Question

Write a program in C++ to check whether a number is prime or not

Answer 1

#include<iostream>

using namespace std;

int main(){

int num,i,n=0, flag=0; /*we take num as a variable where value is take. we set flag to 0*/

cout<<"Enter the number:"; /*take input like 19*/

cin>>num;

n=num/2; /*first we divide by 2 if we divide 19 by 2 it provide 9*/

for(i=2;i<=n;i++) /*we start loop by 2 and it goes upto 9*/

{

if(num%i==0) /*19%2 its remainder 1 then loop increase by 1 now 19%3 then return 1 then it work upto 19%9 then again return 1 . now flag is 0 */

{

cout<<"Number is not Prime."<<endl;  

          flag=1;  

          break;  

}

}

if (flag==0) /*it Show prime number*/

      cout << "Your number is Prime."<<endl;  

  return 0;  

}

Output: Enter the number:19

Your number is prime.

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