Teach Yourself Sudoku
 Learn the secrets that let you easily solve Sudoku puzzles faster!
 Lesson #2. Understand the Row – Column – Block (RCB) Sudoku structure   On the surface, Sudoku appears to be based on the numbers 1 through 9.  While that’s obviously true, the more important element (in terms of solving Sudoku puzzles), is understanding the Row – Column – Block (RCB) structure inherent in each puzzle.   Lets start with the basics.   Standard Sudoku puzzles consist of a grid composed of 9 rows, 9 columns, and 9 Blocks.  Each of these, in turn, is composed of 9 cells.  Each cell will ultimately hold just one number.   Rows have their 9 cells arranged horizontally.   In any Row, you can only have one occurrence of each of the numbers 1 through 9. In this illustration, Row 8 is highlighted (counting from the top as Row 1.)     Columns have their 9 cells arranged vertically.   In any Column, you can only have one occurrence of each of the numbers 1 through 9. In this illustration, Column 5 is highlighted (counting from the left as Column 1.)     Blocks have their 9 cells arranged in a 3 by 3 grid.   In any Block, you can only have one occurrence of each of the numbers 1 through 9.     Overall, the entire Sudoku grid is 9 x 9 with a total of 81 cells each holding a single number in the range of 1 to 9.   Rows, Columns, and Blocks exist within the overall 81 cell grid.   Any individual cell is simultaneously part of a Row, Column, and Block.  This is a very fundamental but key concept needed to solve Sudoku puzzles.   To see this concept in action, look at the illustrations below. The black box is the individual cell and the shaded gray areas are the associated Row (horizontal), Column (vertical) and Block (3 by 3 area).  Notice how each cell is associated with a unique RCB.          I’ve found that the easiest way to refer to Blocks is simply by their position in the over all grid: Upper Left, Upper Center, Upper Right, Middle Left, Middle Center, Middle Right, Lower Left, Lower Center, and Lower Right..  Check out the illustration below to see these displayed.                                                                         NEXT UP: Lesson #3. What’s POSSIBLES?   Copyright 2006 Gary Ward All Rights Reserved