Chacker board

[Sonia kh]

I have mentioned the code for checker board made on visual studio .I dont know whats the problem with this code .. it just draw only one row of checker board on the drawing window :( help me

//#include <windows.h>   // use as needed for your system
//#include <gl/Gl.h>
#include<stdlib.h>
#include <GL/glut.h>
#include<conio.h>
#include<fstream>
#include<iostream>
int y1=0;
int x1=0;
int x2=0;
int y2=0;


using namespace std;
//<<<<<<<<<<<<<<<<<<<<<<< myInit >>>>>>>>>>>>>>>>>>>>

//void drawPolyLineFile(char * fileName)
//{
//	fstream inStream;//fstream provides an interface to read and write data from files as input/output streams.
//	inStream.open(fileName, ios ::in);	// open the file
//	if(inStream.fail())
//		return;
//	glClear(GL_COLOR_BUFFER_BIT);      // clear the screen 
//	GLint numpolys, numLines, x ,y;
//	inStream >> numpolys;	           // read the number of polylines
//	for(int j = 0; j < numpolys; j++)  // read each polyline
//	{
//		inStream >> numLines;
//		glBegin(GL_LINE_STRIP);	     // draw the next polyline
//		for (int i = 0; i < numLines; i++)
//		{
//			inStream >> x >> y;        // read the next x, y pair
//			glVertex2i(x, y);
//		}
//		glEnd();
//	}
//	
//	inStream.close();
//}

/////////////////////////////////////////////////////
 void myInit(void)
 {
    glClearColor(0.5,0.5,0.5,0.0);			// set white background color
    glColor3f(0.0f, 0.0f, 0.0f);			// set the drawing color 
 	glPointSize(4.0);						// a ‘dot’ is 4 by 4 pixels
	glMatrixMode(GL_PROJECTION); 
	glLoadIdentity();
	gluOrtho2D (0.0, 640.0, 0.0, 480.0);
}
//<<<<<<<<<<<<<<<<<<<<<<<< myDisplay >>>>>>>>>>>>>>>>>
void myDisplay(void)
{
	
	glClearColor(1.0,1.0,1.0,0.0); // white background 
	glClear(GL_COLOR_BUFFER_BIT);  // clear the window
	glColor3f(0.6,0.6,0.6);	
	  // bright gray


	for(int i = 1; i<=8 ; i++)  // read each polyline
	{ 

		glColor3f(0.6,0.6,0.6);
		if(i>1)
	{y1=y1+20;}
		for (int j = 1; j<=8 ; j++)
	{
        if(i%2!=0)
        {
        if(j%2!=0)
        {
        glColor3f(0.6,0.6,0.6);}
        }


         if(i%2!=0)
        {
        if(j%2==0)
        {
        glColor3f(0.0,0.0,0.0);}
        }

          if(i%2==0)
        {
        if(j%2!=0)
        {
        glColor3f(0.0,0.0,0.0);}
        }

            if(i%2==0)
        {
        if(j%2==0)
        {
        glColor3f(0.6,0.6,0.6);}
        }
	
		if (j==1)
		{
				//glColor3f(0.0,0.0,0.0);	
			x1=j*20;
		y1=j*20;
		x2=x1+20;
		y2=y1+20;
		glRecti(x1, y1, x2, y2);
		}
		else
		{//glColor3f(0.6,0.6,0.6);	
		x1=x2;
		y1=y1;
		x2=x2+20;
		y2=y1+20;
		glRecti(x1, y1, x2, y2);}

		/*if(i==2)
		{glClearColor(0.5,0.0,0.0,0.0);}*/

	}	
		
	}
   
		  // dark gray
	
	
	glFlush();
	   // send all output to display 
}



//<<<<<<<<<<<<<<<<<<<<<<<< main >>>>>>>>>>>>>>>>>>>>>>
void main(int argc, char** argv)
{
	glutInit(&argc, argv);          // initialize the toolkit
	glutInitDisplayMode(GLUT_SINGLE |GLUT_RGB); // set display mode
	glutInitWindowSize(640,480);     // set window size
	glutInitWindowPosition(100, 150); // set window position on screen
	glutCreateWindow("Draw Dino"); // open the screen window
	glutDisplayFunc(myDisplay);
	myInit(); 
	glutMainLoop(); 		     // go into a perpetual loop
}

[raptr_dflo]

At line 102, you're resetting y1 in terms of j, regardless of the value of i. You can simplify a great deal of your code by changing where you update values, and noticing something about how the squares alternate:

for (i=1; i<=8; i++) {
  // adjust y2 to match y1
  y2 = y1 + 20;
  // reset x1 before starting row
  x1 = 0;
  for (j=1; j<=8; j++) {
    // adjust x2 to match x1
    x2 = x1 + 20;
    // pick color
    if ((i+j)%2 == 0)
      glColor3f(0.6, 0.6, 0.6);
    else
      glColor3f(0.0, 0.0, 0.0);
    // draw square
    glRecti(x1, y1, x2, y2);
    // update x1 for next square
    x1 = x1 + 20;
  }
  // update y1 for next row
  y1 = y1 + 20;
}

Good luck!