C++ Basics and Programs

C++ is programming language where you can develop software’s. its runs on different platforms
Windows, Mac, different version of Linux.
It is use to develop

1. Application Software Development
2. Programming languages development
3. Computation Programming
4. Games Development
5. Embedded Systems

Object-Oriented Programming
C++ Supports OOP concepts with its Four Pillars.
More Detail….

1. Encapsulation
2. Data hiding
3. Inheritance
4. Polymorphism

C++ does not allow punctuation characters such as @, $, and % within identifiers. C++ is a case-sensitive programming language.

• <iostream> is a header, which contain information that is either necessary or useful to your program. the header <iostream> is needed for programs.
• The line using namespace std; tells the compiler to use the std namespace.
• main() where program execution begins.
• // is a single-line comment available in C++. Single-line comments begin with // and stop at the end of the line.
• The line int main() is the main function where program execution begins.
• cout << “Hello World”; shows the message “Hello World” to be displayed on the screen.
• return 0; 
• terminates main( ) function. Because int method requires value to terminate the function.

Simple code to print Hello World.

#include <iostream>
 using namespace std;
 // main() is where program execution begins. 
int main() 
{    cout << "Hello World"; // prints Hello World    
return 0; 
}

• <iostream> is a header, which contain information that is either necessary or useful to your program. the header <iostream> is needed for programs.
• The line using namespace std; tells the compiler to use the std namespace.
• main() where program execution begins.
• // is a single-line comment available in C++. Single-line comments begin with // and stop at the end of the line.
• The line int main() is the main function where program execution begins.
• cout << “Hello World”; shows the message “Hello World” to be displayed on the screen.
• return 0; 
• terminates main( ) function. Because int method requires value to terminate the function

How to Compile and Execute C++ Program.

• Open a text editor and add the code as above.
• Save the file as: result.cpp
• Open a command prompt and go to the directory where you saved the file.
• Type ‘g++ result.cpp’ and press enter to compile your code. command prompt will take you to the next line and would generate a.out executable file if there is no error.
• Now, type ‘a.out’ to run your program.
• You will be able to see ‘ Hello World ‘ printed on the window.

Semicolons and Blocks in C++

Samicolons are end operators which terminates the function and shows individually statements

x = y; 
y = y + 1; 
add(x, y);

A block is a set of logically connected statements that are surrounded by opening and closing braces. For example

{    
cout << "Hello World"; 
// prints Hello World    
return 0; 
}

Primitive Built-in Types

Type	Keyword
Boolean	bool
Character	char
Integer	int
Floating point	float
Double floating point	double
Valueless	void
Wide character	wchar_t

Type	Typical Bit Width	Typical Range
char	1byte	-127 to 127 or 0 to 255
unsigned char	1byte	0 to 255
signed char	1byte	-127 to 127
int	4bytes	-2147483648 to 2147483647
unsigned int	4bytes	0 to 4294967295
signed int	4bytes	-2147483648 to 2147483647
short int	2bytes	-32768 to 32767
unsigned short int	2bytes	0 to 65,535
signed short int	2bytes	-32768 to 32767
long int	8bytes	-2,147,483,648 to 2,147,483,647
signed long int	8bytes	same as long int
unsigned long int	8bytes	0 to 4,294,967,295
long long int	8bytes	-(2^63) to (2^63)-1
unsigned long long int	8bytes	0 to 18,446,744,073,709,551,615
float	4bytes
double	8bytes
long double	12bytes
wchar_t	2 or 4 bytes	1 wide character

Example
#include <iostream>
 using namespace std;
 int main()
 {    
cout << "Size of char : " << sizeof(char) << endl;
cout << "Size of int : " << sizeof(int) << endl;    
cout << "Size of short int : " << sizeof(short int) << endl;    
cout << "Size of long int : " << sizeof(long int) << endl;    
cout << "Size of float : " << sizeof(float) << endl;    
cout << "Size of double : " << sizeof(double) << endl;    
cout << "Size of wchar_t : " << sizeof(wchar_t) << endl;        
return 0; 
}

Print Number Entered by User

#include <iostream>
using namespace std;

int main() {    
    int number;

    cout << "Enter an integer: ";
    cin >> number;

    cout << "You entered " << number;    
    return 0;
}

Output:
Enter an integer: 23
You entered 23

print triangles using *, numbers and characters

#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "Enter number of rows: ";
    cin >> rows;

    for(int i = 1; i <= rows; ++i)
    {
        for(int j = 1; j <= i; ++j)
        {
            cout << "* ";
        }
        cout << "\n";
    }
    return 0;
}
Output
*
* *
* * *
* * * *
* * * * *
---------------------------------------
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "Enter number of rows: ";
    cin >> rows;

    for(int i = 1; i <= rows; ++i)
    {
        for(int j = 1; j <= i; ++j)
        {
            cout << j << " ";
        }
        cout << "\n";
    }
    return 0;
}

