Pointers 1. Introduction Declaring pointer variables Pointer operators Pointer arithmetic 2 Topics to be Covered.

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Presentation transcript:

Pointers 1

Introduction Declaring pointer variables Pointer operators Pointer arithmetic 2 Topics to be Covered

Pointers in C++ is a very powerful programming technique. It is very useful in: ◦ To call functions using “Pass-by-Reference” technique ◦ Dynamic memory ◦ Improve the efficiency of functions ◦ Develop dynamic data structures, such as binary trees and linked lists etc. 3 Introduction

A pointer is a variable that holds a memory address. This address is the location of another variable in memory. 4 Introduction contd. 10 int count 0X10012 Variable Name Memory Address Value Stored at the Memory address 0X10012 int *count_ptr 0X10014 A normal variable A pointer variable

In spite of the powerfulness pointers are very dangerous as well. ◦ Programs with pointers can go wrong very easily. ◦ Programmers often make lot of mistakes in manipulating pointers. Due to this reason new languages such as Java had eliminated ‘Pointer’ concept altogether. 5 Introduction contd.

Like the normal variables, pointer variables must be declared before use. Pointers are denoted using the sign * Examples: ◦ int *count_ptr – A pointer to an integer variable ◦ float *avg_ptr – A pointer to a floating point variable ◦ char *choice_ptr - A pointer to a character variable 6 Declaring a Pointer Variable

Initially when you declare a pointer variable it will be NULL ◦ The pointer dose not point to any object. 7 Declaring a Pointer Variable contd. NULL int *count_ptr 0X10014 Variable Name Memory Address Value Stored at the Memory address

There are two types of pointer operators. 8 Pointer Operators OperatorMeaningDescription &Address of operator Returns the memory address of a variable *Dereferencing operator Returns the value stored at the location pointed by a pointer

Example 1.int marks; 2.int *marks_ptr; 3.marks = 30; 4.marks_ptr = &marks; We can use & operator to initialize a pointer variable 9 The Address of Operator - & int marks 0X10034 int *marks_ptr 0X X

Example 1.int marks, value; 2.int *marks_ptr; 3.marks = 30; 4.marks_ptr = &marks; 5.value = *marks_ptr; 10 The Dereferencing Operator - * int marks 0X10034 int *marks_ptr 0X X int value 0X

The Dereferencing Operator is useful when we want to access and modify the actual content of the variable which is pointed by a pointer. 11 The Dereferencing Operator contd.

What is the result of the following code ? int number; int *number_ptr; number = 30; number_ptr = &number; *number_ptr = 50; cout<<“number = ”<<number”; 12 Pointer Operators - Exercise number = 50

What is the result of the following code ? int number; int *number1_ptr; int *number2_ptr; number = 30; number1_ptr = &number; number2_ptr = number1_ptr; *number2_ptr = 10; cout<<"number =“<<number; 13 Pointer Operators - Exercise number = 10

What is the result of the following code ? int number1 = 10; int number2 = 20; int *number1_ptr; int *number2_ptr; number1_ptr = &number1; number2_ptr = &number2; *number2_ptr = *number1_ptr; * number1_ptr = 50; cout<<"number1 = “<<number1; cout<<”number2 = “<<number2; 14 Pointer Operators - Exercise number1 = 50 number2 = 10

Thank you. 15