Table of Contents
C++ Pointer and This Pointer
Pointer
- Pointer is a memory variable that stores a memory address.
- Pointer can have any name that is legal to other variable.
- It can be declared like normal variable it is always denoted by star(*)operator
- C++ variables are used to hold data during program execution.
- Every variable can occupy some memory location to hold the data.
- Memory is arranged in a sequence of byte.
- The number specification to each byte is called memory address.
- The sequence starts from 0 onwords.
- It is possible to access and display the address of memory location using the pointer variable.
Feature of pointer
- Pointer saves memory space.
- Execution time with pointer is faster.
- The memory is accessed efficiently with the pointer.
- Pointers are used with data structure and they are useful for representing two dimensional array.
- A pointer declared to a base class can access the object of derived class.
Pointer Declaration
Pointer can be declared as follows:
Syntax:
Data type * pointer variable name.
Example:
int *a;
int *b;
float*c;
- It inform to the compiler that hold the address of any variable.
- The in-direction (*) operator is also called de-reference operator.
- Whereas a pointer indirectly access to their own values.
- The (&) is the address operator represented the address of a variable.
- The address of any variable is a whole number.
Example:
Display the value and address of the variable using pointer.
#include<iostream.h>
#include<conio.h>
void main()
{
int *p;
int x=10;
p=&x;
cout<<x<<&x;
cout<<*p<<&p;
}
Void pointer
- Pointer can be also be declared as void type.
- Void pointer cannot be reference without explicit type conversion.
- A void pointer can pointer any type of variable with proper type casting.
Example:
#include<iostream.h>
#include<conio.h>
int p;
float d;
char c;
void *pt=&p;
void main()
{
*(int*)pt=12;
cout<<p;
pt=&d;
*(float*)pt=5.4;
cout<<d;
pt=&c;
*(char*)pt=’x’;
cout<<c;
}
Pointer to class
- The pointer is a variable that hold the address of another data variable.
- The variable may be of int, float and double in the same way we can define pointer to class.
- This type of pointer is called class pointers.
Syntax:
Class name *pointer variable name
Example:
Student *str;
Example:
#include<iostream.h>
#include<conio.h>
Class man
{
public:
char name[20];
int age;
void getdata(char s[10], int a)
{
name = s;
age = a;
}
Void putdata()
{
cout<<name<<age;
}
};
Void main()
{
man *ptr, m;
ptr = &m;
ptr->getdata(“xyz”,m);
ptr->putdata();
}
Pointer to object
- Like variable object can also have an address.
- The pointer can point to a specified object.
- Using the pointer it is possible to access different type of classes.
Syntax:
Class name *ptr variable name;
Example:
Student *str;
Example:
#include<iostream.h>
#include<conio.h>
class bill
{
intqty;
float price;
float amount;
public:
Void getdata (int a, float b, float c)
{
qty = a;
price = b;
amount = c;
}
Void show()
{
cout<<”QUANTITY:”<<qty<<”\n”;
cout<<”PRICE”<<price<<”\n”;
cout<<”AMOUNT”<<amount<<”\n”;
}
};
Int main()
{
clrscr();
bill s;
bill *ptr;
ptr=&s;
ptr->getdata(45,10.25,45*10.25);
(*ptr).show();
return 0;
}
This pointer
- The objects are used to invoke non static member function of the class.
- The pointer this is transferred as an unseen parameters to call non static member function.
- The keyword “this” is a local variable always present in the body of non-static member function.
- The keyword this does not need to be declared.
- The pointer is rarely referred explicitly in a member function.
- It is used implicitly with in the function for member reference.
- Using this pointer it is possible to access the individual member variables of the object.
Example:
Program to use this pointer and return pointer reference (minimum or smallest value of two numbers)
#include<iostream.h>
#include<conio.h>
Class number
{
Public: intnum;
void input()
{
cin>>num;
}
void show()
{
cout<<num;
}
number min(number t)
{
If(t.num<num)
Return t;
else
return *this;
}
};
Void main()
{
number n, n1, n2;
n1.input();
n2.input();
n=n1.min(n2);
n.show();
}
Pointer to derived classes and base class
- It is possible to declare a pointer, which points to the base class as well as the derived class.
- One pointer can point different classes.
Example:
Write a program to declare a pointer to the base class and access the member variable of base and derived class.
#include<iostream.h>
#include<conio.h>
class A
{
public:
int b;
void display()
{
cout<<<”b=”<<b<<”\n”;
}
};
Class B:public A
{
Public:
Int d;
Void display()
{
cout<<”b=”<<”\n”<<”d=”<<d<<”\n”;
}
};
void main()
{
clrscr();
A *CP;
A base;
CP=&base;
CP->b=100;
//CP->d=200; Not accessible
cout<<”\n CP points to the base object\n”;
CP->display();
B b;
cout<<”\n CP points to the derived class \n”;
CP=&b;
CP->b=150;
//CP->d=300; Not Accessible
CP->display();
return 0;
}
Pointer to the derived class
#include<iostream.h>
#include<conio.h>
class A
{
public:
int b;
void display()
{
cout<<”b=”<<b<<”\n”;
}
};
Class B : public A
{
Public:
int d;
void display()
{
cout<<”\t b=”<<”\n”<<”\t d=”<<d<<”\n”;
}
};
Void main()
{
clrscr();
B*CP;
B b;
CP=&b;
CP->b=100;
CP->d=350;
cout<<”\n CP points to the derived object \n”;
cout<<display();
return 0;
}
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