一个简单易懂的时钟程序

    /***********简单的时钟程序，界面不是很美观，您可以根据自己的爱好加以修改，如给表盘加上刻度，将指针改为其它形状等*/

    #include<graphics.h>
    #include<math.h>
    #include<dos.h>

    #define PI 3.1415926
    #define x0 320    /*定义钟表中心坐标*/
    #define y0 240

    void DrawClock(int x,int y,int color)   /*画表盘*/
    { int r=150;     /*表盘的半径*/
      float th;
      setcolor(color);
      circle(x,y,r);
      circle(x,y,2);
    }

    void DrawHand(int x,int y,float th,int l,int color)
    {
      int x1,y1;
      x1=x+l*sin(th);
      y1=y-l*cos(th);
      setcolor(color);
      line(x,y,x1,y1);
    }

    void main()
    {int gdriver=DETECT,gmode;
     strUCt time curtime;
     float th_hour,th_min,th_sec;
     initgraph(&gdriver,&gmode,"");

     setbkcolor(0);

     while(! kbhit())
       {
       DrawClock(x0,y0,14);
       gettime(&curtime);   /*得到当前系统时间*/

        gotoxy(35,20);      /*定位输出位置*/
        if((float)curtime.ti_hour<=12)         /*午前的处理*/
           {printf("AM ");
            if((float)curtime.ti_hour<10) printf("0");   /*十点之前在小时数前加零*/
               printf("%.0f:",(float)curtime.ti_hour);
           }
         else         /*午后的处理*/
          {printf("PM ");
           if((float)curtime.ti_hour-12<10) printf("0");
           printf("%.0f:",(float)curtime.ti_hour-12);
          }

         if((float)curtime.ti_min<10) printf("0");
         printf("%.0f:",(float)curtime.ti_min);
         if((float)curtime.ti_sec<10) printf("0");
         printf("%.0f",(float)curtime.ti_sec);

        /*以下三行计算表针转动角度，以竖直向上为起点，顺时针为正*/

       th_sec=(float)curtime.ti_sec*0.1047197551;                  /*2π/60=0.1047197551*/
       th_min=(float)curtime.ti_min*0.1047197551+th_sec/60.0;
       th_hour=(float)curtime.ti_hour*0.523598775+th_min/12.0;      /*  2π/12=0.5235987755   */
       DrawHand(x0,y0,th_hour,70,2);     /*画时针*/
       DrawHand(x0,y0,th_min,110,3);    /*分针*/
       DrawHand(x0,y0,th_sec,140,12);     /*秒针*/

       sleep(1);      /*延时一秒后刷新*/
       cleardevice();
       }

     closegraph();
    }