Output
1
1 2
1 2 3
1 2 3 4
1 2 3 4 5
------------------------------
#include <iostream>
using namespace std;

int main()
{
    char input, alphabet = 'A';

    cout << "Enter the uppercase character you want to print in the last row: ";
    cin >> input;

    for(int i = 1; i <= (input-'A'+1); ++i)
    {
        for(int j = 1; j <= i; ++j)
        {
            cout << alphabet << " ";
        }
        ++alphabet;

        cout << endl;
    }
    return 0;
}

Output
A
B B
C C C
D D D D
E E E E E
----------------------------------------
#include <iostream>
using namespace std;

int main()
{
    int rows;

    cout << "Enter number of rows: ";
    cin >> rows;

    for(int i = rows; i >= 1; --i)
    {
        for(int j = 1; j <= i; ++j)
        {
            cout << "* ";
        }
        cout << endl;
    }
    
    return 0;
}

Output
* * * * *
* * * *
* * * 
* *
*
-------------------------------------------
#include <iostream>
using namespace std;

int main()
{
    int space, rows;

    cout <<"Enter number of rows: ";
    cin >> rows;

    for(int i = 1, k = 0; i <= rows; ++i, k = 0)
    {
        for(space = 1; space <= rows-i; ++space)
        {
            cout <<"  ";
        }

        while(k != 2*i-1)
        {
            cout << "* ";
            ++k;
        }
        cout << endl;
    }    
    return 0;
}

Output
        *
      * * *
    * * * * *
  * * * * * * *
* * * * * * * * *

Length of String Object

#include <iostream>
using namespace std;

int main() {
    string str = "C++ Programming";

    // you can also use str.length()
    cout << "String Length = " << str.size();

    return 0;
}

Output
String Length = 15

Concatenate String Objects

#include <iostream>
using namespace std;

int main()
{
    string s1, s2, result;

    cout << "Enter string s1: ";
    getline (cin, s1);

    cout << "Enter string s2: ";
    getline (cin, s2);

    result = s1 + s2;

    cout << "Resultant String = "<< result;

    return 0;
}

Output
Enter string s1: C++ Programming
Enter string s2:  is awesome.
Resultant String = C++ Programming is awesome.

Copy String Object

#include <iostream>
using namespace std;

int main()
{
    string s1, s2;

    cout << "Enter string s1: ";
    getline (cin, s1);

    s2 = s1;

    cout << "s1 = "<< s1 << endl;
    cout << "s2 = "<< s2;

    return 0;
}

output
Enter string s1: C++ Strings
s1 = C++ Strings
s2 = C++ Strings

Simple Calculator using switch statement

# include <iostream>
using namespace std;

int main() {
    char op;
    float num1, num2;

    cout << "Enter operator: +, -, *, /: ";
    cin >> op;

    cout << "Enter two operands: ";
    cin >> num1 >> num2;

    switch(op) {
        case '+':
            cout << num1 << " + " << num2 << " = " << num1 + num2;
            break;

        case '-':
            cout << num1 << " - " << num2 << " = " << num1 - num2;
            break;

        case '*':
            cout << num1 << " * " << num2 << " = " << num1 * num2;
            break;

        case '/':
            cout << num1 << " / " << num2 << " = " << num1 / num2;
            break;

        default:
            // If the operator is other than +, -, * or /, error message is shown
            cout << "Error! operator is not correct";
            break;
    }

    return 0;
}

Output
Enter operator either + or - or * or divide : -
Enter two operands: 3.4 8.4
3.4 - 8.4 = -5.0

Program to Add Two Integers

#include <iostream>
using namespace std;

int main()
{
    int firstNumber, secondNumber, sumOfTwoNumbers;
    
    cout << "Enter two integers: ";
    cin >> firstNumber >> secondNumber;

    // sum of two numbers in stored in variable sumOfTwoNumbers
    sumOfTwoNumbers = firstNumber + secondNumber;

    // Prints sum 
    cout << firstNumber << " + " <<  secondNumber << " = " << sumOfTwoNumbers;

Output:
Enter two integers: 4
5
4 + 5 = 9

Quotient and remainder

#include <iostream>
using namespace std;

int main()
{    
    int divisor, dividend, quotient, remainder;

    cout << "Enter dividend: ";
    cin >> dividend;

    cout << "Enter divisor: ";
    cin >> divisor;

    quotient = dividend / divisor;
    remainder = dividend % divisor;

    cout << "Quotient = " << quotient << endl;
    cout << "Remainder = " << remainder;

    return 0;
}
Output:
Enter dividend: 13
Enter divisor: 4
Quotient = 3
Remainder = 1

Find Size of a Variable

#include <iostream>
using namespace std;

int main() 
{    
    cout << "Size of char: " << sizeof(char) << " byte" << endl;
    cout << "Size of int: " << sizeof(int) << " bytes" << endl;
    cout << "Size of float: " << sizeof(float) << " bytes" << endl;
    cout << "Size of double: " << sizeof(double) << " bytes" << endl;

    return 0;
}

Output:
Size of char: 1 byte
Size of int: 4 bytes
Size of float: 4 bytes
Size of double: 8 bytes

Swap Numbers (Using Temporary Variable)

