Pointers in C++: Declaration, Initialization and Advantages

Pointers in C++: An Overview

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What are Pointers in C++?

Pointers are variables that contain the memory address of another variable instead of a direct value. Such variables can be of type int, float, char, etc. By referencing this memory address, programmers can access and modify data indirectly.

Use of pointers in C++

• Dynamic memory allocation - In the C++ programming language, the programmers can dynamically allocate memory by using the malloc() and calloc() functions particularly where the pointer is used. This is the primary use of pointers in C++
• Arrays, Functions, and Structures - Pointers in the c ++ programming language are widely used in arrays, structures, and functions. It reduces the code and improves the performance of that particular program.

Pointer Declaration in C++

We do not initialize the pointer; we simply declare it using the * (asterisk symbol) before a pointer's name or after the data type.

Syntax

• datatype *var_name;

• datatype* var_name; //preferred syntax
  

Example

• int *a;//pointer to int 

• int* a;//pointer to int 

Pointer Initialization in C++

Example

#include <iostream>
using namespace std;

int main() {
 int x = 42; // Declare and initialize an integer variable 'x'
 
 // declare pointer variable 'ptr' and initialize it with the address of 'x'
 int *ptr = &x; 

 // print value of x
 cout << "x = " << x << endl;
 
 // print address of x
 cout << "Address of x (&x) = " << &x << endl
 << endl;

 // print pointer ptr
 cout << "ptr = " << ptr << endl;

 // print the content of the address ptr points to
 cout << "Content of the address pointed to by ptr (*ptr) = " << *ptr << endl;
 
 return 0;
}

In this C++ code,

• an integer variable, x is initialized to 42
• a pointer, ptr is created to hold x's address in memory.

Output

x = 42
Address of x (&x) = 0x7ffeb5f7b3c4

ptr = 0x7ffeb5f7b3c4
Content of the address pointed to by ptr (*ptr) = 42

* used in the above example can confuse you. It serves two purposes:

• When used in declaration (int *a), it creates a pointer variable.
• When not used in declaration (*a), it act as a dereference operator.

Modifying Values Pointed by Pointers

Example

 #include <iostream>
using namespace std;

int main() {
 int x = 42; // Declare and initialize an integer variable 'x'
 
 // declare pointer variable 'ptr' and initialize it with the address of 'x'
 int *ptr = &x; 

 // print value of x
 cout << "x = " << x << endl;

 // print *ptr
 cout << "*ptr = " << *tr << endl
 << endl;

 cout << "Changing value of x to 70:" << endl;

 // change value of x to 70
 x = 70;

 // print x
 cout << "x = " << x << endl;

 // print *ptr
 cout << "*ptr = " << *ptr << endl
 << endl;

 cout << "Changing value of *ptr to 60:" << endl;

 // change value of ptr to 60
 *ptr = 60;

 // print x
 cout << "x = " << x << endl;

 // print *ptr
 cout << "*ptr = " << *ptr << endl;
 return 0;
}

In the above C++ code, ptr points to the address of x. Therefore

• when value of x is changed, *ptr also gets changed
• when *ptr is modified, value of x also gets modified

Output

x = 42
*ptr = 42

Changing value of x to 70:
x = 70
*ptr = 70

Changing value of *ptr to 60:
x = 60
*ptr = 60

Read more: Call by Value and Call by Reference in C++

Advantages of using Pointers in C ++

• Pointers help to reduce the code and improve the performance of the program. It mainly assists in retrieving trees, strings, and many more. Pointers are primarily used with arrays, functions, and structures.
• The programmer or user can return multiple values from a particular function with the help of the pointer
• Pointers help users access any memory location in the memory of the computer.

Summary