README.md

Description

How many prime numbers are there between 1 and X? You just have to choose X and this program will do the rest. Click Luke to go to my Web Page: other source code available...

More Info

an integer number

the number of prime numbers lower than X

Submitted On
By	Luke
Level	Beginner
User Rating	3.3 (10 globes from 3 users)
Compatibility	C
Category	Math
World	C / C++
Archive File

Source Code

/*
 Save this file as lcpri.c
*/
#include <stdio.h>
#include <stdlib.h>
int main()
{
 ldiv_t dividi;
 int n, totprimi, primo;
 int cont1, cont2;
 printf("\n\tEnter an integer (>= 1): ");
 scanf("%d", &n);
 if (n < 1)
 {
 printf("\n\t...I said >= 1...bye!\n");
 return(-1);
 }
 totprimi = 0;
 for(cont1 = 1; cont1 < n; cont1++)
 {
 primo = 1;
 for(cont2 = 2; cont2 <= (cont1 / 2); cont2++)
 {
  dividi = ldiv(cont1, cont2);
  if (dividi.rem == 0)
  {
  primo = 0;
  break;
  }
 }
 if (primo) ++totprimi;
 }
 printf("\n\tThere are %d prime numbers lower than %d\n", totprimi, n);
 return 0;
}