#include <iostream>
using namespace std;

int main()
{
    int a = 5, b = 10, temp;

    cout << "Before swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    temp = a;
    a = b;
    b = temp;

    cout << "\nAfter swapping." << endl;
    cout << "a = " << a << ", b = " << b << endl;

    return 0;
}

Output:
Before swapping.
a = 5, b = 10

After swapping.
a = 10, b = 5

Print ASCII Value in C++

#include <iostream>
using namespace std;

int main() {
 char c;
 cout << "Enter a character: ";
 cin >> c;
 cout << "ASCII Value of " << c << " is " << int(c);
 return 0;
}

Output
Enter a character: p
ASCII Value of p is 112

Program to Multiply Two Numbers:

#include <iostream>
using namespace std;

int main()
{
    double firstNumber, secondNumber, productOfTwoNumbers;
    cout << "Enter two numbers: ";

    // Stores two floating point numbers in variable firstNumber and secondNumber respectively
    cin >> firstNumber >> secondNumber;
 
    // Performs multiplication and stores the result in variable productOfTwoNumbers
    productOfTwoNumbers = firstNumber * secondNumber;  

    cout << "Product = " << productOfTwoNumbers;    
    
    return 0;
}

Output:
Enter two numbers: 3.4
5.5
Product = 18.7

Check Whether Number is Even or Odd

#include <iostream>
using namespace std;

int main()
{
    int n;

    cout << "Enter an integer: ";
    cin >> n;

    if ( n % 2 == 0)
        cout << n << " is even.";
    else
        cout << n << " is odd.";

    return 0;

Output:
Enter an integer: 23
23 is odd.

Check Whether Number is Even or Odd using ternary

#include <iostream>
using namespace std;

int main()
{
    int n;

    cout << "Enter an integer: ";
    cin >> n;
    
    (n % 2 == 0) ? cout << n << " is even." :  cout << n << " is odd.";
    
    return 0;
}

Check Whether a character is Vowel or Consonant.

#include <iostream>
using namespace std;

int main() {
    char c;
    bool isLowercaseVowel, isUppercaseVowel;

    cout << "Enter an alphabet: ";
    cin >> c;

    // evaluates to 1 (true) if c is a lowercase vowel
    isLowercaseVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');

    // evaluates to 1 (true) if c is an uppercase vowel
    isUppercaseVowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');

    // show error message if c is not an alphabet
    if (!isalpha(c))
      printf("Error! Non-alphabetic character.");
    else if (isLowercaseVowel || isUppercaseVowel)
        cout << c << " is a vowel.";
    else
        cout << c << " is a consonant.";

    return 0;
}

Output
Enter an alphabet: u
u is a vowel.

Find Largest Number Using if Statement

#include <iostream>
using namespace std;

int main() {    
    float n1, n2, n3;

    cout << "Enter three numbers: ";
    cin >> n1 >> n2 >> n3;

    if(n1 >= n2 && n1 >= n3)
        cout << "Largest number: " << n1;

    if(n2 >= n1 && n2 >= n3)
        cout << "Largest number: " << n2;
    
    if(n3 >= n1 && n3 >= n2)
        cout << "Largest number: " << n3;
  
    return 0;
}

Output
Enter three numbers: 2.3
8.3
-4.2
Largest number: 8.3

Find Largest Number Using if…else Statement

#include <iostream>
using namespace std;

int main() {
    float n1, n2, n3;

    cout << "Enter three numbers: ";
    cin >> n1 >> n2 >> n3;

    if((n1 >= n2) && (n1 >= n3))
        cout << "Largest number: " << n1;
    else if ((n2 >= n1) && (n2 >= n3))
        cout << "Largest number: " << n2;
    else
        cout << "Largest number: " << n3;
    
    return 0;
}

Output
Enter three numbers: 2.3
8.3
-4.2
Largest number: 8.3

Find Largest Number Using Nested if…else statement

#include <iostream>
using namespace std;

int main() {
    float n1, n2, n3;

    cout << "Enter three numbers: ";
    cin >> n1 >> n2 >> n3;

    if (n1 >= n2) {
        if (n1 >= n3)
            cout << "Largest number: " << n1;
        else
            cout << "Largest number: " << n3;
    }
    else {
        if (n2 >= n3)
            cout << "Largest number: " << n2;
        else
            cout << "Largest number: " << n3;
    }

    return 0;
}

Output
Enter three numbers: 2.3
8.3
-4.2
Largest number: 8.3

Sum of Natural Numbers using loop

#include <iostream>
using namespace std;

int main() {
    int n, sum = 0;

    cout << "Enter a positive integer: ";
    cin >> n;

    for (int i = 1; i <= n; ++i) {
        sum += i;
    }

    cout << "Sum = " << sum;
    return 0;
}

output
Enter a positive integer: 50
Sum = 1275

Check if a year is leap year or not

#include <iostream>
using namespace std;

int main() {
    int year;

    cout << "Enter a year: ";
    cin >> year;

    if (year % 4 == 0) {
        if (year % 100 == 0) {
            if (year % 400 == 0)
                cout << year << " is a leap year.";
            else
                cout << year << " is not a leap year.";
        }
        else
            cout << year << " is a leap year.";
    }
    else
        cout << year << " is not a leap year.";

    return 0;
}

Output
Enter a year: 2014
2014 is not a leap year.

