The concept of Sudoku is simple. The puzzle consists of a 9x9 square grid that is divided into nine 3x3 squares, resulting in nine rows and nine columns, for a total of 81 small squares. The unsolved Sudoku puzzle supplies only a few numbers in random squares. To solve the puzzle, the remaining squares must be filled in with the numbers 1 through 9, each appearing only once in each row, column and 3x3 square.