Thread: C++ help!

I want to add the gravity factor in my program.I have a circle class and I want to move the circle under gravity.I used opengl library to make the circle but dont know how to open it as if it falling!

Please help me!

Code:

#include "glut.h"
#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <iostream>
using namespace std;

#define M_PI 3.14159265358979323846f

int g_Width=400;
int g_Height=400;
float gravity=200;
int Mx=0;
int My=0;
char press;

void init();
void myMouseFunction( int button, int state, int mouseX, int mouseY );
void myKeyboardFunction( unsigned char key, int mouseX, int mouseY );
void mySpecialKeysFunction(int key, int x, int y);
void myReshapeFunction( int width, int height );
void myTimerFunction( int val );
void myDisplayFunction();
void myMouseMoveFunction(int x,int y);

class Circle{

    int x;
    int y;
    int radius;
public:

    Circle(){};
    ~Circle(){ printf("destructor called\n");}
    
    static int count;

    Circle(int a, int b, int c)
    {
        x=a; y=b; radius=c;
    }
    void set_data(int a, int b, int c)
    {
        x=a; y=b; radius=c;
    }
    
    void draw_circle()
    {
        float angle;
        count++;
   
    glColor3f(0.0f, 1.0f, 0.0f);
    glLineWidth(1.0f);
    glBegin(GL_LINE_LOOP);
    {
    
    for(int i = 0; i < 100; i++) {
        
        angle = i*2*M_PI/100;
        glVertex2f(x + (cos(angle) * radius), y + (sin(angle) * (radius)));
    

    }}
    glEnd();
   
    }

    friend void display_circle_data(Circle c); //Friend Function
    

};
int Circle::count=0;

//friend function
void display_circle_data(Circle c){
    printf("\nRadius is %d\n",c.radius);
    printf("Xvalue is %d\n",c.x);
    printf("Yvalue is %d\n",c.y);
}

Circle x(0,0,5);
Circle y(399,399,5);
Circle z(x);

Circle* c5 = new Circle();


int main(int argc, char** argv)
{
    glutInit( &argc, argv );

    glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA );
    glutInitWindowSize( g_Width, g_Height ); 
    glutInitWindowPosition( 0, 0 );
    glutCreateWindow( "Danish game wala" );

    init();

    glutMouseFunc( myMouseFunction );
    glutKeyboardFunc( myKeyboardFunction );
    glutSpecialFunc( mySpecialKeysFunction );
    glutMotionFunc(myMouseMoveFunction);

    glutReshapeFunc( myReshapeFunction );
    glutDisplayFunc( myDisplayFunction ); 
    glutTimerFunc( 33, myTimerFunction, 0 );     
    //glutFullScreen();
    //glutSetCursor( GLUT_CURSOR_NONE );

    

    glutMainLoop();
    

    return 0;
    
         
    

}

void init(void) 
{
    glClearColor( 0.0, 0.0, 0.0, 0.0 );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();

    glOrtho(0.0, g_Width, 0.0, g_Height, -1.0, 1.0);
}

void myMouseFunction( int button, int state, int mouseX, int mouseY ) 
{
    //glVertex2f(mouseX,mouseY);
    printf("\nmouseX: %d mouseY: %d, State: %d",mouseX,mouseY,state);
    Mx=mouseX; My=mouseY;

    
    cout<<"C is pressed\n";

    c5->set_data(mouseX,400-mouseY,5);
    //for (int gravity=0;gravity<100;gravity++){
    c5->draw_circle();
    //glClearColor(0.0f, 0.0f, 0.0f, 1.0f );
    //glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//    }
    if (state==1){
    cout<<"No of Circles are "<<(Circle::count)/2;
    }
    
    
        
     if(press =='d'){
        cout<<"delete";
        //delete c5;
        
    }
    else if(press =='s'){
        
        }
    if(press =='t'){
        }
    
    //xCircle s(mouseX,400-mouseY,5);
}

void myKeyboardFunction( unsigned char key, int mouseX, int mouseY )
{
    if( key == 'c' ) // i.e. Esc key
    {
        press ='c';
        //display_circle_data(s);
    }
    if (key=='d')
    {press='d';
        }
    else if (key=='s')
    {press='s';
    }
    if (key=='t')
    {press='t';
    }
    if (key=='+')
    {
    }
    if (key=='-')
    {
    }
    else if(key==27)
        exit(0);
}

void mySpecialKeysFunction(int key, int x, int y)
{
    switch( key )
    {
    case GLUT_KEY_UP:
        break;
    case GLUT_KEY_DOWN:
        break;
    case GLUT_KEY_LEFT:
        break;
    case GLUT_KEY_RIGHT:
        break;
    case GLUT_KEY_HOME:
        break;
    case GLUT_KEY_END:
        break;
    case GLUT_KEY_PAGE_UP:
        break;
    case GLUT_KEY_PAGE_DOWN:
        break;
    }
}

void myReshapeFunction( int width, int height )
{
    glClear(GL_COLOR_BUFFER_BIT);

    g_Width  = width; 
    g_Height = height;

    glViewport (0, 0, g_Width, g_Height);

    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    glOrtho(0.0, g_Width, 0.0, g_Height, -1.0, 1.0);
}

void myTimerFunction( int val )
{
    glutTimerFunc( 33, myTimerFunction, 0 );     
    myDisplayFunction();
}
int i=0;
void myDisplayFunction()
{
//    glClearColor(0.0f, 0.0f, 0.0f, 1.0f );
//glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    
    
    
    //x.draw_circle();
    //y.draw_circle();
    //s.draw_circle();
    glutSwapBuffers();
    
}

void myMouseMoveFunction(int x,int y)
{
    printf("Mouse moved at x:%d y:%d",x,y);
}