Simple line drawing in OpenGl

#include <GL/glut.h>         

void display(void)

{

glClear(GL_COLOR_BUFFER_BIT); 

glColor3f(1.0,1.0,0.0);

glBegin(GL_LINES);

glVertex2f(0.5, -0.5);

glVertex2f(-0.5, 0.5);

glEnd();

glFlush(); 

}

void init(){

glClearColor(0.0,0.5,0.2,0.8);

}

int main(int argc, char** argv)

{

glutCreateWindow("simple line"); 

glutDisplayFunc(display);

init();

glutMainLoop();

}