c언어 (openGL)

#include<GL/glut.h>
void init(void)
{
 glClearColor(1.0, 1.0, 1.0, 0.0);//Set display-window color to white.
 glMatrixMode(GL_PROJECTION);//Set projection parameters
 gluOrtho2D(0.0, 200.0, 0.0, 150.0);
}
void lineSegment(void)
{
 glClear(GL_COLOR_BUFFER_BIT);
 glColor3f(1.0, 0.0, 0.0);
 glBegin(GL_LINES);
 glVertex2i(180, 15);
 glVertex2i(10, 145);
 glEnd();
 glFlush();
}
void main(int argc, char** argv) {
 glutInit(&argc, argv);
 glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
 glutInitWindowPosition(50, 100);
 glutInitWindowSize(400, 300);
 glutCreateWindow("An Example OpenGL Program");
 init();
 glutDisplayFunc(lineSegment);
 glutMainLoop();
}