Example from Getting Started with A Circle class derived from Point

// Borland C++ - (C) Copyright 1991 by Borland International

/* CIRCLE.CPP--Example from Getting Started */

// CIRCLE.CPP A Circle class derived from Point

#include // graphics library declarations
#include "point.h" // Location and Point class declarations
#include // for getch() function

// link with point2.obj and graphics.lib

class Circle : Point { // derived privately from class Point
// and ultimately from class Location
int Radius; // private by default

public:
Circle(int InitX, int InitY, int InitRadius);
void Show(void);
void Hide(void);
void Expand(int ExpandBy);
void MoveTo(int NewX, int NewY);
void Contract(int ContractBy);
};

Circle::Circle(int InitX, int InitY, int InitRadius) : Point(InitX,InitY)
{
Radius = InitRadius;
};

void Circle::Show(void)
{
Visible = true;
circle(X, Y, Radius); // draw the circle
}

void Circle::Hide(void)
{
unsigned int TempColor; // to save current color
TempColor = getcolor(); // set to current color
setcolor(getbkcolor()); // set drawing color to background
Visible = false;
circle(X, Y, Radius); // draw in background color to erase
setcolor(TempColor); // set color back to current color
};

void Circle::Expand(int ExpandBy)
{
Hide(); // erase old circle
Radius += ExpandBy; // expand radius
if (Radius < 0) // avoid negative radius
Radius = 0;
Show(); // draw new circle
};

void Circle::Contract(int ContractBy)
{
Expand(-ContractBy); // redraws with (Radius - ContractBy)
};

void Circle::MoveTo(int NewX, int NewY)
{
Hide(); // erase old circle
X = NewX; // set new location
Y = NewY;
Show(); // draw in new location
};

main() // test the functions
{
// initialize the graphics system
int graphdriver = DETECT, graphmode;
initgraph(&graphdriver, &graphmode, "..\\bgi");

Circle MyCircle(100, 200, 50); // declare a circle object
MyCircle.Show(); // show it
getch(); // wait for keypress
MyCircle.MoveTo(200, 250); // move the circle (tests hide
// and show also)
getch();
MyCircle.Expand(50); // make it bigger
getch();
MyCircle.Contract(75); // make it smaller
getch();
closegraph();
return 0;
}

Example from Getting Started with A Circle class derived from Point, how to code for the graphics, collection of the computer graphics code for BCIS, BE, BIM