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<h3 class="pb-3 pt-3">C++ Memory Management</h3>

<p>C++ allows us to allocate the memory of a variable or an array in run time. This is known as Dynamic Memory Allocation.But before understanding

the term called Dynamic Memory Location let us understand the meaning

of Dynamic .In programming the word Dynamic refers to run time.So the

term Dynamic Memory Location means allocating memory at run time.On

the other hand if you look at the other languages such as Java , Python

the compiler automatically manages the memories allocated to variables. But this is not the case in C++.In C++, we need to deallocate the

dynamically allocated memory manually after we have no use for the

variable.We can allocate and then deallocate memory dynamically using

operators called new and delete.</p>

<hr/>

<h4 class="pt-3 pb-3">Types of Memory Allocation</h4>

<ol>

<li>Compile time (Static) Memory Allocation.</li>

<li>Run time (Dynamic) Memory Allocation.</li>

</ol>

<ol>

<li><strong>Compile time Memory Allocation:-</strong>If the compiler is able to

determine the number of bytes required for a variable or array by looking at its

declaration then we say that it is Static or Compile time Memory Location.<br><br>

For Example:1. int a; // this line clearly indicates that variable a will require 2 or 4 bytes.<br><br>

Example: 2. int arr[10]; // this line also clearly indicates that the array will require20 or 40 bytes.<br><br>

Thus both the above declaration are called Static Memory Location.</li><br>

<li><strong>Run time Memory Allocation</strong>If the memory required by the

variable or array is calculated at run time then such allocation is called as Dynamic

Memory Allocation.We use the kind of memory allocation to create arrays of user

defined size and these arrays are called as Dynamic Arrays.</li>

</ol>

<ul>

<li><strong>Code Segment:-</strong>In code segment executive code along with Compiled program are

kept . It is read only. Code segment are kept below the stack and heap in order to avoid

over writing.</li>

<li><strong>Data Segment:-</strong>Static and Global variables are kept inside the Data Segment.</li>

<li><strong>Stack:-</strong>Stack is basically restricted form of Array. In this memory diagram is opened

from the single end only and data are arranged and accessed in sequential manner. The

stack is LIFO based which means Last In First Out. Each new variable is pushed into the

stack. Once the variable get pop out memory get free. Once a stack variable is free, that

region of memory becomes available for another variables. In that way stack grows and

shrinks as functions push and pop local variables. It stores local data, return addresses, arguments passed to functions and current status of memory.Index is also considered as

very important part of the Stack . It tells capacity of stack.</li>

<li><strong>Heap:-</strong>Memory is allocated during program execution. Memory is allocated using new

operator and deallocating memory using delete operator.</li>

</ul>

<hr/>

<h4 class="pt-3 pb-3">Allocation of Heap Memory using New Keyword</h4>

<p><strong>Syntax:</strong></p>

<p><strong>Data_type pointername = <code>new</code> data_type</strong></p><br>

<p><strong>For example:</strong></p>

<pre>int *new_op = new int; // allocating block of memory

int *new_op = new int[ 5 ];</pre>

<p>If enough amount of memory is not available in heap so it is indicated by throwing an

exception of type <code>std::bad_alloc</code> and a pointer is returned.</p>

<hr/>

<h4 class="pt-3 pb-3">Deallocation of memory using Delete Keyword</h4>

<p>Once heap memory is allocated to a variable or class object using the <strong>new</strong> keyword, we can

deallocate that memory space using the <strong>delete</strong> keyword.It return the memory to the

Operating System. This is Known as the Memory Deallocation.</p>

<p><strong>Syntax:</strong></p>

<p><code>delete</code> <strong>pointervariable</strong></p><br>

<p><strong>Consider the code:</strong></p>

<pre>// declare an int pointer

int* pointVar;

// dynamically allocate memory// for an int variable

pointVar = new int;

// assign value to the variable memory

*pointVar = 20;

// print the value stored in memory

cout << *pointVar; // Output: 20

// deallocate the memory

delete pointVar;</pre>

<p>Here, we have dynamically allocated memory for an <strong>int</strong> variable using the

pointer <code>pointvar</code>.After printing the contents of <code>pointvar</code>, we deallocated the memory

using delete</p>

<hr/>

<h5 class="pt-3 pb-3">Example 1: Dynamic Memory Allocation</h5>

<pre>#include <iostream>using namespace std;

int main()

{

// declare an int pointer

int* pointInt;

// declare a float pointer

float* pointFloat;

// dynamically allocate memory

pointInt = new int;

pointFloat = new float;

// assigning value to the memory

*pointInt = 20;

*pointFloat = 20.20f;

cout << *pointInt << endl;

cout << *pointFloat << endl;

// deallocate the memory

delete pointInt, pointFloat;

return 0;

}

Output</pre>

<h5 class="pt-3 pb-3">Output:</h5>

<pre>20

20.20</pre>

<p>In this program, we dynamically allocated memory to two variables of int and float types. After allocting the values to them and printing them, we finally deallocate the memories

using the code.</p>

<pre>delete pointInt, pointFloat;</pre>

<p><strong>Note:</strong>Dynamic memory allocation can make memory management more

efficient.Especially for arrays, where a lot of the times we don't know the size of the

array until the run time.</p>

<h5 class="pt-3 pb-3">Example 2: New and Delete Operator for Arrays</h5>

<pre>// C++ Program to store GPA of n number of students and display it// where n is the number of students entered by the user

#include <iostream>

#include <cstring>

using namespace std;

int main()

{

int number;

cout << "kindly enter total number of students: ";

cin >> number;

float* ptr;

// memory allocation of num number of floats

ptr = new float[number];

cout << "Kindly enter GPA of students." << endl;

for (int i = 0; i < number; ++i) {

cout << "Student" << i + 1 << ": ";

cin >> *(ptr + i);

}

cout << "\nShowing GPA of students." << endl;

for (int i = 0; i < number; ++i) {

cout << "Student" << i + 1 << " :" << *(ptr + i) << endl;

}

// ptr memory is released

delete [] ptr;

return 0;

}</pre>

<h5 class="pt-3 pb-3">Output:</h5>

<pre>Kindly enter total number of students: 10

Kindly enter GPA of students.

Student1: 3.6

Student2: 3.1

Student3: 3.9

Student4: 2.9

Student5: 3.0

Student6: 4.0

Student7: 3.3

Student8: 2.6

Student9: 3.5

Student10: 3.2

Showing GPA of students.

Student1 :3.6

Student2 :3.1

Student3 :3.9

Student4 :2.9

Student5 :3.0

Student6 :4.0

Student7 :3.3

Student8 :2.6

Student9 :3.5

Student10 :3.2</pre>

<p>In the above program, we have asked from the user to enter the number of students and

store it in the number variable.Then, we have allocated the memory dynamically for

the float array using new.We enter data into the array (and later print them) using pointer

notation.After we no longer need the array, we deallocate the array memory using the

code delete [ ] ptr; .Notice the use of [ ] after delete. We use the square brackets [ ] in

order to denote that the memory deallocation is that of an array.</p>

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