#include <GL/gl.h>

void Draw( void ) {
   glClear( GL_COLOR_BUFFER_BIT );
   glColor3f( 0.0f, 0.0f, 1.0f );
   glLineWidth( 1 );
   glBegin( GL_LINES );
   glVertex2f( 0, 0.5f );  
   glVertex2f( 0, -0.5f );  
   glEnd();
   glFlush();  
}

int main( int argc, char *argv[] ) {
   glutInit( &argc, argv );
   glutInitWindowSize( 400, 300 );
   glutInitWindowPosition( 100, 100 );
   glutCreateWindow( "GL Demo" );
   glutDisplayFunc( Draw );
   glClearColor( 0, 0, 0, 0 );
   glutMainLoop();
   return 0;
}
