C++ Tutorial Index

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C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++

C++ Prime number program

In this lesson, you'll learn how to verify whether a given number is a prime number or not in C++, and you'll obtain code to do it.

What is the definition of a prime number ? 

A prime number is any number that is bigger than one and should be divided by one or divided by itself. Since prime numbers could not be divided by any other integer, so only the same number or 1 should be used to do so.

For Example : 2, 3, 5, 7 and so on.

You might be wondering why the number 2 is considered a prime number. Since 2 seems to be the only prime number that is also even, it is an exception. Only two integers are prime and successive natural numbers! In addition, the number 2 is the smallest prime number.

Checking for a prime number :

If a number n, is divisible by any integer between 2 to one less than (n-1), it is not a prime number, otherwise it is.

Example :

#include <iostream>
using namespace std;


int main()
{
    /* Defining and initializing a variable */   
    int num, j, k = 0;
    
    /* Getting the input from the user */
    cout << "Enter a number : "; cin>>num;
    
    for (j = 1; j <= num; j++)
    {
        if (num % j == 0)
        {
           k++;
        }
    }
    if (k == 2)
    {
       cout << "It’s a Prime number" << endl;
    }
    else
    {
         cout << "It’s not a Prime number" << endl; 
    }
    return 0;    
}

Output :

Enter a number : 5
It’s a Prime number 

Explanation :

To begin, you must contain the iostream header file using the "include" directive followed by a #, which indicates that the header file must be processed before compilation, hence the name pre-processor directive. You may now utilize the namespace statement within a program to resolve naming conflicts.

Next, define three integer type variables, 'num', j and 'k,' and set k to 0. Using the cout""; command, inform the user to input any natural number num. The 'cin' command takes a value from the input device (in this case, the keyboard) and stores it in the variable num. You must now create a for - loop that will count from 1 to num. And within this loop, we verify whether dividing num by j yields a result of 0 or not. If the condition is met, the value of c is increased.

Now, if k == 2, it prints "It’s a Prime number" and if k is not equal to 2, it publishes "It’s not a Prime number". Finally, we get the required output.

Example 2 :

#include <iostream>
using namespace std;
int main()
{
int low, high, fl, temp;
cout << "Please enter ant two numbers to find the prime numbers between those numbers : "<< endl;
cin >> low >> high;


if ( low > high) {    //the numbers will be swapped when the low number will be greater than the high number. //
temp = low;
low = high;
high = temp;
}
cout << "The Prime numbers between " << low << " and " << high << " are : "<< endl;


while ( low < high)
{
fl = 0;
for ( int x = 2; x <= low/2; ++x)
{
if ( low % x == 0)
{
fl = 1;
break;
}
}
if ( fl == 0)
cout << low << " ";
++low;
}
return 0;
}

Output :

Please enter ant two numbers to find the prime numbers between those numbers :
11
20 
The Prime numbers between 11 and 20 are : 
11 13 17 19

Explanation :

We used integers as a low number, a high number, a temp variable, and a flag fl in the code above. We begin by taking two integers as input, one of which is low and the other high. If the low number is greater than the high number, the numbers will be switched using a temp variable before proceeding with the function. Now, the while loop will continue until low is less than high, and the for loop will continue to calculate prime numbers between them, resulting in printing all the prime number between low and high.

Summary :

Prime number reasoning may be applied in any computer language, not only C++. This reasoning may be used to locate a group of prime numbers according to criteria in seconds without spending any time in computer programming, from a small collection of numbers to a large number of numbers.



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