Opengl,C++ : Window-To_Viewport Mapping

To get the display

 #include <GL/glut.h>  
 const int screenWidth = 640;  
 const int screenHeight = 480;      
 // defining the Window  
 void setWindow(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top)  
 {  
      glMatrixMode(GL_PROJECTION);  
      glLoadIdentity();  
      gluOrtho2D(left, right, bottom, top);  
 }  
 // setting the Viewport  
 void setViewport(int left, int right, int bottom, int top)  
 {  
      glViewport(left, bottom, right - left, top - bottom);  
 }  
 void myInit(void)   
 {  
      glClearColor (1.0, 1.0, 1.0, 0.0);  // set black background color  
      glColor3f (1.0f, 0.0f, 0.0f);    // set the drawing color  
 }  
 void drawShape()  
 {       
      glBegin(GL_LINE_LOOP);  
           glVertex2i(150,100);  
           glVertex2i(350, 100);  
           glVertex2i(400, 300);  
           glVertex2i(500, 300);  
           glVertex2i(250,450);  
           glVertex2i(00, 300);  
           glVertex2i(100, 300);  
      glEnd();  
      glFlush();  
 }  
 void myDisplay(void)  
 {  
      glClear(GL_COLOR_BUFFER_BIT);          // clear the screen  
       // set the window  
      int bottomX = 0;  
      int bottomY = 0;  
      int width = 64;  
      int height = 48;  
      int i=0;  
      int j=0;  
      //setViewport( left, right, bottom, top)  
      for(int bottomX=0;bottomX<640;bottomX+=width)  
      {  
           for(int bottomY=0;bottomY<480;bottomY+=height)  
           {  
                setViewport(bottomX, bottomX + width, bottomY, bottomY + height); // set the viewport  
                if((j%2==0 || i%2==1) && (j%2==1 || i%2==0)){  
                setWindow(0.0, 640.0, 0.0, 480.0);   
                drawShape();  
                }  
                else{  
                     setWindow(0.0,640.0, 480.0, 0.0);   
                     drawShape();  
                }  
                     j++;  
           }  
           i++;  
      }  
 }  
 int main(int argc, char** argv)  
 {  
      glutInit(&argc,argv);  
      glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);  
      glutInitWindowSize(screenWidth,screenHeight); //setting the SCREEN WINDOW size  
      glutCreateWindow("Window-To-Viewport Mapping");  
      glutDisplayFunc(myDisplay);  
      myInit();  
      glutMainLoop();  
      return 0;  
 }