Prime Numbers
A prime number is an integer greater than 1 that has exactly two divisors, 1 and itself.
The first ten prime numbers are

• 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.

Integers that are not prime are called composite numbers.
C program to find prime numbers in a given range

/**
C program to find prime numbers in a given range by codebind.com
*/

#include<stdio.h>
#include<conio.h>

int main()
{
  int num,i,count,n;
  printf("Enter max range: ");
  scanf("%d",&n);
  for(num = 1;num<=n;num++){
    count = 0;
    for(i=2;i<=num/2;i++){
      if(num%i==0){
        count++;
        break;
      }
    }

    if(count==0 && num!= 1)
      printf("%d ",num);
  }
  return 0;
}

/*
OUTPUT:
Enter max range: 30
2  3  5  7 11 13 17 19 23 29
*/

C Program to Check If the number is Prime or not

/**
C Program to Check If the number is Prime or not by codebind.com
*/

#include<stdio.h>
#include<conio.h>

#include <iostream>

using namespace std;

int main() {
  int i,number;
  printf("Enter any num: ");
  scanf("%d", &number);
  if(number == 1) {
    printf("Smallest prime num is 2");
  }
  for(i=2;i<number;i++) {
    if(number%i == 0) {
      printf("Not prime number");
      break;
    }
  }
  if(number == i) {
    printf("Yes, Number is Prime");
  }
  return 0;
}

/*
OUTPUT:
Enter any num: 17
Yes, Number is Prime
*/