rtx tiny

#include <reg51.h>
#include <rtx51tny.h>
#include <stdio.h>
unsigned char global;
void First (void) _task_ 0
{
os_create_task(1);
os_create_task(2);
os_delete_task(0);
}
void Second (void) _task_ 1
{
while(1)
{
global++;
if(global==0)
os_send_signal(2);
}

}
void Third (void) _task_ 2
{
while(1)
{
os_wait(K_SIG,0,0);
printf("%s","thank you!\n");
}
}
complier and linker very well,but I can't go it,if I go,display "
*** error 65: access violation at I:0xFE : no 'write' permission",why??