'this' pointer is a constant pointer that holds the memory address of the current object. .It identifies the currently calling object.It is useful when the argument variable name in the member function and the data member name are same.
#include< iostream >
using namespace std;
class T
{
public:
int x;
Void foo( )
{
x = 6;           // same as this->x = 6;
this- > x=5;  // explicit use of this->
cout < < endl < < x < < " "< < this- >x;
}
void foo(int x) //parameter x shadows the member with the same name
{
this->x = x;   // unqualified x refers to the parameter. 'this->' required for disambiguation
cout < < endl < < x < < " "< < this ->x;
}};
int main ( )
{
T tl, t2;
t1.foo();
t2.foo();
}
Output
5 5
5 5
---------------------------------------
Process exited after 0.1 seconds with return value 0
Press any key to continue ....

Whenever an object of a class is declared as a member of another class it is known as a container class. In the container-ship the object of one class is declared in another class.
Illustration: C++ program to illustrate the containership
#include < iostream >
using namespace std;
class outer
{
int date;
public:
void get ( );
};
class inner
{
int value;
outer ot;
//object ot of class outer is declared in
class inner
public;
void getdata( );
};
void outer::get( )
{
cout << "\nEnter a value";
cin >> data;
cout << "\nThe given value is" << data;
}
void inner:: getdata( )
{
cout << "\nEnter a value";
cin >> value;
cout << "\nThe given value is " << value;
ot.get( ); //calling of get( ) of class outer in getdata( )of class inner
}
int main ( )
{
inner in;
in.getdata( );
return( );
}
Output:
Enter a value 10
To given value is 10
 Enter a value 20
The given value is 20

When an object is passed by value the function creates its own copy of the object and works on it. Therefore any changes made to the object inside the function do not affect the original object.
C++ program to illustrate how the pass by value method work.
#include < iostream >
using namespace std;
class Sample
{
private:
int num;
public:
void set(int x)
{
num = x;
}
void pass(Sample obj 1, Sample obj 2)
{
obj 1.num= 100;
obj 2.num=200;
cout << "\n\n Changed value of object1 "<< obj 1.num;
cout << "\n\n Changed value of object1 "<< obj 2.num;
}
void print ( )
{
cout << num;
}
};
int main ( )
{
Sample s1;
Sample s2;
Sample s3;
s1.set(10);
s2.set(20);
cout << "\n\t\tExample program for pass by value \n\n\n";
cout << "\n\n Value of object1 before passing;s1.print( );
cout << "\n\n Value of object2 before passing";
s2.print( );
s3.pass(s1,s2);
cout << "\n\n Value of object1 after passing";
s1.print( );
cout << "\n\n Value of object2 after passing";
s2.print ( );
return ( );
}
Output:
Example program for PASS BY VALUE
Value of object 1before passing 10
Value of object 2 before passing 20
Changed value of object 1 100
Changed value of object 200
Value of object 1 after passing 10
Value of object 1 after passing 20

BACDBE
~E~B~D~C~A~B

(i) Hierarchical Inheritance
(ii) 41 Bytes
(ill) Price, SDName, Weight
(iv) DInput(), DShow( ), EDInput ( ), EDshow( ).

Digital signature:
(i) Digital signatures are based on asymmetric cryptography and can provide assurances of evidence to origin, identity and status of an electronic document, transaction or message, as well as acknowledging informed by the signer.
(ii) To create a digital signature, signing software (email) Creates a one-way hash of the electronic data to be signed.
(iii) The user's private key to encrypt the hash, returning a value that is unique to the hashed data. The encrypted hash, along with other information such as the hashing algorithm, forms the digital signature. Any change in the data, even to a single bit, results in a different hash value.

(iv) This attribute enables others to validate the integrity of the data by using the signer's public key to decrypt the hash. If the decrypted hash matches a second computed hash of the same data, it proves that the data hasn't changed since it was signed.
(v) If the two hashes don't match, the data has either been tampered with in some way (indicating a failure of integrity) or the signature-was created with a private key that doesn't correspond to the public key presented by the signer (indicating a failure of authentication).

#include < iostream.h >
using namespace std;
int main( )
{
float pi = 3.14, radius, height, CSA;
cout << "\n Curved Surface Area of a cylinder";
cout << "\n Enter Radius (in em): ";
cin >> radius;
cout << "\n Enter Height (in em): ";
cin >> height;
CSA = (2*pi*radius)*height;
system("cls");
cout << "\n Radius: " << radius <<" em ";
cout << "\n Height: " << height c << " em ";
cout << "\n Curved Surface Area of a Cylinder is " << CSA << " sq.cm ";
}

Operator	Operation	Example (Assume n=2; what will be value of n)
		Prefix	Postfix
++	Increment	++n;	n++;
		n=n+1; Value of n;	Value of n; n=n+1;
		Value of n = 3	Value of n = 2
--	Decrement	--n;	n--;
		n=n-1; Value of n;	Value of n; n=n-1;
		Value of n = 1	Value of n = 2

