为什么不能打开文件呢？

# include "stdio.h"
# include "math.h"
main()
{
FILE *fp1;
if((fp1=fopen("d:\\ar01.dat", "r"))==NULL);
printf("cannot open the file:ar01.dat\n");
}
我要打开d盘根目录下的文件ar01.dat，居然打不开，郁闷阿