Find Factorial of a given number

#include <iostream>
using namespace std;

int main() {
    int n;
    long double factorial = 1.0;

    cout << "Enter a positive integer: ";
    cin >> n;

    if (n < 0)
        cout << "Error! Factorial of a negative number doesn't exist.";
    else {
        for(int i = 1; i <= n; ++i) {
            factorial *= i;
        }
        cout << "Factorial of " << n << " = " << factorial;    
    }

    return 0;
}

Output
Enter a positive integer: 12
Factorial of 12 = 479001600

Display Multiplication table up to 10

#include <iostream>
using namespace std;

int main()
{
    int n;

    cout << "Enter a positive integer: ";
    cin >> n;

    for (int i = 1; i <= 10; ++i) {
        cout << n << " * " << i << " = " << n * i << endl;
    }
    
    return 0;
}

Output:
Enter an integer: 5
5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

Display multiplication table up to a given range

#include <iostream>
using namespace std;

int main()
{
    int n, range;

    cout << "Enter an integer: ";
    cin >> n;

    cout << "Enter range: ";
    cin >> range;
    
    for (int i = 1; i <= range; ++i) {
        cout << n << " * " << i << " = " << n * i << endl;
    }
    
    return 0;
}

Output
Enter an integer: 8
Enter range: 12
8 * 1 = 8
8 * 2 = 16
8 * 3 = 24
8 * 4 = 32
8 * 5 = 40
8 * 6 = 48
8 * 7 = 56
8 * 8 = 64
8 * 9 = 72
8 * 10 = 80
8 * 11 = 88
8 * 12 = 96

Fibonacci Series up to n number of terms

#include <iostream>
using namespace std;

int main() {
    int n, t1 = 0, t2 = 1, nextTerm = 0;

    cout << "Enter the number of terms: ";
    cin >> n;

    cout << "Fibonacci Series: ";

    for (int i = 1; i <= n; ++i) {
        // Prints the first two terms.
        if(i == 1) {
            cout << t1 << ", ";
            continue;
        }
        if(i == 2) {
            cout << t2 << ", ";
            continue;
        }
        nextTerm = t1 + t2;
        t1 = t2;
        t2 = nextTerm;
        
        cout << nextTerm << ", ";
    }
    return 0;
}

Output
Enter the number of terms: 10
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 

Program to Generate Fibonacci Sequence Up to a Certain Number

#include <iostream>
using namespace std;

int main() {
    int t1 = 0, t2 = 1, nextTerm = 0, n;

    cout << "Enter a positive number: ";
    cin >> n;

    // displays the first two terms which is always 0 and 1
    cout << "Fibonacci Series: " << t1 << ", " << t2 << ", ";

    nextTerm = t1 + t2;

    while(nextTerm <= n) {
        cout << nextTerm << ", ";
        t1 = t2;
        t2 = nextTerm;
        nextTerm = t1 + t2;
    }
    return 0;
}
Output
Enter a positive integer: 100
Fibonacci Series: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 

Find GCD using while loop

#include <iostream>
using namespace std;

int main()
{
    int n1, n2;

    cout << "Enter two numbers: ";
    cin >> n1 >> n2;
    
    while(n1 != n2)
    {
        if(n1 > n2)
            n1 -= n2;
        else
            n2 -= n1;
    }

    cout << "HCF = " << n1;
    return 0;
}

Output
Enter two numbers: 78
52
HCF = 26

Find HCF/GCD using for loop

#include <iostream>
using namespace std;

int main() {
    int n1, n2, hcf;
    cout << "Enter two numbers: ";
    cin >> n1 >> n2;

    // Swapping variables n1 and n2 if n2 is greater than n1.
    if ( n2 > n1) {   
        int temp = n2;
        n2 = n1;
        n1 = temp;
    }
    
    for (int i = 1; i <=  n2; ++i) {
        if (n1 % i == 0 && n2 % i ==0) {
            hcf = i;
        }
    }

    cout << "HCF = " << hcf;
    return 0;
}

Find LCM

#include <iostream>
using namespace std;

int main()
{
    int n1, n2, max;

    cout << "Enter two numbers: ";
    cin >> n1 >> n2;
    
    // maximum value between n1 and n2 is stored in max
    max = (n1 > n2) ? n1 : n2;

    do
    {
        if (max % n1 == 0 && max % n2 == 0)
        {
            cout << "LCM = " << max;
            break;
        }
        else
            ++max;
    } while (true);
    
    return 0;
}

output
Enter two numbers: 12
18
LCM = 36

Find LCM using HCF

#include <iostream>
using namespace std;

int main()
{
    int n1, n2, hcf, temp, lcm;

    cout << "Enter two numbers: ";
    cin >> n1 >> n2;

    hcf = n1;
    temp = n2;
    
    while(hcf != temp)
    {
        if(hcf > temp)
            hcf -= temp;
        else
            temp -= hcf;
    }

    lcm = (n1 * n2) / hcf;

    cout << "LCM = " << lcm;
    return 0;
}

Reverse an Integer

#include <iostream>
using namespace std;

int main() {
    int n, reversedNumber = 0, remainder;

    cout << "Enter an integer: ";
    cin >> n;

    while(n != 0) {
        remainder = n%10;
        reversedNumber = reversedNumber*10 + remainder;
        n /= 10;
    }

