Program is of the calculator which the usual thing for the operation. It has been totally implemented in the C language with the graphics and mouse functions included in it.
Its not scientific but just a usual one..

\*made by:Ajay Himatsingka
\*email:ajay_krish123@gmail.com*\
#include<graphics.h>
#include<dos.h>
#include"dos.h"
#include"stdio.h"
#include"math.h"
#include<process.h>
#include<conio.h>
union REGS i,o;

char text[35][25]={"7","8","9","*","4","5","6","/","1","2","3","+","0","00",".","-","M","M+","M-","+/-","MR","MC","x^2","sr","OFF","AC","CE","="};

int s=0,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 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(5);
rectangle(x1,y1,x2+2,y2+2);
rectangle(x1,y1,x2+1,y2+1);
setfillstyle(SOLID_FILL,14);
bar(x1,y1,x2,y2);
setcolor(1);
outtextxy(x1+12,y1+7,text);
k++;
}

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

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;
}
/* Move mouse ptr to x,y */
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);
 return(0) ;
}
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);
 return num;
}
allclear()
{
 sq=0;
 accum=0;
 num=0;
 d=0;
 newnum=1;
 printf("%25.5Lf",num);
 return(0);
}
plusminus()
{ if(num!=0)
  {	num*=-1;
	printf("%25.5Lf",num);
  }
  return(0);
}
clearm()
{
m=0;
//printf("%25.5Lf",m);
return(0);
}
decimal()
{
 if(!d)
 {
 d=1;
	if(newnum==1)
	{
	 num=0;
	}
  printf("%25.5Lf",num);
  }
  return(0);
}
square()
{
sq=1;
 num*=num;
 printf("%25.5Lf",num);
return(0);
}
sqroot()
{ sq=1;
 num=pow(num,0.5);
 printf("%25.5Lf",num);
return(0);
}
doublezero()
{
 if(d)
   {
	 d++;
	 d++;
   }
 else
  num*=100;
 printf("%25.5Lf",num);
 return(0);
}
clear()
{
num=0;
printf("%25.5Lf",num);
return(0);
}
void main()
{
int gd=DETECT,gm,x1,x2,y1,y2,i,j,maxx,maxy,x,y,button;
initgraph(&gd,&gm,"g:\\tc\\bgi");
if(initmouse()==0)
 {
  closegraph();
  restorecrtmode();
  printf(" Mouse driver not loded");
  exit(0);
}
setcolor(2);
gotoxy(20,10);
printf("WELCOME TO ISTE");
gotoxy(20,14);
printf("press any key to continue.......");
getch();
cleardevice();
showmouseptr();
movemouseptr(&x,&y);
setcolor(15);
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);
setfillstyle(SOLID_FILL,3);
//bar(200,142,415,161);
outtextxy(50,25,"A Calculator project in C presented by MR.AJAY HIMATSINGKA");
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[s]);
   s++;
   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(0);
	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);   // plus
		break;
	case  15 :
		operation(2);    // minus
		break;
	case  3 :
		operation(3);    // multiplication
		break;
	case  7 :
		operation(4);     // division
		break;
	case 13:
		doublezero();
		break;
	case  14 :
		decimal();
		break;
	case 16:
		m=m;
		printf("%25.5Lf",m); //memory call
		break;
	case 20:
		printf("%25.5Lf",m);
		break;
	case 19:
		plusminus();
		break;
	case 17:
		m=m+num;       //memory plus
		break;
	case 18:
		m=m-num;       //memory minus
		break;
	case 21:
		clearm();
		break;
	case 22 :
		square();
		break;
	case 23:
		sqroot();
		break;
	case 24:
		hidemouseptr();
		setcolor(1);
		cleardevice();
		setcolor(14);
		outtextxy(225,200,"THANK YOU");
		delay(2000);
		exit(0);
		break;
	case 25:
		allclear();
		break;
	case 26:
		clear();
		break;
	case 27:
		num=operation(5);      	 //  equalto
		break;
	 }
	 setcolor(1);
	outtextxy(x1+12,y1+7,text[j*4+i]);
	 }
   }
 x1+=60;

	x2+=60;
}
 }
 }
}

I had to go back to DOS (MS-DOS 6.22) and Borland 4.0 to get it to compile, but it worked well once compiled. On exit, however, it changed my screen colours to white on grey (from white on blue) and left the screen unresponsive to the color command. Great project and a nice looking calculator.