answer.
• But an object of a class cannot be initialized
in similar fashion because the access labels
restrict the accessibility of the data members.

13. 7. A constructor is usually defined
in public section. Why?
• Generally a constructor is defined under the
public section of a class so that its objects can
be created in any function.

14. 8. Is constructor definition
compulsory? Give justification to
support your answer.
• Yes, constructor definition is compulsory. A
Constructor is defined like other member
functions of a class. It can be defined either
inside or outside the class specification.

15. 9. List down the characteristics of
constructors.
• They should be declared in the public section.
• They are invoked automatically when the
objects are created.
• They do not have return types, not even void
and therefore, and they cannot return values.
• They cannot be inherited.
• Like other C++ functions, they can have default
arguments.
• They cannot be virtual.
• We cannot refer to their addresses.
• They cannot be static.

16. 10. List down the characteristics of
destructors.
• They are invoked automatically when the
objects are destroyed.
• They obey the usual access rules that other
member functions do.
• They cannot be inherited.
• No argument can be provided to a destructor,
neither does it return any value.
• They cannot be virtual.
• We cannot refer to their addresses.
• They cannot be static.
• If there is no destructor in a class, a default
destructor is generated by the compiler.