    cout << "Reversed Number = " << reversedNumber;

    return 0;
}

Output
Enter an integer: 12345
Reversed number = 54321

Compute Power Manually

#include <iostream>
using namespace std;

int main() 
{
    int exponent;
    float base, result = 1;

    cout << "Enter base and exponent respectively:  ";
    cin >> base >> exponent;

    cout << base << "^" << exponent << " = ";

    while (exponent != 0) {
        result *= base;
        --exponent;
    }

    cout << result;
    
    return 0;
}

Output
Enter base and exponent respectively:  3.4
5
3.4^5 = 454.354

Compute power using pow() Function

#include <iostream>
#include <cmath>

using namespace std;

int main() 
{
    float base, exponent, result;

    cout << "Enter base and exponent respectively:  ";
    cin >> base >> exponent;

    result = pow(base, exponent);

    cout << base << "^" << exponent << " = " << result;
    
    return 0;
}

Output
Enter base and exponent respectively:  2.3
4.5
2.3^4.5 = 42.44

Check Palindrome Number

#include <iostream>
using namespace std;

int main()
{
     int n, num, digit, rev = 0;

     cout << "Enter a positive number: ";
     cin >> num;

     n = num;

     do
     {
         digit = num % 10;
         rev = (rev * 10) + digit;
         num = num / 10;
     } while (num != 0);

     cout << " The reverse of the number is: " << rev << endl;

     if (n == rev)
         cout << " The number is a palindrome.";
     else
         cout << " The number is not a palindrome.";

    return 0;
}

Output
Enter a positive number: 12321
The reverse of the number is: 12321
The number is a palindrome.
OR
Enter a positive number: 12331
The reverse of the number is: 13321
The number is not a palindrome.

Check Prime Number

#include <iostream>
using namespace std;

int main() {
    int i, n;
    bool isPrime = true;

    cout << "Enter a positive integer: ";
    cin >> n;

    // 0 and 1 are not prime numbers
    if (n == 0 || n == 1) {
        isPrime = false;
    }
    else {
        for (i = 2; i <= n / 2; ++i) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
    }
    if (isPrime)
        cout << n << " is a prime number";
    else
        cout << n << " is not a prime number";

    return 0;
}

Output
Enter a positive integer: 29
29 is a prime number.

Display Prime Numbers Between two Intervals

#include <iostream>
using namespace std;

int main() {
    int low, high, i;
    bool isPrime = true;

    cout << "Enter two numbers (intervals): ";
    cin >> low >> high;

    cout << "\nPrime numbers between " << low << " and " << high << " are: " << endl;

    while (low < high) {
        isPrime = true;
        if (low == 0 || low == 1) {
            isPrime = false;
        }
        else {
            for (i = 2; i <= low / 2; ++i) {
                if (low % i == 0) {
                    isPrime = false;
                    break;
                }
            }
        }
        
        if (isPrime)
            cout << low << " ";

        ++low;
    }

    return 0;
}

Output
Enter two numbers (intervals): 0 20

Prime numbers between 0 and 20 are: 
2 3 5 7 11 13 17 19

Display Prime Numbers When Larger Number is Entered first

#include <iostream>
using namespace std;

int main()
{
    int low, high, temp, i;
    bool isPrime;
    
    cout << "Enter two numbers (intevals): ";
    cin >> low >> high;

    //swapping numbers if low is greater than high
    if (low > high) {
        temp = low;
        low = high;
        high = temp;
    }
    cout << "\nPrime numbers between " << low << " and " << high << " are:" << endl;

    while (low < high) {
        isPrime = true;
        if (low == 0 || low == 1) {
            isPrime = false;
        }
        else {
            for (i = 2; i <= low / 2; ++i) {
                if (low % i == 0) {
                    isPrime = false;
                    break;
                }
            }
        }

        if (isPrime)
            cout << low << " ";

        ++low;
    }
    return 0;
}

Output
Enter two numbers (intervals): 20 0

Prime numbers between 0 and 20 are: 
2 3 5 7 11 13 17 19

Display all Factors of a Number

#include <iostream>
using namespace std;

int main() {
    int n, i;

    cout << "Enter a positive integer: ";
    cin >> n;

    cout << "Factors of " << n << " are: ";  
    for(i = 1; i <= n; ++i) {
        if(n % i == 0)
            cout << i << " ";
    }

    return 0;
}

Output
Enter a positive integer: 60
Factors of 60 are: 1 2 3 4 5 6 10 12 15 20 30 60

Check Prime Number

#include <iostream>
using namespace std;

bool checkPrimeNumber(int);

int main() {
    int n;

    cout << "Enter a positive  integer: ";
    cin >> n;

    if (checkPrimeNumber(n))
        cout << n << " is a prime number.";
    else
        cout << n << " is not a prime number.";
    return 0;
}

bool checkPrimeNumber(int n) {
    bool isPrime = true;

    // 0 and 1 are not prime numbers
    if (n == 0 || n == 1) {
        isPrime = false;
    }
    else {
        for (int i = 2; i <= n / 2; ++i) {
            if (n % i == 0) {
                isPrime = false;
                break;
            }
        }
    }
    return isPrime;
}

Output
Enter a positive  integer: 23
23 is a prime number.

