MidpointCircle

#include <stdio.h>
#include <graphics.h>
void MidpointCircle( int x0, int y0, int R );

int main()
{
	int	x0, y0;
	int	R;
	int	driver = DETECT, mode;
	initgraph( &driver, &mode, "C:\\tc20" );
	printf( "Input x0,y0:" );
	scanf( "%d,%d", &x0, &y0 );
	printf( "Input radius:" );
	scanf( "%d", &R );
	MidpointCircle( x0, y0, R );
	getch();
	closegraph();
	return(0);
}

void MidpointCircle( int x0, int y0, int R )
{
	int	x[8], y[8];
	int	deltax, deltay, d;
	int	color[8] = { BLUE, GREEN, RED, YELLOW, WHITE, BROWN, CYAN, MAGENTA };
	int	i;
	d	= 1 - R;
	deltax	= 3;
	deltay	= 5 - R - R;
	x[0]	= x0; y[0] = y0 + R;
	x[4]	= x0 + x0 - x[0]; y[4] = y0 + y0 - y[0];
	x[3]	= x[0]; y[3] = y[4];
	x[7]	= x[4]; y[7] = y[0];
	x[1]	= y[0] + x0 - y0; y[1] = x[0] - x0 + y0;
	x[5]	= x0 + x0 - x[1]; y[5] = y0 + y0 - y[1];
	x[2]	= x[1]; y[2] = y[5];
	x[6]	= x[5]; y[6] = y[1];
	while ( x[0] <= y[0] )
	{
		for ( i = 0; i < 8; i++ )
			putpixel( x, y, color );
		if ( d < 0 )
		{
			d	+= deltax;
			deltax	+= 2;
			x[0]++; y[1]++;
			y[2]--; x[3]++;
			x[4]--; y[5]--;
			y[6]++; x[7]--;
		}else  {
			d	+= deltax + deltay;
			deltax	+= 2;
			deltay	+= 2;
			x[0]++; y[0]--;
			x[1]--; y[1]++;
			x[2]--; y[2]--;
			x[3]++; y[3]++;
			x[4]--; y[4]++;
			x[5]++; y[5]--;
			x[6]++; y[6]++;
			x[7]--; y[7]--;
		}
	}
}

// other one:
#include <stdio.h>
#include <graphics.h>
void MidpointCircle( int x0, int y0, int R );

int main()
{
    int    x0, y0;
    int    R;
    int    driver = DETECT, mode;
    initgraph( &driver, &mode, "C:\\tc20" );
    printf( "Input x0,y0:" );
    scanf( "%d,%d", &x0, &y0 );
    printf( "Input radius:" );
    scanf( "%d", &R );
    MidpointCircle( x0, y0, R );
    getch();
    closegraph();
    return(0);
}

void MidpointCircle( int x0, int y0, int R )
{
    int x, y, deltax, deltay, d;
    x    = 0; y = R; d = 1 - R;
    deltax    = 3;
    deltay    = 5 - R - R;
    while ( x <= y )
    {
        putpixel( x + x0, y + y0, 1 );
        putpixel( y + x0, x + y0, 2 );
        putpixel( y + x0, -x + y0, 3 );
        putpixel( x + x0, -y + y0, 4 );
        putpixel( -x + x0, -y + y0, 5 );
        putpixel( -y + x0, -x + y0, 6 );
        putpixel( -y + x0, x + y0, 7 );
        putpixel( -x + x0, y + y0, 8 );
        if ( d < 0 )
        {
            d    += deltax;
            deltax    += 2;
            x++;
        }else  {
            d    += deltax + deltay;
            deltax    += 2;
            deltay    += 2;
            x++; y--;
        }
    }
}