Introduction to C++

1. Basic Program

hello.cpp

#include <iostream>
 
using namespace std;
 
int main() {
    cout << "Hello World";
    return 0;
}

2. Explanation of Program

#include iostream: Used for input and output operations.
using namespace std;: Allows use of standard library objects without writing std::.
cout: Used to display output.
int main(): Main function where program execution begins.
cout: Used to display output.
return 0;: Indicates successful execution

3. Applications of C++

Field	Usage
Game Development	Game engines
Operating Systems	Windows, Linux components
Web Browsers	Browser engines
Embedded Systems	Microcontrollers
Databases	MySQL
Competitive Programming	Fast execution

4. Variables & Data Types

4.1 Variables

Variables are named memory locations that hold values.

4.2 Data Types

Data types define the kind of data a variable can hold.

Data Type	Size	Example
int	4 Bytes	10
float	4 Bytes	3.14
double	8 Bytes	10.5678
char	1 Byte	'A'
bool	1 Byte	true
short	2 Bytes	120
long	4 or 8 Bytes	123456
long long	8 Bytes	9876543210
string	Depends on Length	"Hello"

datatypes.cpp

#include <iostream>
using namespace std;
 
int main()
{
 
    int num = 534;
    cout << num << endl;
 
    long int lnum = 34;
    cout << lnum << endl;
 
    float x = 35.99;
    cout << x << endl;
 
    double a = 93.98;
    cout << a << endl;
 
    char c = 'A';
    cout << c << endl;
 
    bool isTrue = false;
    cout <<  isTrue << endl;
 
    string str = "Hello World!";
    cout << str << endl;
 
    return 0;
}

5. Type Casting

Type casting is the process of converting one data type to another.

5.1 Implicit Type Casting

Automatic conversion of lower precision to higher precision data type.
No risk of data loss.

Example:

implicit-cast.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int a = 10;
    double b = a;
    cout << b << endl;
 
    return 0;
}

5.2 Explicit Type Casting

Manual conversion of higher precision to lower precision data type.
Risk of data loss.

Example:

explicit-cast.cpp

#include <iostream>
using namespace std;
 
int main()
{
    double a = 10.5;
 
    int b = (int)a;
    // int b = static_cast<int>(a);
 
    cout << b << endl;
 
    return 0;
}

6. Conditional Statement

Conditional statements are used to make decisions on the basis of a condition.

Write a program to check if a number is even or odd using if-else statement.

even-odd.cpp

#include <iostream> 
using namespace std;
 
int main() {
    int n;
    cout << "Enter a number: ";
 
    cin >> n; //? read the user input
    
    if (n % 2 == 0) {
        cout << n << " is even no." << endl;
    } else {
        cout << n << " is odd no." << endl;
    }
 
    return 0;
}

7. Loop Statement

Loop statements are used to repeat a block of code until a condition condition is met.

for loop
while loop
do-while loop

7.1 for Loop

Used to repeat a block of code a fixed number of times.
Syntax: for (initialization; condition; increment/decrement)

for-loop.cpp

#include <iostream>
using namespace std;
 
int main()
{
    for (int i = 0; i < 5; i++)
    {
        cout << i << endl;
    }
 
    return 0;
}

7.2 while Loop

Used to repeat a block of code until a condition is met.
Syntax: while (condition)

while-loop.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int i = 0;
    while (i < 5)
    {
        cout << i << endl;
        i++;
    }
 
    return 0;
}

7.3 do-while Loop

Used to repeat a block of code at least once.
Syntax: do while (condition);

do-while-loop.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int i = 0;
    do
    {
        cout << i << endl;
        i++;
    } while (i < 5);
 
    return 0;
}

8. Operators

Operators are symbols that are used to perform operations on variables and values.

8.1 Arithmetic Operators

+ (Addition)
- (Subtraction)
* (Multiplication)
/ (Division)
% (Modulus)

8.2 Assignment Operators

= (Assignment)
+= (Addition Assignment)
-= (Subtraction Assignment)
*= (Multiplication Assignment)
/= (Division Assignment)
%= (Modulus Assignment)

8.3 Comparison Operators

== (Equal)
!= (Not Equal)
== (Identity)
!== (Not Identity)
< (Less Than)
> (Greater Than)
<= (Less Than or Equal)
>= (Greater Than or Equal)

8.4 Logical Operators

&& (AND)
|| (OR)
! (NOT)

8.5 Bitwise Operators

& (AND)
| (OR)
~ (NOT)
^ (XOR)
<< (Left Shift)
>> (Right Shift)

8.6 Pre & Post Increment/Decrement Operators

++ (Pre-Increment): first increment then use the value
-- (Pre-Decrement): first decrement then use the value
++ (Post-Increment): first use the value then increment
-- (Post-Decrement): first use the value then decrement