Calculate Sum of Natural numbers using Recursion

#include<iostream>
using namespace std;

int add(int n);

int main() {
    int n;

    cout << "Enter a positive integer: ";
    cin >> n;

    cout << "Sum =  " << add(n);

    return 0;
}

int add(int n) {
    if(n != 0)
        return n + add(n - 1);
    return 0;
}

Output
Enter an positive integer: 10
Sum = 55

Program to convert binary number to decimal

#include <iostream>
#include <cmath>

using namespace std;

int convertBinaryToDecimal(long long);

int main()
{
    long long n;

    cout << "Enter a binary number: ";
    cin >> n;
 
    cout << n << " in binary = " << convertBinaryToDecimal(n) << "in decimal";
    return 0;
}

int convertBinaryToDecimal(long long n)
{
    int decimalNumber = 0, i = 0, remainder;
    while (n!=0)
    {
        remainder = n%10;
        n /= 10;
        decimalNumber += remainder*pow(2,i);
        ++i;
    }
    return decimalNumber;
}

Output
Enter a binary number: 1111
1111 in binary = 15

Program to convert decimal number to binary

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

long long convertDecimalToBinary(int);

int main()
{
    int n, binaryNumber;

    cout << "Enter a decimal number: ";
    cin >> n;
    binaryNumber = convertDecimalToBinary(n);
    cout << n << " in decimal = " << binaryNumber << " in binary" << endl ;
    return 0;
}

long long convertDecimalToBinary(int n)
{
    long long binaryNumber = 0;
    int remainder, i = 1, step = 1;

    while (n!=0)
    {
        remainder = n%2;
        cout << "Step " << step++ << ": " << n << "/2, Remainder = " << remainder << ", Quotient = " << n/2 << endl;
        n /= 2;
        binaryNumber += remainder*i;
        i *= 10;
    }
    return binaryNumber;
}

output
Enter a decimal number: 19
Step 1: 19/2, Remainder = 1, Quotient = 9
Step 2: 9/2, Remainder = 1, Quotient = 4
Step 3: 4/2, Remainder = 0, Quotient = 2
Step 4: 2/2, Remainder = 0, Quotient = 1
Step 5: 1/2, Remainder = 1, Quotient = 0
19 in decimal = 10011 in binary

Convert Octal Number to Decimal

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

int octalToDecimal(int octalNumber);

int main()
{
   int octalNumber;
   cout << "Enter an octal number: ";
   cin >> octalNumber;
   cout << octalNumber << " in octal = " << octalToDecimal(octalNumber) << " in decimal";
   
   return 0;
}

// Function to convert octal number to decimal
int octalToDecimal(int octalNumber)
{
    int decimalNumber = 0, i = 0, rem;
    while (octalNumber != 0)
    {
        rem = octalNumber % 10;
        octalNumber /= 10;
        decimalNumber += rem * pow(8, i);
        ++i;
    }
    return decimalNumber;
}

Output
Enter an octal number: 2341
2341 in octal = 1249 in decimal

Convert Decimal Number to Octal

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

int decimalToOctal(int decimalNumber);

int main()
{
   int decimalNumber;
   cout << "Enter a decimal number: ";
   cin >> decimalNumber;
   cout << decimalNumber << " in decimal = " << decimalToOctal(decimalNumber) << " in octal";
   
   return 0;
}

// Function to convert decimal number to octal
int decimalToOctal(int decimalNumber)
{
    int rem, i = 1, octalNumber = 0;
    while (decimalNumber != 0)
    {
        rem = decimalNumber % 8;
        decimalNumber /= 8;
        octalNumber += rem * i;
        i *= 10;
    }
    return octalNumber;
}

Output
Enter an decimal number: 78
78 in decimal = 116 in octal

Program to Convert Binary to Octal

#include <iostream>
#include <cmath>

using namespace std;

int convertBinarytoOctal(long long);
int main()
{
    long long binaryNumber;

    cout << "Enter a binary number: ";
    cin >> binaryNumber;

    cout << binaryNumber << " in binary = " << convertBinarytoOctal(binaryNumber) << " in octal ";

    return 0;
}

int convertBinarytoOctal(long long binaryNumber)
{
    int octalNumber = 0, decimalNumber = 0, i = 0;

    while(binaryNumber != 0)
    {
        decimalNumber += (binaryNumber%10) * pow(2,i);
        ++i;
        binaryNumber/=10;
    }

    i = 1;

    while (decimalNumber != 0)
    {
        octalNumber += (decimalNumber % 8) * i;
        decimalNumber /= 8;
        i *= 10;
    }

    return octalNumber;
}

Output
Enter a binary number: 10001
10001 in binary = 21 in octal

Program to Convert Octal to Binary

#include <iostream>
#include <cmath>

using namespace std;

long long convertOctalToBinary(int);
int main()
{
    int octalNumber;

    cout << "Enter an octal number: ";
    cin >> octalNumber;

    cout << octalNumber << " in octal = " << convertOctalToBinary(octalNumber) << "in binary";

    return 0;
}

long long convertOctalToBinary(int octalNumber)
{
    int decimalNumber = 0, i = 0;
    long long binaryNumber = 0;

    while(octalNumber != 0)
    {
        decimalNumber += (octalNumber%10) * pow(8,i);
        ++i;
        octalNumber/=10;
    }

    i = 1;

    while (decimalNumber != 0)
    {
        binaryNumber += (decimalNumber % 2) * i;
        decimalNumber /= 2;
        i *= 10;
    }

    return binaryNumber;
}

Output
Enter an octal number: 54
54 in octal = 101100

Reverse a sentence using recursion.

