To check whether a number is prime or not?

C++ program to find a number is prime or not?

Algorithm:

Input = number

set counter=0;

set i=0 to i<=number

if(number%i==0)
counter=counter+1;
 i=i+1;
if(counter == 2)
print"number is prime";

else
print "number is not prime";
    
exit;
    

Approach to solve:

Input = 5;

number%i=5%1=0

5%2=1

5%3=2

5%4=1

5%5=0

counter=2

so, it will print number is prime.

Input =4

number%i=4%1=0

4%2=0

4%3=1

4%4=0

counter=3

so, it will print number is not prime.

Program:-

#include<iostream>

using namespace std;
//function for prime number
int prime(int num){
 
 int count=0;
 if(num==1){
  return 0;
 }
 
 for(int i=1; i<=num; i++){
  
   if(num%i==0)
     count++;
 }
 
 if(count==2){
  cout<<"Number is Prime ";
 }
 
 else
 {
  cout<<"Number is not prime ";
 }
 
}

int main(){
 
 int num1;
 
 cout<<"Enter any number:";
 cin>>num1;
 
 prime (num1);  //function calling
 
 return 0;
}

Output:-

Enter any number:3
Number is prime

Enter any number:88
Number is not prime

HAPPY CODING...