Example:

operators.cpp

#include <iostream>
 
using namespace std;
 
int main() {
    //* Arithmetic Operators
    int a = 5, b = 3;
    cout << "a + b = " << a + b << endl;
    cout << "a - b = " << a - b << endl;
    cout << "a * b = " << a * b << endl;
    cout << "a / b = " << a / b << endl;
    cout << "a % b = " << a % b << endl;
 
    //* Relational Operators
    cout << "a == b = " << (a == b) << endl;
    cout << "a != b = " << (a != b) << endl;
    cout << "a > b = " << (a > b) << endl;
    cout << "a < b = " << (a < b) << endl;
    cout << "a >= b = " << (a >= b) << endl;
    cout << "a <= b = " << (a <= b) << endl;
 
    //* Logical Operators
    cout << "a && b = " << (a && b) << endl;
    cout << "a || b = " << (a || b) << endl;
 
    //* Bitwise Operators
    cout << "a & b = " << (a & b) << endl;
    cout << "a | b = " << (a | b) << endl;
    cout << "~a = " << (~a) << endl;
    cout << "a << b = " << (a << b) << endl;
    cout << "a >> b = " << (a >> b) << endl;
 
    //* Assignment Operators
    cout << "a += b = " << (a += b) << endl;
    cout << "a -= b = " << (a -= b) << endl;
    cout << "a *= b = " << (a *= b) << endl;
    cout << "a /= b = " << (a /= b) << endl;
    cout << "a %= b = " << (a %= b) << endl;
 
    return 0;
}

9. Switch Statement, Break & Continue

9.1 Switch Statement

Used to execute one of many blocks of code based on the value of a variable.
Syntax: switch (expression) { case label: code; break; default: code; break; }

switch.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int a = 3;
    switch (a)
    {
    case 1:
        cout << "a is 1" << endl;
        break;
    case 2:
        cout << "a is 2" << endl;
        break;
    case 3:
        cout << "a is 3" << endl;
        break;
    default:
        cout << "a is not 1, 2, or 3" << endl;
        break;
    }
    return 0;
}

9.2 Break Statement

Used to exit a loop or switch statement.
Syntax: break;

9.3 Continue Statement

Used to skip the current iteration of a loop and continue with the next iteration.
Syntax: continue;

10. Some Basic Programs

10.1 Multiplication Table of n

Write a program to print the multiplication table of n.

Code:

multiplication.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int n;
    cout << "Enter value of n: ";
    cin >> n;
 
    for (int i = 1; i <= 10; i++)
    {
        cout << n << " * " << i << " = " << n * i << endl;
    }
 
    return 0;
}

Output:

Enter value of n: 12
12 * 1 = 12
12 * 2 = 24
12 * 3 = 36
12 * 4 = 48
12 * 5 = 60
12 * 6 = 72
12 * 7 = 84
12 * 8 = 96
12 * 9 = 108
12 * 10 = 120

10.2 Power of a Number

Write a program to calculate the power of a number.

Code:

power.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int base, power;
    cout << "Enter a base: ";
    cin >> base;
    cout << "Enter a power: ";
    cin >> power;
 
    int res = base;
 
    for (int i = 1; i < power; i++)
    {
        res = res * base;
    }
    cout << base << "^" << power << " = " << res << endl;
 
    return 0;
}

Output:

Enter a base: 3
Enter a power: 3
3^3 = 27

10.3 Check if a Number is Prime or Not

Write a program to check if a number is prime or not.

Code:

prime.cpp

#include <iostream>
using namespace std;
 
int main()
{
    int n;
    cout << "Enter a no: ";
    cin >> n;
    bool isPrime = false;
 
    if (n < 2)
    {
        isPrime = false;
    }
    else if (n == 2)
    {
        isPrime = true;
    }
    else if (n % 2 == 0)
    {
        isPrime = false;
    }
    else
    {
        for (int i = 3; i * i <= n; i+=2)
        {
            if (n % i == 0)
            {
                isPrime = false;
                break;
            }
        }
        isPrime = true;
    }
 
    if (isPrime)
    {
        cout << n << " is a prime no." << endl;
    }
    else
    {
        cout << n << " is not a prime no." << endl;
    }
 
    return 0;
}

Output:

Enter a no: 12 12 is not a prime no.

10.4 Fibonacci Series

Write a program to print the first n Fibonacci numbers.

n = 11: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55,

Code:

fibonacci.cpp

#include <iostream>
 
using namespace std;
 
int main()
{
    int n;
 
    cout << "Enter a no: ";
    cin >> n;
 
    int a = 0, b = 1, c = 0;
 
    for (int i = 1; i <= n; i++)
    {
        cout << c << ", ";
        a = b;
        b = c;
        c = a + b;
    }
    
    return 0;
}

Output:

Enter a no: 12 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89,