Write a program that accepts a positive integer as input and then displays all the prime numbers smaller than or equal to that number. - C Data Type

Description

Write a program that accepts a positive integer as input and then displays all the prime numbers smaller than or equal to that number.

Demo Code

#include <stdio.h>
#include <stdbool.h>

void flush_input_buffer(void);

int main(void){
  bool prime_flag;
  int limit;/* w w w. j a v a  2 s.  c  o  m*/
  printf("Enter a positive integer: \n");

  while (scanf("%d", &limit) != 1 || limit < 1){
    flush_input_buffer();
    printf("Enter a positive integer: \n");
  }

  for (int i = 2; i <= limit; i++){
    prime_flag = true;
    for (int j = 2; j < i; j++) // for all j less than i ...
    {
      if (i % j == 0) // if i is divisible by j ...
      {
        prime_flag = false; // then i is not prime
        break; // break out of inner loop
      }
    }
    if (prime_flag)
      printf("%d is prime.\n", i);
  }

  return 0;
}

void flush_input_buffer(void)
{
  while (getchar() != '\n')
    ;
}

Result

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