Calculator program in C language using graphics

Calculator program in C:

#include<stdio.h>
#include<graphics.h>
#include<dos.h>
#include<math.h>
union REGS i,o;
char *text[]={ "7","8","9","*",
	   "4","5","6","/",
	   "1","2","3","+",
	   "0","00",".","-",
	  "M","M+","M-","+/-",
	  "MR","MC","x^2","sr",
	  "OFF","AC","CE","="};

int k=0,pass,op,prop,newnum=1,bt,memo=1,d=0,sq;
long double num=0,accum,m;

void normalbutton(int ,int ,int ,int,char**);

void main()
{
int gd=DETECT,gm,x1,x2,y1,y2,i,j,maxx,maxy,x,y,button;
char *text1[]={"","p","r","o","g","r","a","m"," ","b","y",":",
	 "W","e","b","e","d","u","c","l","i","c","k"};

initgraph(&gd, &gm, "C:\\TC\\BGI");

if(initmouse()==0)
 {
  closegraph();
  restorecrtmode();
  printf("Mouse driver not loded");
  exit(1);
  }
  showmouseptr();
  movemouseptr(&x,&y);

setbkcolor(11);
setcolor(1);
rectangle(198,140,417,163);
rectangle(199,141,418,164);
rectangle(197,139,416,162);
rectangle(185,130,430,450);
rectangle(184,129,431,451);
rectangle(182,127,433,454);
rectangle(181,126,434,453);

outtextxy(200,50,"*** Welcome to Webeduclick Calculator ***");
outtextxy(200,100,"Press OFF button to exit....");
y1=140;
y2=160;

	for(j=0;j<7;j++)
 {
  x1=200;
  x2=235;
  y1+=40;
  y2+=40;

   for(i=0;i<4;i++)
  {
   normalbutton(x1,x2,y1,y2,text);
   x1+=60;
   x2+=60;
   }
 }
while(1)
  {
	getmousepos(&button,&x,&y);
	y1=140;
	y2=160;

  for(j=0;j<7;j++)
 {
  x1=200;
  x2=235;
  y1+=40;
  y2+=40;

   for(i=0;i<4;i++)
  {

	 if((x<x2&&x>x1)&&(y<y2&&y>y1))
   {
	if((button & 1)==1)
	 {  gotoxy(28,10);
	bt=j*4+i;
	setcolor(11);
	outtextxy(x1+12,y1+7,text[j*4+i]);

	if(num>pow(10.0,18))
	exit();
	delay(10);
	delay(250);
	delay(10);
	 switch (bt)
	 {
	 case  8 :
	   addnum(1);
	   break;
	 case  9 :
	   addnum(2);
	   break;
	 case  10 :
	   addnum(3);
	   break;
	 case  4 :
	   addnum(4);
	   break;
	 case  5 :
	   addnum(5);
	   break;
	 case  6 :
	   addnum(6);
	   break;
	 case  0 :
	   addnum(7);
	   break;
	 case  1 :
	   addnum(8);
	   break;
	 case  2 :
	   addnum(9);
	   break;
	 case  12 :
	   addnum(0);
	   break;
	 case  11 :
	   operation(1);
	   break;
	 case  15 :
	   operation(2);
	   break;
	 case  3 : 
	   operation(3);
	   break;
	 case  7 :
	   operation(4);
	   break;
	 case 13:
	   doublezero();
	   break;
	 case  14 :
	   decimal();
	   break;
	 case 16:
	   mem();
	   break;
	 case 20:
	   recallmem();
	   break;
	 case 19:
	   plusminus();
	   break;
	 case 17:
	   plusm();
	   break;
	 case 18:
	   minusm();
	   break;
	 case 21:
	   clearm();
	   break;
	 case 22 :
	   square();
	   break;
	 case 23:

	   sqroot();
	   break;
	 case 24:

	   hidemouseptr();
	   setcolor(1);
	   for(j=0;j<20;j++)
	 {
	for(i=75;i<481;i+=20)

	   line(0,0+i+j,640,j+0+i);

	   delay(100);
	 }
	   setcolor(14);
	   outtextxy(225,200,"Thanks for using Webeduclick Calculator !");
	   delay(2000);
	   setcolor(13);
	for(j=0;j<20;j++)
	 {
	for(i=0;i<640;i+=20)

	   line(0+i+j,0,j+0+i,640);

	   delay(100);
	 }
	   setcolor(1);

	   for(i=0;i<25;i++)
	  {
	outtextxy(75+10*i,200,text1[i]);
	   delay(50);
	  }
	   for(i=0;i<29;i++)
	  {
	   delay(50);
	  }

	   delay(2500);
	   delay(10);
	   exit();
	   break;
	 case 25:
	  allclear();
	  break;

	 case 26:
	  clear();
	  break;

	 case 27:

	   operation(5);
	   break;
	 }
	 setcolor(1);
	outtextxy(x1+12,y1+7,text[j*4+i]);

