这个为什么会出错？

#include"graphics.h"

#include"stdlib.h"

void main()

{int driver,mode,i,size;

void *buf;

driver=DETECT;

initgraph(&driver,&mode,"");

setbkcolor(BLUE);

cleardevice();

setcolor(LIGHTRED);

setlinestyle(0,0,1);

setlinestyle(1,10);

circle(100,200,12);

floodfill(100,200,12);

size=imagesize(69,169,131,231);

buf=malloc(size);

getimage(69,169,131,231,buf);

putimage(500,169,buf,COPY_PUT);

do

{for(o=0;i<20;i++)

{putimage(70+i,170,buf,COPY_PUT);

putimage(500-i,170,buf,COPY_PUT);

}

for(i=0;i<200;i++)

{putimage(255-i,170,buf,COPY_PUT);

putimage(315+i,170,buf,COPY_PUT);

}

} while(getch()!='q'&&getch()!='Q');

closegraph();

}
这是网上的源

你没有graphics.h这个头文件，下面是graphics.h这个头文件的全部内容，你可以把以下全部内容复制到你自己的头文件里面，也可以在系统包含目录里面增加graphics.h这个文件，把内容复制进去：
/* graphics.h
Definitions for Graphics Package.
Copyright (c) Borland International 1987,1988
All Rights Reserved.
*/
#if __STDC__
#define _Cdecl
#else
#define _Cdecl cdecl
#endif
#if !defined(__GRAPHX_DEF_)
#define __GRAPHX_DEF_
enum graphics_errors { /* graphresult error return codes */
grOk = 0,
grNoInitGraph = -1,
grNotDetected = -2,
grFileNotFound = -3,
grInvalidDriver = -4,
grNoLoadMem = -5,
grNoScanMem = -6,
grNoFloodMem = -7,
grFontNotFound = -8,
grNoFontMem = -9,
grInvalidMode = -10,
grError = -11, /* generic error */
grIOerror = -12,
grInvalidFont = -13,
grInvalidFontNum = -14,
grInvalidVersion = -18
};
enum graphics_drivers { /* define graphics drivers */