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In this video, I'm just going to go 
through some of the basic terminology and 

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rules of Sudoku. 
So this is really kind of like a domain 

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analysis for the problem we're about to 
solve. 

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So first, Sudoku is played on a nine by 
nine board. 

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because it's nine by nine, the board has 
81 of what we're going to call squares. 

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In addition to the 81 squares, we say 
that the board has 9 rows, because it's a 

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nine by nine board, nine columns. 
Cause it's a nine by nine board, and it 

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also has nine boxes, where the boxes are 
little three by three blocks of the whole 

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board. 
And so there's three boxes at the top, 

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three boxes kind of in the middle and 
three boxes at the bottom. 

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So, the rows, the columns and the boxes 
together, comprised what are called 

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units. 
There's 27 total units, because there's 

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nine rows, nine columns, and nine boxes. 
And adding nine, nine and nine gets 27. 

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So there's 27 total units and now we have 
enough terminology to concisely say the 

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goal of the game. 
The goal of the game is to fill every 

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square with a natural number from one to 
nine, but making sure there's not a 

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duplicate number in any unit. 
So there can't be a single row that has a 

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duplicate number in it. 
There can't be a single column that has a 

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duplicate number in it. 
And there can't be a single box that has 

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a duplicate number in it. 
Because we have the term unit we can say 

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that more concisely as there can't be a 
single unit that has a duplicate number 

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in it. 
So just to be clear, this is an illegal 

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move. 
You can't put a six in that third box in 

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the first row, because there's already a 
six in that row. 

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So that's an illegal move. 
Here's another illegal move, you can't 

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put a one there because there's already a 
one in that column. 

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So that's an illegal move. 
And here's another illegal move. 

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You can't put a three there, you can't 
put the red three in because there's 

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already a three in that box. 
That's an illegal move. 

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Again, the goal of the game is to fill in 
every square. 

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Was a natural from one to nine inclusive, 
but making sure that there's not a 

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duplicate number in any unit. 
So that's the quick terminology of Sudoku 

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and a quick summary of the rules. 
Again, if you've never seen Sudoku before 

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and you'd like a bit more detailed 
introduction to the rules of the game. 

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Just do a web search and find one of the 
many Sudoku sites, and you can play one 

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or two quick games before picking up the 
next video.