function exit(0) should have a prototype

#include "Stdio.h"
#include "conio.h"
#include "math.h"
#include "graphics.h"
#include <string.h>

   void intgraph();
   void display_cordinate(char bg_color,char line_color);
   int Create_poly(int poly[][2]);
   void fill_poly(int poly[][2],int points,char line_color,char fill_color);
   void Identity(float Matrix[3][3]);
   void Translate_to_Relative(int poly[][2],int points,int Xdis,int Ydis);

   void main()
   {
      int poly[3][2],i,points,Xdis,Ydis;
      float Sx,Sy,Matrix[3][3],temp,Cos,Sin;
      char ch;
      intgraph();

      setfillstyle(8,RED);
      points=Create_poly(poly);
      display_cordinate(DARKGRAY,WHITE);
      fill_poly(poly,points,WHITE,RED);

      getch();
      Identity(Matrix);
      Xdis=0-poly[0][0];
      Ydis=0-poly[0][1];

      Translate_to_Relative(poly,points,Xdis,Ydis);

   Menu:
      restorecrtmode();
      do
      {
     clrscr();
     printf("================================");
     printf("1. Scaling");
     printf("2. Translation");
     printf("3. Rotation");
     printf("4. Reflection [ X axis ]");
     printf("5. Reflection [ Y axis ]");
     printf("6. Reflection [ X=Y axis ]");
     printf("7. Draw ");
     printf("8. EXIT ");
     printf("================================");
     printf("Choose Ur Destiny:- ");
     ch=getche();
      }while((ch<'1')||(ch>'8'));

      switch(ch)
      {
     case '1':
        printf("Enter Scaling Ratio:- ");
        printf("Sx:- ");
        scanf("%f",&Sx);
        printf("     Sy:- ");
        scanf("%f",&Sy);
        for(i=0;i<3;i++)
        {
           Matrix[i][0]=Matrix[i][0]*Sx;
           Matrix[i][1]=Matrix[i][1]*Sy;
        }
        goto Menu;

     case '2':
        printf("Enter Translation [Relative]:- ");
        printf("Tx:- ");
        scanf("%f",&Sx);
        printf("     Ty:- ");
        scanf("%f",&Sy);

        Matrix[2][0]=Matrix[2][0]+Sx;
        Matrix[2][1]=Matrix[2][1]+Sy;

        goto Menu;

     case '3':
        printf("Enter Rotation Angle [Degree]:- ");
        scanf("%f",&Sx);

        Sx=(Sx*3.14)/180;
        Cos=cos(Sx);
        Sin=sin(Sx);
        for(i=0;i<=2;i++)
        {
           temp=Matrix[i][0]*Cos-Matrix[i][1]*Sin;
           Matrix[i][1]=Matrix[i][0]*Sin+Matrix[i][1]*Cos;
           Matrix[i][0]=temp;
        }
        goto Menu;

     case '4':
        Matrix[1][1]=Matrix[1][1]*-1;
        printf("Done");
        getch();

        goto Menu;

     case '5':
        Matrix[0][0]=Matrix[0][0]*-1;
        printf("Done");
        getch();

        goto Menu;

     case '6':
        Matrix[0][1]=1;
        Matrix[1][1]=1;
        printf("Done");
        getch();
        goto Menu;

     case '7':
        for(i=0;i<=points;i++)
        {
           temp=poly[i][0]*Matrix[0][0]+poly[i][1]*Matrix[1][0]+Matrix[2][0];
           poly[i][1]=poly[i][0]*Matrix[0][1]+poly[i][1]*Matrix[1][1]+Matrix[2][1];
           poly[i][0]=temp;
        }

     case '8':
        getch();
//            closegraph();
        exit(0);
      }
      setgraphmode(2);
      display_cordinate(DARKGRAY,WHITE);
      Translate_to_Relative(poly,points,-Xdis,-Ydis);
      fill_poly(poly,points,CYAN,RED);
      getch();
      restorecrtmode();
      do
      {
     clrscr();
     printf("Do you Want to Switch to MENU [Y|N]:- ");
     ch=getche();
      }while( (ch!='Y') && (ch!='N') );
      if(ch=='Y')
      {
     Identity(Matrix);
     Xdis=0-poly[0][0];
     Ydis=0-poly[0][1];

     Translate_to_Relative(poly,points,Xdis,Ydis);
     goto Menu;
      }
      closegraph();
   }

   void intgraph()
   {
      int g=DETECT,d;
      initgraph(&g,&d,"c:\tc\bgi");
   }

   void fill_poly(int poly1[][2],int points,char line_color,char fill_color)
   {
      int pol[20],i;
      char str[2];
      for(i=0;i<=points;i++)
      {
     pol[i*2]=poly1[i][0];
     pol[i*2+1]=poly1[i][1];
      }
      pol[i*2]=poly1[0][0];
      pol[i*2+1]=poly1[0][1];

      setcolor(line_color);
      setfillstyle(8,fill_color);
      fillpoly(points+1,pol);

      setcolor(fill_color);
      settextstyle(1,0,3);
      for(i=0;i<=points;i++)
      {
     sprintf(str,"%c",i+'a');
     outtextxy(poly1[i][0],poly1[i][1],str);
      }
   }

   void Identity(float Matrix[3][3])
   {
      int i,j;
      for(i=0;i<=2;i++)
      {
     for(j=0;j<=2;j++)
     {
        if(i==j)
           Matrix[i][j]=1;
        else
           Matrix[i][j]=0;
     }
      }
   }
   int Create_poly(int poly[][2])
   {
      poly[0][0]=200;
      poly[0][1]=20;

      poly[1][0]=300;
      poly[1][1]=150;

      poly[2][0]=130;
      poly[2][1]=280;

      return 2;
   }

   void display_cordinate(char bg_color,char line_color)
   {
      int i;
      setbkcolor(bg_color);
      setcolor(line_color);
      for(i=0;i<=640;i+=50)
      {
     line(i,0,i,480);
      }

      for(i=0;i<=480;i+=50)
      {
     line(0,i,640,i);
      }
      rectangle(0,0,639,479);
   }

   void Translate_to_Relative(int poly[][2],int points,int Xdis,int Ydis)
   {
      int i;
      for(i=0;i<=points;i++)
      {
     poly[i][0]=poly[i][0]+Xdis;
     poly[i][1]=poly[i][1]+Ydis;
      }
   }