Question about an example

    for (xIdx = 0; xIdx < 36; xIdx++)				// x-direction

		{
			for (yIdx = 0; yIdx < 18; yIdx++)			// y-direction

			{
				// calculate texture coordinates for current quad

				texLeft = float(xIdx) / 35.0f;			// left texture coordinate

				texBottom = float(yIdx) / 18.0f;		// bottom texture coordinate

				texRight = float(xIdx+1) / 35.0f;		// right texture coordinate

				texTop = float(yIdx+1) / 18.0f;			// top texture coordinate