Beginning Sudoku Cheater Software

I'm planning on making a sudoku cheater program. Before I begin, I should study Sudoku. Sudoku is a board of 81 squares organized in 9 rows of 9 squares each. The typical sudoku board has just enough numbers on it for the player to guess the other numbers on the board. I guess I'm skipping a lot of necessary details. Each row must include numbers 1 through 9 and the same within each column. I play Sudoku sometimes ergo I'm aware of some of the techniques that are used to quickly find missing numbers and I think I may implement these techniques into the code but I've noticed that on the more difficult sudoku games where not many numbers are given or the numbers that are given strategically don't give you any hints as to what the other spaces could be, the trial and error method is required. The program could be entirely based on the trial and error method or I can have a couple functions that go through the most common techniques and then finally a function that looks for the rest of the numbers through trial and error.