How to write a logic for detecting a prime number?

Prime numbers are those positive numbers which are only divisible by 1 and the number itself. A simple logic can be written to check this like starting iteration with 2 to (number -1) and inside this we check if number is divisible. If it completes all iterations and found not divisible by any number in the range then it is a prime number.

 #define TRUE 1

 #define FALSE 0

 bool is_prime(unsigned int number)

 {

   unsigned int i;

   for (i = 2; i < number; i++)

   {

     if((number%i) ==0) 

       return FALSE;

   }

   return TRUE;

 }

Print all prime numbers in a given range

 
 int main(int argc, char* argv[])

 {

   unsigned int index;

   unsigned int range;

   printf("Print Prime numbers till #");

   scanf("%u", &range);

   for(index = 1; index <= range; index++)

   {

     if(is_prime(index) != FALSE){

       printf("%u,", index);

     }

   }

   printf("\b.");

   return 0;

 }

 Output:

 Print Prime numbers till #50

 1,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47.

Print first n-number of prime numbers

 
 int main(int argc, char* argv[])

 {

   unsigned int index;

   unsigned int count;

   printf("\nHow many prime no to print #");

   scanf("%u", &count);

   for(index = 1; count > 0; index++)

   {

     if(is_prime(index) != FALSE){

       printf("%u,", index);

       count--;

     }

   }

   printf("\b.");

   return 0;

 }

 Output:

 How many prime no to print #10

 1,2,3,5,7,11,13,17,19,23.

About our authors: Team EQA

You have viewed 1 page out of 248. Your C learning is 0.00% complete. Login to check your learning progress.

‹ # ›