Nested class: When one class become the member of another class then it is called Nested class and the relationship is called containership.
Classes can be nested in two ways.
1. By defining a class within another class
2. By declaring an object of a class as a member to another class.
Defining a class with in another: When a class is declared with in another class, the inner class is called as Nested class (ie the inner class) and the outer class is known as Enclosing class. Nested class can be defined in private as well as in the public section of the Enclosing class.
C++ program to illustrate the nested class
#include < iostream >
using namespace std;
class enclose
{
private:
int x;
class nest
{
private:
int y;
public:
int z;
void prn ( )
{
y=3;z=2;
cout << "\n The product of'" << y << '*' << z << "=" << y*z << "\n";
}
}; //inner class definition over
nest n1;
public:
nest n2;
void square ( )
{
n2.prn ( ); //inner class member function is called by its object
x=2;
n2.z=4;
cout << "\n The product of " << n2.z << '*' << n2.
z << "=" << n2.z*n2.z << "\n";
cout << "\n The product of " << x << '*' << x << "=+ << x*x;
}
}; //outer class definition over
int main ( )
{
enclose e;
e.square ( ); // outer class member function is called
}
Output:
The product of 3*2=6
The product of 4*4=16
The product of 2*2=4
In the above program the inner class nest is defined inside the outer class enclose. nest is accessed by enclose by creating an objec of nest.

Re-usability: "Write once and use it multiple times" you can achieve this by using class.
Redundancy: Inheritance is the good feature for data redundancy, If you need a same functionality in multiple class you can write a common class for the same functionality and inherit that class to sub class.
Easy Maintenance: It is easy to maintain and modify existing code as new objects can be created with small difference to existing ones.
Security: Using data hinding and abstraction only necessary data will be provided thus maintains the security of data.

#incluede< iostream >
using namespace std;
#include< string.h >
struct college
{
int prof.id;
char pname[20];
char dept[20];
} p[10];
int main()
{
int i;
for (i=0; i<10; i++)
{
cout << "Enter professor.id'' << endl;
cin >> p[i].prof_d;
cout << "Enter proferssor name'' << endl:
cin >> p[i].pname;
cout << "Enter department'' << endl;
cin >> p[i].dept;
}
for(i=0;i < 10; i++) 
{
int flag= 1;
if(p[i].dept== "COMP.SCI"&& p[i].pname='A')
cout << p[i].prof id << endl;
cout << p[i].pname << endl;
cout << p[i].dept << endl;
}
if(flag==0)
cout << "The given details not found" << endly
return 0;
}

A function that calls itself is known as recursive function. And, this technique is known as recursion.
#include
using namespace std;
int factorial(int);//Function prototype//
int main ()
{
int no;
cout <<"\nEnter a number to find its factorial;";
cin>>no;
cout <<"\nFactorial of Number" < return 0;
}
int factorial(int m)
{
if (m>1)
{
return m*factorial(m-1);
}
else
{
return 1;
}
}
Output:
Enter a number to find its factorial: 5
Factorial of Number 5 = 120

1920₁₀ = ?₂

= 11110000000₂ 
= 11110000000₂ = ?₈
= \(\overline { \underset { \overset { \downarrow }{ 3 } }{ 11 } } \)  \(\overline { \underset { \overset { \downarrow }{ 6 } }{ 110 } } \) \(\overline { \underset { \overset { \downarrow }{ 0 } }{ 000 } } \) \(\overline { \underset { \overset { \downarrow }{ 0 } }{ 000} } \)
= 3600₈
= 11110000000₂ = ?₁₆
= \(\overline { \underset { \overset { \downarrow }{ 7 } }{ 111 } } \) \(\overline { \underset { \overset { \downarrow }{ 8 } }{ 1000 } } \) \(\overline { \underset { \overset { \downarrow }{ 0 } }{ 0000} } \)
= 78016
= 1920₁₀ = 11110000000₂ = 3600₈ = 780₁₆

There are several methods of transferring files to or from a removable disk.
(i) Copy and Paste
(ii) Drag and Drop
(iii) Send To
(iv) Copy and Paste using keyboard shortcuts
METHOD 1:
Plug the USB flash drive directly into an available USB port.

(i) Click Start ⟶ Computer.
(ii) Double-click on the Removable Disk associated with the USB flash drive.


(i) Navigate to the folders in your computer containing files you want to transfer Right click on the file you want to copy, then select Copy.
(ii) Return to Removable Disk window, right click within the window, then select Paste.

METHOD 2:
Drag and Drop
(i) Plug the USB flash drive directly into an available USB port.
(ii) Allow the computer to recognize the drive, then click Start ⟶ Computer.
(iii) Navigate to 'the folders in your computer containing files you want to transfer.
(iv) Click and drag the files you want to the Removable Disk.
(v) Release the mouse.
METHOD 3:
Send To (Windows)
(i) Plug the USB flash drive directly into an available USB port.

(ii) Navigate to the folders in your computer containing files you want to transfer.
(iii) Right-click on the file you want to transfer to your removable disk.
(iv) Click Send To and select the Removable Disk associated with the USB flash drive.
METHOD 4:
Copy and Paste using keyboard shortcuts (Windows)
(i) Plug the USB flash drive directly into an available USB port.
(ii) Click on your desired file to select it.
(iii) On your keyboard, hold down the Ctrl key and press C.
(iv) Navigate to the desired folder destination.
(v) Hold down the Ctrl key and press V.

