#include<iostream.h>  // Header file for input-output operations
#include<conio.h>      // Header file for console input/output functions
#include<stdlib.h>     // Standard library for utility functions
#include<graphics.h>   // Header file for graphics functions
#include<dos.h>        // Header file for delay functions

// Function prototype for Bresenham's circle algorithm
void circ_bre(int x,int y,int rad);

// Function prototype for displaying pixels of the circle
void display(int,int,int,int);

void main()
{
    int gd = DETECT, gm, x, y, r;
    initgraph(&gd, &gm, "c:\\tc\\bgi");  // Initialize graphics mode
    cleardevice();  // Clear the graphics screen

    cout << "Bresenham's Circle Generation Algorithm ";
    cout << "\nEnter the center coordinates for the circle: ";
    cin >> x >> y;
    cout << "\nEnter the radius of the circle: ";
    cin >> r;
    
    circ_bre(x, y, r);  // Call function to draw the circle
    getch();  // Wait for user input before closing the graphics window
    closegraph();  // Close graphics mode
}

// Function implementing Bresenham's circle algorithm
void circ_bre(int x, int y, int rad)
{
    float dp;  // Decision parameter
    int x1, y1;
    x1 = 0;  // Initializing x1 and y1 for circle drawing
    y1 = rad;
    dp = 3 - 2 * rad;  // Initial decision parameter

    while (x1 <= y1)
    {
        if (dp <= 0)
            dp += (4 * x1) + 6;  // Update decision parameter if inside the circle
        else
        {
            dp += 4 * (x1 - y1) + 10;  // Update decision parameter if outside the circle
            y1--;  // Move towards the center
        }
        x1++;
        display(x1, y1, x, y);  // Plot the symmetric points
    }
}

// Function to plot symmetric pixels of the circle
void display(int x1, int y1, int x, int y)
{
    putpixel(x1 + x, y1 + y, WHITE);  // Plot points in all 8 octants
    putpixel(x1 + x, y - y1, WHITE);
    putpixel(x - x1, y1 + y, WHITE);
    putpixel(x - x1, y - y1, WHITE);
    putpixel(x + y1, y + x1, WHITE);
    putpixel(x + y1, y - x1, WHITE);
    putpixel(x - y1, y + x1, WHITE);
    putpixel(x - y1, y - x1, WHITE);
}