#include <iostream>
using namespace std;

// function prototype
void reverse(const string& a);

int main() {
  string str;

  cout << " Please enter a string " << endl;
  getline(cin, str);
    
  // function call
  reverse(str);

  return 0;    
}

// function definition
void reverse(const string& str) {

  // store the size of the string
  size_t numOfChars = str.size();

  if(numOfChars == 1) {
    cout << str << endl;
  }
  else {
    cout << str[numOfChars - 1];

    // function recursion
    reverse(str.substr(0, numOfChars - 1));
  }
}

Output
Enter a sentence: margorp emosewa
awesome program

Calculate Average of Numbers Using Arrays

#include <iostream>
using namespace std;

int main()
{
    int n, i;
    float num[100], sum=0.0, average;

    cout << "Enter the numbers of data: ";
    cin >> n;

    while (n > 100 || n <= 0)
    {
        cout << "Error! number should in range of (1 to 100)." << endl;
        cout << "Enter the number again: ";
        cin >> n;
    }

    for(i = 0; i < n; ++i)
    {
        cout << i + 1 << ". Enter number: ";
        cin >> num[i];
        sum += num[i];
    }

    average = sum / n;
    cout << "Average = " << average;

    return 0;
}

Output
Enter the numbers of data: 6
1. Enter number: 45.3
2. Enter number: 67.5
3. Enter number: -45.6
4. Enter number: 20.34
5. Enter number: 33
6. Enter number: 45.6
Average = 27.69

Find Largest Element of an Array

#include <iostream>
using namespace std;

int main()
{
    int i, n;
    float arr[100];

    cout << "Enter total number of elements(1 to 100): ";
    cin >> n;
    cout << endl;

    // Store number entered by the user
    for(i = 0; i < n; ++i)
    {
       cout << "Enter Number " << i + 1 << " : ";
       cin >> arr[i];
    }

    // Loop to store largest number to arr[0]
    for(i = 1;i < n; ++i)
    {
       // Change < to > if you want to find the smallest element
       if(arr[0] < arr[i])
           arr[0] = arr[i];
    }
    cout << "Largest element = " << arr[0];

    return 0;
}

output
Enter total number of elements: 8

Enter Number 1: 23.4
Enter Number 2: -34.5
Enter Number 3: 50
Enter Number 4: 33.5
Enter Number 5: 55.5
Enter Number 6: 43.7
Enter Number 7: 5.7
Enter Number 8: -66.5

Largest element = 55.5

Calculate Standard Deviation

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

float calculateSD(float data[]);

int main()
{
    int i;
    float data[10];

    cout << "Enter 10 elements: ";
    for(i = 0; i < 10; ++i)
        cin >> data[i];

    cout << endl << "Standard Deviation = " << calculateSD(data);

    return 0;
}

float calculateSD(float data[])
{
    float sum = 0.0, mean, standardDeviation = 0.0;

    int i;

    for(i = 0; i < 10; ++i)
    {
        sum += data[i];
    }

    mean = sum/10;

    for(i = 0; i < 10; ++i)
        standardDeviation += pow(data[i] - mean, 2);

    return sqrt(standardDeviation / 10);
}

output
Enter 10 elements: 1
2
3
4
5
6
7
8
9
10

Standard Deviation = 2.872281

Add Two Matrix Using Multi-dimensional Arrays

#include <iostream>
using namespace std;

int main()
{
    int r, c, a[100][100], b[100][100], sum[100][100], i, j;

    cout << "Enter number of rows (between 1 and 100): ";
    cin >> r;

    cout << "Enter number of columns (between 1 and 100): ";
    cin >> c;

    cout << endl << "Enter elements of 1st matrix: " << endl;

    // Storing elements of first matrix entered by user.
    for(i = 0; i < r; ++i)
       for(j = 0; j < c; ++j)
       {
           cout << "Enter element a" << i + 1 << j + 1 << " : ";
           cin >> a[i][j];
       }

    // Storing elements of second matrix entered by user.
    cout << endl << "Enter elements of 2nd matrix: " << endl;
    for(i = 0; i < r; ++i)
       for(j = 0; j < c; ++j)
       {
           cout << "Enter element b" << i + 1 << j + 1 << " : ";
           cin >> b[i][j];
       }

    // Adding Two matrices
    for(i = 0; i < r; ++i)
        for(j = 0; j < c; ++j)
            sum[i][j] = a[i][j] + b[i][j];

    // Displaying the resultant sum matrix.
    cout << endl << "Sum of two matrix is: " << endl;
    for(i = 0; i < r; ++i)
        for(j = 0; j < c; ++j)
        {
            cout << sum[i][j] << "  ";
            if(j == c - 1)
                cout << endl;
        }

    return 0;
}

Output
Enter number of rows (between 1 and 100): 2
Enter number of columns (between 1 and 100): 2

