Checkerboard w/ openGL glRecti - c++

Question

I have a pretty straightforward question. We are asked to make a checkerboard using glRecti in c++ using visual basic 2010. Here's what I have so far and was wondering if anyone can point me in the right direction.
#include <gl/glut.h>
void myInit(void)
{
glClearColor(1.0,1.0,1.0,0.0); // set white background color
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0, 640.0, 0.0, 480.0);
}
void drawChecker(int size)
{
int i = 0;
int j = 0;
for (i = 0; i < 7 ; i++) {
if((i + j)%2 == 0) // if i + j is even
glColor3f( 0.4, 0.2, 0.6);
else
glColor3f( 0.2, 0.3, 0.4);
glRecti(i*size, j*size, size, size); // draw the rectangle
j++;
}
glFlush();
}
void checkerboard(void) {
glClear(GL_COLOR_BUFFER_BIT); // clear the screen
drawChecker(32);
}
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("null"); // open the screen window
glutDisplayFunc(checkerboard); // register redraw function
myInit();
glutMainLoop(); // go into a perpetual loop
}

Answer 1

You should try
for (i = 0; i < 8 ; ++i) {
for (j = 0; j < 8; ++j) {
if((i + j)%2 == 0) // if i + j is even
glColor3f( 0.4, 0.2, 0.6);
else
glColor3f( 0.2, 0.3, 0.4);
glRecti(i*size, j*size, (i+1)*size, (j+1)*size); // draw the rectangle
}
}
You should think if you would rather want to let i and j go to 7 and not to 6, which would make a real checkerboard. Remember that the loop is repeated as long as i is lower than 7 (therefore it is done for i from 0 to 6). Therefore I changed the 7 to 8. If the 7 was really intended, then excuse me for taking this freedom.
Furthermore are the last two arguments not the size of the rectangle, but its opposite vertex, therfore the use of i+1 and j+1.