plz query this program

#include <At89x52.h> /* special function register declarations */
#include <stdio.h> /* prototype declarations for I/O functions */

void main (void) {
/*------------------------------------------------
Setup the serial port for 9600 baud at 11.0592MHz.
------------------------------------------------*/

TR1 = 0;
SCON = 0x50; /* SCON: mode 1, 8-bit UART, enable rcvr */
TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */
PCON &= 0x7F;
TH1 = 0xFD; /* TH1: reload value for 9600 baud @ 11.0592MHz */
// EA = 1;
// ES = 1;
RI = 1;
TI = 1;
TR1 = 1;
/*------------------------------------------------
Note that an embedded program never exits (because
there is no operating system to return to). It
must loop and execute forever.
------------------------------------------------*/

printf ("hallo\r"); <=- with this line it doesn't work anymore !!!!!!!!!!!!!!!!!
while (1) {
TI = 0;
SBUF = 'A';
while (!TI);
P1 ^= 0xFF;
TI=0;
SBUF = '*';
while (!TI);
TI=0;
SBUF = '\r';
while (!TI);
} }

i dont understand the program below the haloo line. plz give the details