12438 18Types Pointers

7/29/2019 12438 18Types Pointers

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Types of Pointers


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Pointer Arithmetic

Various operations: -

Addition of a number to a pointer variable.

Subtraction of a number from a pointervariable.

Subtraction of one pointer variable from

another.


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Addition of a number to apointer variable

Suppose p is a pointer variable pointing to an

element of integer type, then the statement

p++; or ++p;

increments the value of p by a factor of 2.

This increment factor will be 1 for char, 4 forlong int, & 8 for long float.


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Subtraction of a number froma pointer variable

Suppose p is a pointer variable pointing to an

element of integer type, then the statement

p--; or --p;

decrements the value of p by a factor of 2.


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Subtraction of one pointervariable from another

One pointer variable can be subtracted from

another provided both point to the same data

type.

Operations on pointers are not permitted:-

Addition of two pointer variables.

Multiplication of a pointer variable by a number.

Division of a pointer variable by a number.


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Pointer to a Pointer

We can have a variable that holds an

address of a variable that in turn holds an

address of another variablepointer to a

pointer or double indirection.

Declaration: -

int **ptr;


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Pointers to Functions

Used in C++ for dynamic binding, & event

based applications.

Known as callback function

. Using it, we can allow a C++ program to

select a function dynamicallyat run time.

We can also pass a function as an argument

to another function. Function is passed as a

pointer.


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Contd

Two types of function pointers: -

Point to static member functions

Point to non-static member functions

These two function pointers are incompatible

with each other.

2nd type requires hidden argument.

Syntax: - data_type(*function_name) ();


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Example:

typedef void (*FunPtr) (int, int);

void Add (int i, int j){ cout


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This Pointer

C++ uses a unique keyword called thisto represent

an object that invoked a member function.

All non-static member functions of an object have

access to a special pointer named this. The this pointer hold the address of the object

whose member function is invoked.

It is not a part of an object.

It is passed as an implicit first argument to every

non-static member function.


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Example:-class sample

{ int a, b;

public:void showAddress()

{ cout


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Dynamic Memory Management

C++ provides a set of operators, calleddynamic memory management operators,to allocate & de-allocate memory at execution

time, i.e. dynamically. The memory allocated dynamically, must be

de-allocated before your program finishes itsexecution.

If you run the same program many times,many users are using your programconcurrently, the OS may run out of memory.


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New Operator

Allocates the memory & always returns a

pointer to an appropriate type.

Syntax: -

type * new type [size in integer];

Example: -

int *intPtr;intPtr = new int [100];


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Contd

It permits the initialization of memory locationsduring allocation.

Syntax: -

type *ptrVar = new type (IntialValue);

Example: - int *intPtr = new int (100);

This statement allocates memory for an integernumber & initializes it with value 100. The addressof the memory allocated memory is assigned topointer variable intPtr.


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Delete Operator

A counterpart of new operator & it de-

allocates memory allocated by the new

operator back to the free poll of memory.

Syntax: -

delete ptrVar;


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Thank You!!!

12438 18Types Pointers

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