Bezene Kekule Ring Animation with C BGI graphics in MSDOS

/*
 C code to animate benzene ring
 Sandipan Dey
 BCSE, JU, Kolkata
 2003
*/

#include "stdio.h"
#include "conio.h"
#include "graphics.h"
#include "dos.h"
#include "malloc.h"
#include "math.h"

#define PI 3.14159

void arrow(int x,int y,int sa,int ea,int r,int b1,int b2) {
    int y1,x1;
    arc(x,y,sa,ea,r);
    x1=x+r*cos(PI*ea/180);
    y1=y-r*sin(PI*ea/180);
    line(x1,y1,x1-b1*10,y1);
    line(x1,y1,x1,y1+b2*10);
}

void jumpelectron(int i,int j,int* poly,int c,int x,int y,int z,int w) {
    setcolor(c);
    line(poly[2*i-2]+x,poly[2*i-1]+y,poly[2*j-2]+z,poly[2*j-1]+w);
    setcolor(getmaxcolor());
}

void main() {

    int gd=DETECT,gm,poly[14],size;
    void* bmp1,*bmp2;
    initgraph(&gd,&gm,"");
    poly[0]=poly[1]=100;
    poly[2]=50;poly[3]=150;
    poly[4]=50;poly[5]=221;
    poly[6]=100;poly[7]=271;
    poly[8]=150;poly[9]=221;
    poly[10]=poly[11]=150;
    poly[12]=poly[13]=poly[0];
    drawpoly(7,poly);
    line(60,150,100,110);
    line(60,221,100,261);
    line(140,150,140,221);
    line(100,85,100,100);
    settextstyle(DEFAULT_FONT,HORIZ_DIR,2);
    outtextxy(80,70,":O-H");
    outtextxy(90,50,".");
    outtextxy(98,50,".");
    size=imagesize(85,51,110,65);
    bmp2=malloc(size);
    getimage(85,51,110,65,bmp2);
    outtextxy(250,250,"To Start :Press Ctrl-S");
    while(getch()!=19){fflush(stdin);}

    ellipse(87,79,0,360,7,12);
    size=imagesize(80,67,94,91);
    bmp1=malloc(size);
    getimage(80,67,94,91,bmp1);

    delay(2000);
    arrow(85,87,110,320,12,1,1);
    arrow(35,140,20,270,15,1,-1);
    delay(2000);
    putimage(80,67,bmp1,XOR_PUT);
    putimage(30,140,bmp1,COPY_PUT);
    setcolor(0);
    arrow(85,87,110,320,12,1,1);
    arrow(35,140,20,270,15,1,-1);
    setcolor(getmaxcolor());
    line(105,85,105,100);
    jumpelectron(1,2,poly,0,10,0,0,10);

    delay(2000);
    arrow(30,160,90,340,15,1,1);
    arrow(75,265,120,340,15,1,1);
    delay(2000);
    putimage(30,140,bmp1,XOR_PUT);
    jumpelectron(2,3,poly,getmaxcolor(),10,0,10,0);
    jumpelectron(3,4,poly,0,10,0,0,-10);
    setcolor(0);
    arrow(30,160,90,340,15,1,1);
    arrow(75,265,120,340,15,1,1);
    setcolor(getmaxcolor());
    putimage(82,275,bmp2,COPY_PUT);
    ellipse(100,283,0,360,12,7);
    free(bmp2);
    size=imagesize(300,300,335,325);
    bmp2=malloc(size);
    getimage(300,300,335,325,bmp2);

    delay(2000);
    arrow(120,265,250,60,15,-1,1);
    arrow(170,160,210,150,15,-1,-1);
    delay(2000);
    putimage(82,275,bmp2,COPY_PUT);
    jumpelectron(5,6,poly,0,-10,0,-10,0);
    jumpelectron(4,5,poly,getmaxcolor(),0,-10,-10,0);
    putimage(160,140,bmp1,COPY_PUT);
    setcolor(0);
    arrow(120,265,250,60,15,-1,1);
    arrow(170,160,210,150,15,-1,-1);
    setcolor(getmaxcolor());

    delay(2000);
    arrow(160,125,320,180,20,-1,-1);
    arrow(115,65,260,210,32,1,-1);
    delay(2000);
    putimage(160,140,bmp2,COPY_PUT);
    jumpelectron(6,1,poly,getmaxcolor(),-10,0,0,10);
    settextstyle(DEFAULT_FONT,HORIZ_DIR,2);
    outtextxy(80,70,":");
    setcolor(0);
    line(105,85,105,100);
    arrow(160,125,320,180,20,-1,-1);
    arrow(115,65,260,210,32,1,-1);
    setcolor(getmaxcolor());
    delay(2000);

    jumpelectron(2,3,poly,0,10,0,10,0);
    jumpelectron(4,5,poly,0,0,-10,-10,0);
    jumpelectron(6,1,poly,0,-10,0,0,10);
    ellipse(100,185,0,360,40,55);
    delay(2000);

    free(bmp1);
    free(bmp2);
    getch();
    closegraph();
}