OpenGL draws two points on the screen, a blue point on the right, using anti aliasing technology, and a red point on the left, without anti aliasing technology. Compare the difference between the two

#define GLUT_DISABLE_ATEXIT_HACK
#include<windows.h>
#include <gl/glut.h>
float angle = 0;
// initialization OpenGL
int choose = 1;

void init(void)
{
	glClearColor(1.0f, 1.0f, 0.0f, 0.0f);// Set the background color 
	glShadeModel(GL_SMOOTH);// Set shading , There are two selection modes ：GL_FLAT（ No gradients ） and GL_SMOOTH（ Gradient transition ）
}
// The main drawing process 
void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);// Clear color cache     
	glLoadIdentity();
	glTranslatef(0.0f, 0.0f, -7.0f);      /**<  Move to screen  5 A unit of  */

	if (choose == 1)
	{
	glDisable(GL_BLEND);

    glDisable(GL_POINT_SMOOTH);

    glDisable(GL_POLYGON_SMOOTH);
		glPointSize(30.0);
		glColor3f(1.0f, 0.0f, 0.0f);            /**<  Assign colors  */
		glBegin(GL_POINTS);
		glVertex2f(-1.0, 0.0);
		glEnd();


		glEnable(GL_DEPTH_TEST);
	    glEnable(GL_BLEND);
		glEnable(GL_POINT_SMOOTH);       
			/**<  Enable hybrid  */
		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); /**<  Specify mixing factor  */
		glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);	/**<  behavior control  */
		glPointSize(30.0);
		glColor3f(0.0f, 0.0f, 1.0f);            /**<  Assign colors  */
		glBegin(GL_POINTS);
		glVertex2f(0.0, 0.0);
		glEnd();
	}
	glutSwapBuffers();
}
// Call when the window changes size 
void reshape(int w, int h) {
	glViewport(0, 0, w, h);// Set up the viewport 
	glMatrixMode(GL_PROJECTION);// Set the current projection transformation mode 
	glLoadIdentity();// Replace the current transformation matrix with the identity matrix 
	gluPerspective(45, (float)w / h, 4, 100.0);// Set the orthographic projection body 
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}
void TimerFunction(int value)
{
	angle += 10;
	if (angle == 360)
		angle = 0;


	// Redraw the scene with new coordinates
	glutPostRedisplay();
	glutTimerFunc(500, TimerFunction, 1);
}
// Dealing with keyboards 
void keyboard(unsigned char key, int x, int y) {
	switch (key)
	{
	case 'a':
		choose = 0;
		break;
	case 'b':
		choose = 1;
		break;


	case 27://esc Key to exit 
		exit(0);
		break;
	default:
		break;
	}

	glutPostRedisplay();
}
// Dealing with keyboards 
void specialkeyboard(int key, int x, int y) {
	switch (key)
	{
	case GLUT_KEY_UP:
		choose = 1;
		break;
	case GLUT_KEY_DOWN:
		choose = 0;
		break;


	default:
		break;
	}

	glutPostRedisplay();
}
int main(int argc, char* argv[])	
{
	glutInit(&argc, argv);
	glutInitWindowSize(640, 480);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);

	glutCreateWindow("Basic");// Set the window title 
	init();// initialization OpenGL
	glutDisplayFunc(display);// Set display callback function  
	glutReshapeFunc(reshape);// Set up reshape Callback function 
	glutTimerFunc(500, TimerFunction, 1);

	glutKeyboardFunc(keyboard);// Set the keyboard callback function 
	glutSpecialFunc(specialkeyboard);
	glutMainLoop();// Enter the main loop 

}