C++ example to check whether a Number is Prime or Not
In this tutorial, we will discuss the concept of C++ example to check whether a Number is Prime or Not
In this post, we are going to learn how to check a number is prime or not using for, while and do-while loop in C++ programming language with Example program
Prime number
The number that can be divided by 1 and itself. it is called prime number
for Example 2,3,5,7,11,13…
C++ example to check a Number is Prime or Not
To understand this example programs, you should have previous knowledge of following C++ topics
Check the prime number using for loop
Program 1
#include <iostream>
#include <conio.h>
using namespace std;
int main()
{
int num,i,count=0;
cout<<"Enter the positive integer\n";
//Takes input from user
cin>>num;
for(i=2; i<=num/2; i++){
//condition for non-prime
if(num%i==0)
{
count=1;
break;
}
}
if(num==1){
cout<<"you entered"<<num<<"\n";
cout<<num<<" is neither a prime nor a composite number ";
}
else{
if(count==0){
cout<<"you entered" <<num<<"\n\n";
cout<<num<<" is a prime number ";
}
else{
cout<<"you entered: " <<num<<"\n\n";
cout<<num<<" is not a prime number ";
}
}
getch();
return 0;
}
When the above code is executed, it produces the following results
Case 1
Enter the positive integer 45 you entered: 45 45 is not a prime number
Case 2
Enter the positive integer 43 you entered: 43 43 is a prime number
Case 3
Enter the positive integer 1 you entered 1 i is neither a prime nor a composite number
This program allows the user to enter a positive number and then it will check the given number is a prime number or not using for loop in C++ language
Check the prime number using while loop
Program 2
#include <iostream>
#include <conio.h>
using namespace std;
int main()
{
int num,i,count=0;
cout<<"Enter the positive integer\n";
//Takes input from user
cin>>num;
i=2;
while(i<=num/2){
//condition for non-prime
if(num%i==0)
{
count=1;
break;
}
i++;
}
if(num==1){
cout<<"you entered "<<num<<"\n";
cout<<num<<" is neither a prime nor a composite number ";
}
else{
if(count==0){
cout<<"you entered" <<num<<"\n\n";
cout<<num<<" is a prime number ";
}
else{
cout<<"you entered" <<num<<"\n\n";
cout<<num<<" is not a prime number ";
}
}
getch();
return 0;
}
When the above code is executed, it produces the following results
Case 1
Enter the positive integer 99 you entered: 99 99 is not a prime number
Case 2
Enter the positive integer 97 you entered: 97 97 is a prime number
Case 3
Enter the positive integer 1 you entered 1 i is neither a prime nor a composite number
This program allows the user to enter a positive number and then it will check the given number is a prime number or not using while loop in C++ language
Check the prime number using the do-while loop
Program 3
#include <iostream>
#include <conio.h>
using namespace std;
int main()
{
int num,i,count=0;
cout<<"Enter the positive integer\n";
//Takes input from user
cin>>num;
i=2;
do{
//condition for non-prime
if(num%i==0)
{
count=1;
break;
}
i++;
}while(i<=num/2);
if(num==1){
cout<<"you entered "<<num<<"\n";
cout<<num<<" is neither a prime nor a composite number ";
}
else{
if(count==0){
cout<<"you entered" <<num<<"\n\n";
cout<<num<<" is a prime number ";
}
else{
cout<<"you entered" <<num<<"\n\n";
cout<<num<<" is not a prime number ";
}
}
getch();
return 0;
}
When the above code is executed, it produces the following results
Case 1
Enter the positive integer 190 you entered: 190 190 is not a prime number
Case 2
Enter the positive integer 199 you entered: 199 199 is a prime number
Case 3
Enter the positive integer 1 you entered 1 i is neither a prime nor a composite number
This program allows the user to enter a positive number and then it will check the given number is a prime number or not using the do-while loop in C++ language
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