	 }
   }
	x1+=60;
	x2+=60;

   }

 }

  }

}

void normalbutton(int x1,int x2,int y1,int y2,char **text)
{
setcolor(15);
rectangle(x1-2,y1-2,x2+1,y2+1);
rectangle(x1-1,y1-1,x2+2,y2+2);
setcolor(7);
rectangle(x1,y1,x2+2,y2+2);
rectangle(x1,y1,x2+1,y2+1);

setfillstyle(SOLID_FILL,2);
bar(x1,y1,x2,y2);
setcolor(1);
outtextxy(x1+12,y1+7,text[k]);
k++;
}

initmouse()
{
 i.x.ax=0;
 int86 (0x33,&i,&o);
 return(o.x.ax);
}
hidemouseptr()
{
	 i.x.ax=2;
	 int86(0x33,&i,&o);
}

showmouseptr()
{
 i.x.ax=1;
 int86(0x33,&i,&o);
 return 0;
}

getmousepos(int *button,int *x,int *y)
{
 i.x.ax=3;
 int86(0x33,&i,&o);
 *button=o.x.bx;
 *x=o.x.cx;
 *y=o.x.dx;
 return 0;
}

movemouseptr(int *x,int *y)
{
 i.x.ax=4;
 int86(0x33,&i,&o);
 o.x.cx=*x;
 o.x.dx=*y;
 return 0;
}

addnum(int pass)
{   if(sq)
	newnum=1;

	if(newnum)
	  {      if(d)
	{
	  num=pass/(pow(10.0,d));
	  d++;
	  newnum=0;
	}
	 else
	{  num=pass;
	   newnum=0;
	}
	  }
	else
	{
	   {    if(d)
	{
	   if(num<0)
	 num=num-pass/(pow(10.0,d));
	   else
	 num=num+pass/(pow(10.0,d));
	  d++;
	}
	else
	{
	num=num*10+pass;
	}
	}
	 }
 printf("%25.5Lf",num);
}

operation(int opr)
{  long double pnum;
   pnum=num;

   if(newnum && (prop != 5) && memo)
   {
   }
   else
  {  newnum=1;
	 d=0;
	 sq=0;
	 switch(prop)
	{
	 case 1:
	accum=accum+pnum;
	break;
	 case 2:
	accum=accum-pnum;
	break;
	 case 3:
	accum=accum*pnum;
	break;
	 case 4:
	accum=accum/pnum;
	break;
	 default:
	   accum=pnum;
	 }
  }
	prop=opr;
	num=accum;
 printf("%25.5Lf",num);
}

allclear()
{
 sq=0;
 accum=0;
 num=0;
 d=0;
 newnum=1;
 printf("%25.5Lf",num);
}

mem()
{
 m=num;
}
recallmem()
{
 memo=0;
 printf("%25.5Lf",m);
 num=m;
}
plusminus()
{ if(num!=0)
  {	num*=-1;
	printf("%25.5Lf",num);
  }
}


plusm()
{
m+=num;
}
minusm()
{
m-=num;
}
clearm()
{
m=0;
}
decimal()
{
 if(!d)
  {d=1;
	if(newnum==1)
	{
	 num=0;
	}
  printf("%25.5Lf",num);
  }
}

square()
{ sq=1;
 num*=num;
 printf("%25.5Lf",num);

}
sqroot()
{ sq=1;
 num=pow(num,0.5);
 printf("%25.5Lf",num);

}
doublezero()
{
 if(d)
   {
	
	 d++;
	 d++;
   }
 else
  num*=100;
 printf("%25.5Lf",num);
}
clear()
{
num=0;
printf("%25.5Lf",num);
}

Output: