external_4.c (713B)
1 // 4. Write a function to find whether a given number is prime or not. Use it to generate prime numbers less than 100. 2 3 #include<stdio.h> 4 5 int isPrime(int); 6 7 int main() { 8 int num, i; 9 printf("Enter the number: "); 10 scanf("%d", &num); 11 if(isPrime(num)) printf("\n%d is a prime number.", num); 12 else printf("\n%d is not a prime number.", num); 13 14 // generate prime numbers upto 100 15 printf("\n\nPrime number upto 100: "); 16 for(i = 1; i <= 100; i++) { 17 if(isPrime(i)) printf("\n%d ", i); 18 } 19 return 0; 20 } 21 22 int isPrime(int n) { 23 int i; 24 if(n == 2) return 1; 25 if(n <= 1 || n % 2 == 0) return 0; 26 for(i = 3; i * i <= n; i = i+2) if(n % i == 0) return 0; 27 return 1; 28 }