Sudoku Rules
It is easy to understand the basic Sudoku rules. All cells of the Sudoku field
shall be filled with numbers (or sometimes letters or symbols) so that every
row, every column, and every area that is hemmed with a thick line (or otherwise
emphasized) contains every possible number exactly once. Most commonly a Sudoku
with a size of 9x9 cells is played. This will be filled with numbers from 1
to 9 and it contains 9 smaller squares of 3x3 cells. To make these rules somewhat
clearer, you will find here examples of numbers that were placed against rules:
On the left, a second 9 was entered into a column that already contained a
9. The picture in the middle shows a 3x3 square with a second 9 and on the
right you find a row that contains more than one 9. These pictures were created
with the MaaTec Sudoku program
using the 'Metal & Metal' board graphic. As you can see, one advantage of playing
Sudokus on a PC is that numbers that
were placed against the rules are immediately marked by the program.
Of course, it would be a bit boring (though not unambitious) to simply fill
empty 9x9 fields. That's why Sudoku puzzles contain some cells with visible
numbers. A good Sudoku will display at least so many numbers that it has only
one possible solution. In this form these puzzles were first published under
the name 'Number Place' by the Dell Magazine in the USA. This idea was then
adopted by the japanese publisher Nikoli who also changed the name of these
puzzles to 'Sudoku'. In this word 'Su' stands for 'number' and 'Doku' for
'single'. It is an abbreviation of the earlier name 'Suuji wa dokushin ni kagiru'
which means something like 'that number is limited only single'. Nikoli still
owns the trademark for the name 'Sudoku' in Japan. So other companies there
use the original name 'Number Place' to publish Sudoku puzzles. Nikoli later
added the rule that the visible numbers need to be arranged in symmetrical
patterns.