(i) f=1 i=1 f = f * i i = i+1
f = 1 x 1 = 1 i = 2
(ii) f = 1 x 2 i = 3 = 2
(iii) f = 2 × 3 i = 4 = 6
(iv) f = 6 x 4 i = 5 (loop terminates) = 24

S.No Versions Logo Year Prominent feature 1. Windows 1.x 1985 1. Introduction of GUI in 16 - bit. processor
2. Mouse was introduced as an input device 2. Windows 2.x 1987 1. Supports to minimize or maximize windows.
2. Control panel feature was introduced with
various system settings and customizing options. 3. Windows 3.x 1992 1. Introduced the concept of multitasking.
2. Supported 256 colors which brought a more
modern, colorful look to the interface. 4. Windows 95 1995 1. Introduced Start button, the taskbar, Windows Explorer and Start menu.
2. Introduced 32 - bit processor and focused more on multitasking. 5. Windows 98 1998 1. Integration of the Web browser (Internet Explorer) with the Operating System.
2. DOS gaming began to disappear as Windows-based games improved.
3. Plug and play feature was introduced. 6. Windows NT   Designed to act as servers in network. 7. Windows Me 2000 It introduced automated system diagnostics and recovery tools. 8. Windows 2000 2000 1. Served as an Operating System for business
desktop and laptop systems.
2. Four versions of Windows 2000 were released: Professional (for business)
3. desktop and laptop systems), Server (both a
Web server and an office server),
4. Advanced Server (for line-of-business 
applications) and Data Centre Server (for high traffic computer networks). 9. Windows XP 2001 1. Introduced 64-bit Processor.
2. Improved Windows appearance with themes and offered a stable version 10. Windows Vista 2006 Updated the look and feel of Windows 11. Windows 7 2009 Booting time was improved, introduced new user interfaces like Aero Peek, pinning programs to the taskbar, handwriting recognition etc, and Internet Explorer 8. 12. Windows 8 2012 1. Windows 8 was faster than previous versions of Windows.
2. Start button was removed
3. Windows 8 takes better advantage of multicore processing, solid-state drives (SSD), touch screens, and other alternate input methods.
4. Served as a common platform for mobile and computer. 13. Windows 10 2015 1. Start Button was added again.
2. Multiple desktops.
3. Central Notification Center for App notification and quick actions.
4. Cortana voice-activated personal assistant.

1101011₂ - 111010₂
1101011
+111010
_______
0110001
_______
1101011₂ - 111010₂  = 0110001₂

1. hypotenuse (a, b)
2. -- inputs: a, b are real numbers, a > 0, b > 0
3 -- outputs: c²=a² + b² where c is real number, c > 0

Computers size was drastically reduced. S.No	Generation	Period	Main Component used	Merits/ Demerits
1	First Generation	1942-1955		Big in size Consumed more power Malfunction due to overheating Machine Language was used Eg : ENIAC, EDVAC, UNIVAC
First Generation Computer - ENIAC, EDVAC, UNIVAC 1 ENIAC weighed about 27 tons, size 8 feet x 100 feet x 3 feet, and consumed around 150 watts of power
2	Second Generation	1955-1964		Smaller compared to First Generation Generated Less Heat Consumed less power compared to first-generation Punched cards were used. The first operating system was developed Batch Processing and Multiprogramming Operating System Machine language, as well as Assembly language, was used.
Second Generation Computers IBM 1404, IBM 1620, UNIVAC 1108
3	Third Generation	1964-1975		Computers were smaller, faster, and more reliable Consumed less power. High-Level Languages were used.
Third Generation Computers -IBM ·360 series, Honeywell 6000 series
4	Fourth Generation	1975-1980		Smaller and Faster Microcomputer series such as IBM and APPLE was developed Portable Computers were introduced.
5	Fifth Generation	1980-till date		Parallel, Processing Superconductors Computers size was drastically reduced. Can recognize Images and Graphics Introduction of Artificial Intelligence and Expert Systems Able to solve highly complex problems including decision making and logical reasoning.
6	Sixth Generation	In future		Parallel and Distributed computing Computers have become smarter faster and smaller Development of robotics Natural Language Processing Development of Voice Recognition Software.

(a) Clock speed-Each microprocessor has an internal clock that regulates the speed at which it executes instructions. The speed at which the microprocessor executes instructions is called clock speed. It is measured in MHz vi in GHz.
(b) Instructions set - The set of machine level instructions that a microprocessor is designed to execute is called as an instruction set. This carries 4 types of operations. They are
1. Data transfer
2. Arithmetic operations
3. Logical Operations
4. Control flow
5. Input/output
(c) Word size - The number of bits that can be processed by a processor in a single instruction is called as its word size. It determines the amount of RAM that can be accessed at one time and the total number of pins on the microprocessor. Total number of input and output pins in turn determines the architecture of the microprocessor.