/*------------------------------------------------------------------------------
SIEVE.C: Eratosthenes Sieve Prime Number Program in C from Byte Jan 1983.
------------------------------------------------------------------------------*/
#include
#include
#include
#define TRUE 1
#define FALSE 0
#define SIZE 8190
char xdata flags[SIZE+1];
/*------------------------------------------------
------------------------------------------------*/
void main (void) {
register int i,k;
int prime,count,iter;
/*------------------------------------------------
Setup the serial port for 1200 baud at 16MHz.
------------------------------------------------*/
SCON = 0x50; /* SCON: mode 1, 8-bit UART, enable rcvr */
TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */
TH1 = 221; /* TH1: reload value for 1200 baud @ 16MHz */
TR1 = 1; /* TR1: timer 1 run */
TI = 1; /* TI: set TI to send first char of UART */
/*------------------------------------------------
Th following code is an implementation of the
Sieve of Eratosthenes.
------------------------------------------------*/
printf("10 iterations\n");
for (iter = 1; iter {
P1 = iter; /* output iter on P1 */
count = 0; /* initialize prime counter */
for (i = 0; i flags[i] = TRUE;
for (i = 0; i {
if (flags[i]) /* found a prime */
{
prime = i + i + 3; /* twice index + 3 */
for (k = i + prime; k flags[k] = FALSE; /* kill all multiples */
count++; /* primes found */
}
}
}
printf("%d primes.\n",count); /* primes found in 10th pass */
while (1);
}
