#include <GL/gl.h>
#include <GL/glut.h>
void display(void)
{
/* clear all pixels */
glClear (GL_COLOR_BUFFER_BIT);
/* draw white polygon (rectangle) with corners at
* (0.25, 0.25, 0.0) and (0.75, 0.75, 0.0)

*/
bool color_change=false;

for(int x=0;x<=400;x+=100)//row maintain
{
    for(int y=0;y<=400;y+=100)//column maintain
    {
        if(color_change)
        {
            glColor3f(1.0,0.75,0.0);
            color_change=!color_change;
        }
        else
        {
            glColor3f(0.0,0.0,0.0);
            color_change=!color_change;

        }
        glBegin(GL_QUADS);
        glVertex2i(x,y);
        glVertex2i(x,y+100);
        glVertex2i(x+100,y+100);
        glVertex2i(x+100,y);
        glEnd();

        glFlush ();

    }
}

//glFlush ();
}
void init (void)
{
/* select clearing (background) color */
glClearColor (0.0, 0.0, 0.0, 0.0);
/* initialize viewing values */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,400.0,0.0,400.0);
}
/*
* Declare initial window size, position, and display mode
* (single buffer and RGBA). Open window with "hello"
* in its title bar. Call initialization routines.
* Register callback function to display graphics.
* Enter main loop and process events.
*/
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
glutInitWindowSize (600, 600);
glutInitWindowPosition (100, 100);
glutCreateWindow ("kl");
init ();
glutDisplayFunc(display);
glutMainLoop();
return 0; /* ISO C requires main to return int. */
}