#include <stdio.h>
#include <reg51.h>
      const double PI=3.14159;
     double area(double);                 
void main( )

      {
      double r,s; 

	   SCON = 0x50; 
TMOD |= 0x20; 
TH1 = 0xf3; 
TR1 = 1;
TI = 1; 
	  
	                      
      printf( "請(qǐng)輸入半徑：" );
      scanf("%lf",&r);
      s=area(r);                   
     printf("圓的面積是：%lf\n ",s); 
      }

     double area(double r)                      //本函數(shù)計(jì)算圓的面積
	 {
     return (PI*r*r);
}