下面是我网上拷贝的程序，自己做了一些修改，运行后发现x，y数值循环随机生成的都一样。请高手帮忙改下！！不慎感激…………
for(i=0;i<num;i++)                                                                     /*随即生成O点坐标*/
      {  
         unsigned int seedVal;
         struct timeb timeBuf;
         ftime(&timeBuf);
         seedVal=((((unsigned int)timeBuf.time&0xFFFF)+
                 (unsigned int)timeBuf.millitm)^
                 (unsigned int)timeBuf.millitm);
         srand((unsigned int)seedVal);
      x1=rand()%500;
      y1=rand()%500;
         x=x1/1000.0;
         y=y1/1000.0;
         printf("x=%lf,y=%lf\n",x,y);

各位高手帮帮忙吧，实在是搞不定了