程序代码：

#include <GL/glut.h>
void display()  //定义了所要绘制的图形实体
{
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_POLYGON);
        glVertex2f(-0.5, -0.5);
        glVertex2f(-0.5, 0.5);
        glVertex2f(0.5, -0.5);
        glVertex2f(0.5, 0.5);
    glEnd();
    glFlush();
}

int main(int argc, char ** argv)  //OpenGL的初始化
{
    glutInit(&argc, argv);
    glutCreateWindow("simple");
    glutDisplayFunc(display);
    glutMainLoop();
}