#include <GL/glut.h>

void display()
{
    glClearColor(1, 1, 1, 0);
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3ub(128, 128, 128);
    glBegin(GL_LINES);
        glVertex2f(-240, 0);
        glVertex2f(240, 0);
    glEnd();
    glutSwapBuffers();
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitWindowPosition(200, 50);
   glutInitWindowSize(480, 360);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
   glutCreateWindow("OpenGL");
        gluOrtho2D(-240, 240, -180, 180);
        glutDisplayFunc(display);
   glutMainLoop();
   return 0;
}