OpenGL - Gridding

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

using namespace std;

#define WIDTH 400
#define HEIGHT 300
#define N 10
float dens[N][N] = {};
void init(){
    glClearColor(1.0, 1.0, 1.0,1.0);
    //glMatrixMode(GL_PROJECTION);
    //glLoadIdentity();
    //glOrtho(0, WIDTH, HEIGHT, 0, 0, 1);
    //glMatrixMode(GL_MODELVIEW);
    //gluOrtho2D(0.0,1.0,0.0,1.0);
    //glDisable(GL_DEPTH_TEST);

}



void display(){
    glClear(GL_COLOR_BUFFER_BIT);
    glPointSize(3.0);
    glBegin(GL_QUADS);
    float h = 1.00/N;
    for(int i=0; i<N; i++){
        float x = 1.0*i/N;
        for(int j=0; j<N; j++){
            float y = 1.0*j/N;
            glColor3f(1.0,0.0,0.0);
            glVertex2f(x, y);
            glColor3f(0.0,1.0,0.0);
            glVertex2f(x+h, y);
            glColor3f(0.0,0.0,1.0);
            glVertex2f(x+h, y+h);
            glColor3f(0.0,1.0,1.0);
            glVertex2f(x, y+h);
        }
    }
    glEnd();
    glFlush();
}

int main(int argc, char* argv[]){

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowSize(WIDTH, HEIGHT);
    glutInitWindowPosition(200, 100);
    glutCreateWindow("Lucia OpenGL");

    glClearColor(1.0, 1.0, 1.0, 0.0);
    //glMatrixMode(GL_PROJECTION);
    //glLoadIdentity();
    gluOrtho2D(0.0,1.0,0.0,1.0);
    glutDisplayFunc(display);
    glutMainLoop();

    return 0;
}