array of objects slides.pdf

•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.

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;
}
};

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

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( );
};

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

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.

Concept of reference variables
cout<<x; // print 10
cout<<y; // print 10
x= x+5;
cout<<y; // print 15
y=0;
cout<<x; // print 0
cout<<y; // print 0

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 main()
{
int a=5, b=10;
swap(a,b); // function call by value
cout<<a<<b; // print 5 and 10
return 0;
}

Application of reference variables
void swap(int &x, int &y) //swap values of two variables
int main()
{
{
int a=5, b=10;
swap(a,b); // function call by reference
cout<<a<<b; // print 10 and 5
return 0;
}

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

 *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

 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

 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.

Thank You

array of objects slides.pdf

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