Error during simulation

hi,

i have just started learning Keil simulation . I tried with simple programs and I tried the below one:

#include<reg51.h>
void main(void)
{ unsigned char z; for(z=0;z<100;z++) P1 = z;
}

while executing the simulation i am getting the following error:
*** error 65: access violation at C:0x6400 : no 'execute/read' permission

Kindly help me in getting rid of this error and that why is it coming in the first place. The code is very simple.

Thanks,
Vikas