Description

A number is called prime if it is divisible by 1 and number itself. To check the number 
is prime, check the number is divisible any number from 2 to half of the number.

C/C++

/* C Program to Check Whether a Number is Prime or Not */
//Save it as CheckPrime.c

#include<stdio.h>
int main(){

    int i, number, flag=0;

    printf("Enter a number : ");
    scanf("%d",&number);

    
    //Traverse from 2 to half of the number
    
    for(i=2;i<=(number/2);i++){
        
        /*If number is divisible by any of the number then
          it is composite and come out of the loop*/
         
        if(number%i == 0){
            flag=1;
            break;
        }
    }

    if(number==1){
        printf("The number is neither prime nor composite");
    }
    else{
        if(flag==1){
            printf("The number is not a prime number");
        }
        else{
            printf("The number is a prime number");
        }
    }
    return 0;
}

Input:
Enter a number : 
7

Output:
The number is a prime number

Java

/* Java Program to Check Whether a Number is Prime or Not */
//Save it as CheckPrime.java

import java.io.*;
import java.util.Scanner;

public class CheckPrime {

    public static void main(String[] args) {
        
        Scanner scanner = new Scanner(System.in);
        
        int i, number, flag=0;

        System.out.println("Enter a number : ");
        number = scanner.nextInt();

        
        //Traverse from 2 to half of the number
        
        for(i=2;i<=(number/2);i++){
            
            /*If number is divisible by any of the number then
              it is composite and come out of the loop*/
            
            if(number%i == 0){
                flag=1;
                break;
            }
        }

        if(number==1){
            System.out.print("The number is neither prime nor composite");
        }
        else{
            if(flag==1){
                System.out.print("The number is not a prime number");
            }
            else{
                System.out.print("The number is prime number");
            }
        }
    }
}

Input:
Enter a number : 
4

Output:
The number is not a prime number

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