OpenGL - Particle Generation

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

#include <ctime>
#include <cstdlib>

#include <iostream>
using namespace std;

#define PARTICLE_SIZE 2000

void grid(){
    int i = 0, j = 0;
    glColor3f(0.89,0.99,0.79);
    glBegin(GL_LINES);
        //hoz line
        for(i=0; i<= 10; i++){
            glVertex2f(-0.1, i/10.0);
            glVertex2f(1.0, i/10.0);
        }
        //verical line
        for(j=0; j<=10; j++){
            glVertex2f(j/10.0, -0.1);
            glVertex2f(j/10.0, 1.0);
        }

        // coordinate line
        glColor3f(0.0,1.0,0.0);
        //hoz line
        glVertex2f(-0.1, 0.0);
        glVertex2f(1.0, 0.0);
        // vertical line
        glVertex2f(0.0, -0.1);
        glVertex2f(0.0, 1.0);


    glEnd();
}

void particle(){
    glPointSize(1.0);
    glColor3f(0.0, 0.0, 0.0);

    glBegin(GL_POINTS);
        srand((unsigned) time(NULL));
        int i=0;
        for(i;i<PARTICLE_SIZE;i++){
            float x = rand()*4.0/100000.00;
            float y = rand()*5.0/100000.00;
            glVertex2f(x, y);
            //cout << x << " " << y << endl;
        }
    glEnd();
}

void init(){
    glClearColor(1.0,1.0,1.0,1.0);
    gluOrtho2D(-0.1,1,-0.1,1.0);
}

void display(){
    glClear(GL_COLOR_BUFFER_BIT);

    particle();
    grid();

    glFlush();
}


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

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);
    glutInitWindowSize(400,300);
    glutInitWindowPosition(200,100);
    glutCreateWindow("Simulation App");

    init();
    glutDisplayFunc(display);
    glutIdleFunc(display);

    glutMainLoop();



    return 0;
}