Enter elements of 1st matrix:
Enter element a11: -4
Enter element a12: 5
Enter element a21: 6
Enter element a22: 8

Enter elements of 2nd matrix:
Enter element b11: 3
Enter element b12: -9
Enter element b21: 7
Enter element b22: 2

Sum of two matrix is:
-1   -4
13   10

Multiply Two Matrix Using Multi-dimensional Arrays

#include <iostream>
using namespace std;

int main()
{
    int a[10][10], b[10][10], mult[10][10], r1, c1, r2, c2, i, j, k;

    cout << "Enter rows and columns for first matrix: ";
    cin >> r1 >> c1;
    cout << "Enter rows and columns for second matrix: ";
    cin >> r2 >> c2;

    // If column of first matrix in not equal to row of second matrix,
    // ask the user to enter the size of matrix again.
    while (c1!=r2)
    {
        cout << "Error! column of first matrix not equal to row of second.";

        cout << "Enter rows and columns for first matrix: ";
        cin >> r1 >> c1;

        cout << "Enter rows and columns for second matrix: ";
        cin >> r2 >> c2;
    }

    // Storing elements of first matrix.
    cout << endl << "Enter elements of matrix 1:" << endl;
    for(i = 0; i < r1; ++i)
        for(j = 0; j < c1; ++j)
        {
            cout << "Enter element a" << i + 1 << j + 1 << " : ";
            cin >> a[i][j];
        }

    // Storing elements of second matrix.
    cout << endl << "Enter elements of matrix 2:" << endl;
    for(i = 0; i < r2; ++i)
        for(j = 0; j < c2; ++j)
        {
            cout << "Enter element b" << i + 1 << j + 1 << " : ";
            cin >> b[i][j];
        }

    // Initializing elements of matrix mult to 0.
    for(i = 0; i < r1; ++i)
        for(j = 0; j < c2; ++j)
        {
            mult[i][j]=0;
        }

    // Multiplying matrix a and b and storing in array mult.
    for(i = 0; i < r1; ++i)
        for(j = 0; j < c2; ++j)
            for(k = 0; k < c1; ++k)
            {
                mult[i][j] += a[i][k] * b[k][j];
            }

    // Displaying the multiplication of two matrix.
    cout << endl << "Output Matrix: " << endl;
    for(i = 0; i < r1; ++i)
    for(j = 0; j < c2; ++j)
    {
        cout << " " << mult[i][j];
        if(j == c2-1)
            cout << endl;
    }

    return 0;
}

Output
Enter rows and column for first matrix: 3
2
Enter rows and column for second matrix: 3
2
Error! column of first matrix not equal to row of second.

Enter rows and column for first matrix: 2
3
Enter rows and column for second matrix: 3
2

Enter elements of matrix 1:
Enter elements a11: 3
Enter elements a12: -2
Enter elements a13: 5
Enter elements a21: 3
Enter elements a22: 0
Enter elements a23: 4

Enter elements of matrix 2:
Enter elements b11: 2
Enter elements b12: 3
Enter elements b21: -9
Enter elements b22: 0
Enter elements b31: 0
Enter elements b32: 4

Output Matrix:
24 29
6  25

Find the Number of Vowels, Consonants, Digits and White Spaces in a String

#include <iostream>
using namespace std;

int main()
{
    char line[150];
    int vowels, consonants, digits, spaces;

    vowels =  consonants = digits = spaces = 0;

    cout << "Enter a line of string: ";
    cin.getline(line, 150);
    for(int i = 0; line[i]!='\0'; ++i)
    {
        if(line[i]=='a' || line[i]=='e' || line[i]=='i' ||
           line[i]=='o' || line[i]=='u' || line[i]=='A' ||
           line[i]=='E' || line[i]=='I' || line[i]=='O' ||
           line[i]=='U')
        {
            ++vowels;
        }
        else if((line[i]>='a'&& line[i]<='z') || (line[i]>='A'&& line[i]<='Z'))
        {
            ++consonants;
        }
        else if(line[i]>='0' && line[i]<='9')
        {
            ++digits;
        }
        else if (line[i]==' ')
        {
            ++spaces;
        }
    }

    cout << "Vowels: " << vowels << endl;
    cout << "Consonants: " << consonants << endl;
    cout << "Digits: " << digits << endl;
    cout << "White spaces: " << spaces << endl;

    return 0;
}

Output
Enter a line of string: This is 1 hell of a book.
Vowels: 7
Consonants: 10
Digits: 1
White spaces: 6

++ Increment Operator Overloading with no return

#include <iostream>
using namespace std;

class Check
{
    private:
       int i;
    public:
       Check(): i(0) {  }
       void operator ++() 
          { ++i; }
       void Display() 
          { cout << "i=" << i << endl; }
};

int main()
{
    Check obj;

    // Displays the value of data member i for object obj
    obj.Display();

    // Invokes operator function void operator ++( )
    ++obj; 
  
    // Displays the value of data member i for object obj
    obj.Display();

    return 0;
}

Output
i=0
i=1