why the results i run or debug this code are different,your help would be appreciated

/*
* control.c
*
* Created on: 2012-11-15
* Author: zhanghan
*/


#include "alt_types.h"
#include "altera_avalon_timer_regs.h"
#include "sys/alt_irq.h"
#include "system.h"
#include <stdio.h>
#include <unistd.h>


void timer_ISR(void);
void init_spi(void);
int d;


int main(void)
{

printf("\nWelcome!!!\n");

init_spi();


printf("\nSpi initial succeed!\n");


while(1)
{
}
return 0;


}
void init_spi(void)
{
d=0;
IOWR_ALTERA_AVALON_TIMER_STATUS(TIMER_BASE,0x00);
// IOWR_ALTERA_AVALON_TIMER_PERIODH(TIMER_BASE,25000> >16);
// IOWR_ALTERA_AVALON_TIMER_PERIODL(TIMER_BASE,25000 && 0xffff);
IOWR_ALTERA_AVALON_TIMER_CONTROL(TIMER_BASE,0x07); //start the timer
alt_irq_register(TIMER_IRQ,(void*)TIMER_BASE,(void *)timer_ISR);
}


//interrupt service routine


void timer_ISR(void)
{
printf("\nthe data is %d \n" ,d);
d++;
IOWR_ALTERA_AVALON_TIMER_STATUS(TIMER_BASE, 0x00); //clear the timeout bit
}