Рисование эллипса в центре экрана

#include "stdafx.h"
#include "stdio.h"
#include "stdlib.h"
#include "conio.h"
#include "math.h"
#include "windows.h"
#include "locale.h"
#include "dos.h"
#include "time.h"
#define DX 20
#define DY 20
HDC hDC;
HWND hWnd;
RECT Rect;
HPEN hPen, hOldPen;
HBRUSH hBrush, hOldBrush;
HFONT hFont, hOldFont;
LOGFONT Lf={0};
void clearscreen(int r, int g, int b)
{
    hPen=CreatePen(PS_SOLID, 4, RGB(r,g,b));
    hOldPen=(HPEN)SelectObject(hDC, hPen);
    hBrush=CreateSolidBrush(RGB(r,g,b));
    hOldBrush=(HBRUSH)SelectObject(hDC, hOldBrush);
    Rectangle(hDC, Rect.left, Rect.top, Rect.right, Rect.bottom);
    SelectObject(hDC, hOldPen);
    DeleteObject(hPen);
    SelectObject(hDC, hOldBrush);
    DeleteObject(hBrush);
}
void mashtab(float *mx, float *my)
{
    *my=(Rect.bottom-2*DX)/(10-(-10));
    *mx=(Rect.right-2*DX)/(10-(-10));
}
void osi(float minx, float maxx, float miny, float maxy, float mx, float my, int *osx, int *osy)
{
    if(minx*maxx<0) *osy=fabs(minx)*mx+DX;
    else if(minx>=0) *osy=DX;
    else *osy=Rect.right-DX;
    if(miny*maxy<0) *osx=Rect.bottom-fabs(miny)*my-DY;
    else if(miny>=0) *osx=Rect.bottom-DY;
    else *osx=DY;
    hPen=CreatePen(PS_SOLID, 3, RGB(0,0,0));
    hOldPen=(HPEN)SelectObject(hDC, hPen);
    MoveToEx(hDC, DX, *osx, NULL);
    LineTo(hDC, Rect.right-DX, *osx);
    MoveToEx(hDC, *osy, DY, NULL);
    LineTo(hDC, *osy, Rect.bottom-DY);
    SelectObject(hDC, hOldPen);
    DeleteObject(hPen);
}
void setka(int osx, int osy, float minx, float maxx, float miny, float maxy, float mx, float my)
{
    hPen=CreatePen(PS_DOT, 1 , RGB(255,0,255));
    hOldPen=(HPEN)SelectObject(hDC, hPen);
    Lf.lfHeight=12;
    Lf.lfWeight=900;
    Lf.lfWidth=8;
    CHAR S[20];
    strcpy((char*)Lf.lfFaceName, "Times New Roman");
    hFont=CreateFontIndirect(&Lf);
    hOldFont=(HFONT)SelectObject(hDC, hFont);
    SetTextColor(hDC, RGB(0,0,0));
    SetBkColor(hDC, RGB(255,255,255));
    TextOut(hDC, osy-20, Rect.top+DY-8,(LPCSTR)"Y", 1);
    TextOut(hDC, Rect.right-DX+2, osx-20,(LPCSTR)"X", 1);
    float dx, x, y;
    int xt, yt;
    RECT d;
    dx=(maxx-minx)/10;
    for(x=minx; x<=maxx; x+=dx)
    {
        xt=DX+mx*(x-minx);
        MoveToEx(hDC, xt, Rect.top+DY, NULL);
        LineTo(hDC, xt, Rect.bottom-DY);
        sprintf(S, "%.1f", x);
        TextOut(hDC, xt, osx+8, (LPCSTR)S, strlen(S));
    }
    float dy=(maxy-miny)/10;
    for(y=miny; y<maxy+dy; y+=dy)
    {
        yt=Rect.bottom-my*(y-miny)-DY;
        MoveToEx(hDC, Rect.left+DY,yt, NULL);
        LineTo(hDC, Rect.right+DX, yt);
        sprintf(S, "%.1f", y);
        TextOut(hDC, osy+5, yt, (LPCSTR)S, strlen(S));
    }
        SelectObject(hDC, hOldPen);
        DeleteObject(hPen);
        SelectObject(hDC, hOldFont);
        DeleteObject(hFont);
}
int _tmain(int argc, _TCHAR* argv[])
{
    setlocale(LC_ALL, "Rus");
    SetConsoleCP(1251);
    SetConsoleOutputCP(1251);
    srand(time(0));
    int i, m, k,  r;
    float x, y;
    float maxy, miny, mx, my;
    int osx, osy,;
    float a, b, c, tmp, p, S=0, Smax=0;
    hWnd=GetConsoleWindow();
    MoveWindow(hWnd,0,0,800,800,FALSE);
    SetWindowText(hWnd,(LPCSTR)"krug");
    hDC=GetDC(hWnd);
    GetClientRect(hWnd, &Rect);
    clearscreen(255,255,255);
    mashtab(&mx, &my);
    osi(-10, 10, -10, 10, mx, my, &osx, &osy);
    setka(osx, osy, -10, 10, -10, 10, mx, my);
    printf("radius okr:" );
    scanf("%d%d", &r);
    Ellipse(hDC,250,250,300,300);//Этой функцией должен рисоваться эллипс
    getch();
    ReleaseDC(hWnd, hDC);
    getch();
    return 0;
}