一个画抛物线的程序

/*这是一个画抛物线的程序*/

#include<graphics.h>

#define BKC 9

#define COLOR 8 /* 抛物线颜色*/

#define G 9.856

main()

{int gd=DETECT,gm,p=1,i;

double Vx,Vy,x,y,x1,y1,t;

char ch;

initgraph(&gd,&gm,"");

while(p==1) /*主循环体*/

{

setbkcolor(BKC);

setcolor(14);

setlinestyle(0,0,1);

rectangle(0,0,639,479); /*画边框*/

line(20,460,639,460); /*画横坐标*/

line(20,0,20,460); /*画纵坐标*/

outtextxy(8,467,"0");

setlinestyle(1,0,1);

setcolor(15);

for(i=20;i<640;i+=20)line(i,460,i,0);

for(i=460;i>0;i-=20)line(20,i,640,i);

gotoxy(1,1);

printf("Please Enter Vx:" );

scanf("%lf",&Vx);

printf("Please Enter Vy:");

scanf("%lf",&Vy);

for(t=0.0;;t+=0.00002)

{

x=Vx*t;

y=Vy*t-0.5*G*t*t;

x1=2*x+20; /*画笔定位在用户坐标原点 (20,460) */

y1=460-y*2;

if(y1>460.0x1>640.0) break;

putpixel(x1,y1,COLOR);

}

setcolor(12);

outtextxy(250,8,"Finished! Continue(Y/N)?");

p=-1;

while(p==-1)

{

ch=getch();

if(ch=='y'ch=='Y') { cleardevice();p=1;}

else if(ch=='n'ch=='N') p=0;

else outtextxy(220,200,"ERROR! Please Press 'Y' or 'N'_" );

}

}

closegraph();

}