OpenGL - Coordinate System

/**

 * This program will draw coordinate system line

 * x line and y line with their corresponding strips

 */

 

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

#define LIMIT 20.0      // limit
#define CENTER (LIMIT - LIMIT - 1)


// prototype
void setup();   // initialization of the program
void display(); // drawing method
void createCoordinate();  // certasian coordinate
void draw();    // draw the object

void createCoordinate(){
    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINES);
        // horizontal lines
        glVertex2f(-LIMIT, 0.0);
        glVertex2f(LIMIT, 0.0);

        // vertical lines
        glVertex2f(0.0, -LIMIT);
        glVertex2f(0.0, LIMIT);
    glEnd();

    // creating strips
    int i=0;
    for(i=0;i<20;i++){
    glColor3f(0.1, 0.0, 1.0);
    glBegin(GL_LINES);
        // horizontal strips
        glVertex2f(i, 0.10);
        glVertex2f(i, -0.10);

        // vertical strips
        glVertex2f(0.10, i);
        glVertex2f(-0.10, i);
    glEnd();
    }
}

// initialization setting
void setup(){
    glClearColor(1.0, 1.0, 1.0, 1.0);
    gluOrtho2D(CENTER, LIMIT, CENTER, LIMIT); // -x1, x2, -y1, y2
}

void display(){
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0, 0.0, 0.0);


    createCoordinate();
    draw();


    glFlush();
}

// drawing area
void draw(){
    // your code here
}


int main(int argc, char *argv[]){
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowPosition(200, 100);
    glutInitWindowSize(400, 300);
    glutCreateWindow("Hello World");
    glutDisplayFunc(display);

    setup();
    glutMainLoop();


    return 0;

}