[求助]这是我的程序,为什么后面老报错哦!

/* file: draw a box */

# include <stdio.h>
# include <graphics.h>
# include <genlib.h>

/* constants */

#define h 0.5
#define w 1.0

/* function prototypes */

void drawcrossbox( double x,double y,double width, double height);

/* main program */

main()
{
initgraphics();
drawcrossbox( 0.5,0.5,w,h);
getch();
}

void drawcrossbox( double x,double y,double width,double height)
{
MovePen(x,y);
DrawLine(0,height);
DrawLine(width,0);
DrawLine(0,-height);
DrawLine(-width,0);
}

未定义的符号 '_DrawLine' 在模块 111.txt
未定义的符号 '_MovePen' 在模块 111.txt
未定义的符号 '_initgraphics' 在模块 111.txt

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SF
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