This program solves 9x9 Sudoku puzzles. Some puzzles may have multiple solutions, but the software calculates one possible solution. Simply entering a number is enough to start. Copy the numbers to the appropriate locations and click 'Solve Sudoku'. It takes less than a second to get the solution.
If you don't know the rules of Sudoku, you can read them here. You can also practice on the 'Sudoku for Kids' page.
As you progress, you can try the easy, medium, hard, and super versions.