This document discusses key concepts in C++ including classes, arrays of objects, reference variables, and dynamic memory allocation. It defines a Point class with x and y data members and input and output functions. It also shows how to create an array of objects of a class like Employee. Reference variables provide aliases for existing variables and are useful for passing arguments by reference. Dynamic memory is allocated at runtime using new and freed using delete. Multidimensional arrays require all dimensions except the first to be specified.

1. •A program with class
•A program with class
•Array of objects
•Concept of reference
•Dynamic memory allocation
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

2. A program with class
class point
{
int x,y; //data members by default private
public:
void input(int a, int b)
{
{
x=a;
y=b;
}
void output(void)
{
cout<<“x=”<<x<<“n”; //print value of x on output screen
cout<<“y=”<<y;
}
};
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

3. A program with class Cont..
int main()
{
point p1, p2; // object creation
p1.input(25,30);// member function calling
p2.input(55,60);
p1.output(); //print values of x and y for object p1
p1.output(); //print values of x and y for object p1
p2.output();
return 0;
}
Output:
x=25
y=30
x=55
y=60
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

4. Array of objects
 Array: Collection of elements of same data type.
 If elements are of class type, then it is called array of objects.
 Example-
class employee
{
{
char name[20];
int age;
public:
void getdata( );
void putdata( );
};
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

5. Array of objects
 Class “employee” used to create different categories of
employees. Example-
employee faculty[3]; // array of faculty
employee staff[5]; // array of staff
employee staff[5]; // array of staff
faculty[i].getdata(); // input data for ith faculty
staff[i].getdata(); // input data for ith staff
faculty[i]. putdata(); // display data of ith faculty
staff[i].putdata(); // display data of ith staff
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

6. Concept of reference variables
 provides an alias (alternative name) for a previously
defined variable.
 Syntax:
data_type & reference_name=variable_name;
data_type & reference_name=variable_name;
 Example-
int x = 10;
int & y = x; // y is reference variable for x;
 Both variables refer to the same memory location.
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

7. Concept of reference variables
cout<<x; // print 10
cout<<y; // print 10
x= x+5;
cout<<x; // print 15
cout<<x; // print 15
cout<<y; // print 15
y=0;
cout<<x; // print 0
cout<<y; // print 0
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

8. Application of reference variables
 In passing arguments to functions.
 Example-
void swap(int x, int y) //swap values of two variables
{ int t=x; x=y; y=t;}
{ int t=x; x=y; y=t;}
int main()
{
int a=5, b=10;
swap(a,b); // function call by value
cout<<a<<b; // print 5 and 10
return 0;
}
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

9. Application of reference variables
void swap(int &x, int &y) //swap values of two variables
{ int t=x; x=y; y=t;}
int main()
{
{
int a=5, b=10;
swap(a,b); // function call by reference
cout<<a<<b; // print 10 and 5
return 0;
}
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

10. Dynamic memory allocation
 Memory allocated at run-time.
 “new” operator for memory allocation
 “delete” operator to free the allocated memory
Syntax:
 Syntax:
pointer-variable = new datatype;
 Example-
int *p=new int; // allocate integer size memory
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

11. Dynamic memory allocation
 *p = 10; // assign value 10 to newly created
memory
 int *p=new int(10);// initialize the memory with value
10
10
 new can be used to create a memory space for any data
type including user defined such as arrays, structures,
and classes.
 int *p=new int[15];// creates memory for an array of 15
integer elements
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

12. Dynamic memory allocation
 For multi-dimensional arrays, all the array sizes must
be supplied.
 Example-
int *q=new int[5][3][4];// legal
int *q=new int[5][3][4];// legal
int *q=new int[m][3][4];// first dimension may be
variable, all other must be constant.
int *q=new int[5][3][ ];// illegal
int *q=new int[ ][3][4];// illegal
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

13. Dynamic memory allocation
 When allocated memory is no longer needed, it is
destroyed to release the memory space for reuse.
 Syntax-
delete pointer-variable;
delete pointer-variable;
 Example-
delete p; // free the memory pointed by pointer p.
delete [ ] q;// free the entire array pointed by pointer q.
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.

14. Thank You
Prepared by: Anil Kumar Tailor, Assistant Prof.,
Engineering College Ajmer.