Hello world! I'm talking about creating truth tables. I'm going to use Excel to create it.
We use truth tables for lots of things.
One of the purposes is to look at what our results are going to be.
Another is to make sure that we've used good test data to check every path through the program.

I'm using Excel because I want to be able to sort the results and I can do that easily in Excel.
To start with going to do a rock paper scissors game.
and we have two players we have the computer and me have the user.
and I'm pressing tab go to the next column and put in user.
I'm going to go to the home tab and make that bold.
I misspelled that so let's just double-click and we can edit  it.

Now, in Rock Paper Scissors, the computer could pick any one of those three,
and the user can pick any one of those three.
We multiply three possibilities for the computer times three possibilities for the user,
We have nine possible outcomes.

To start with I'm going to give each of the values for the computer and for the user the value "rock".
Then in this column I'm going to increment to the next value which is paper.
and keep rock the same.
And then this becomes scissors and this stays rock.
at this point I've put in all three values for rock paper scissors,
so what I'm going to do is go back to the first value and increment the value for computer.

The next value here is paper,
and if I type just "s" it'll say scissors.
and keep paper the same,
I put the wrong one in: the next value here is supposed be paper.
And this would be scissors.
This stays paper, and that's the last value did rock paper scissors for rock we get rock paper scissors for paper 
so we go back to the beginning of rock.

I'm going to show you an easy way to do this:
I'm going to pick that and then just drag that down and it filled them in.
so the next value here is going to be scissors,
We're going to copy that by dragging this little handle over here.

Now this is the important column:  this is the result.
This is what I want to display. Let's make that column just a little bit wider.
If they both pick rock I'm going to say "It's a tie."
And if the computer picks rock and the user pics paper, "paper covers rock" so I'm going to put  "You win."
If the user pick scissors and computer picks rock, "Rock smashes scissors",
so the computer wins.
And if the computer picks paper and the user picks rock, "Paper covers rock",
so the computer wins.
This is "It's a tie"
And if the user picks scissors and the computer picks paper, "Scissors cuts paper",
So, "You win."
If the computer picks scissors and the user picks rock, "Rock smashes scissors", "You win."
and "Scissors cuts paper" so the computer wins.
and "It's a tie" if  they both pick the same,

I'm going to select over there and go to data,
and say "Sort",  "My data has headers", 
and I want to sort by the result.
and so this makes it a little easier.

We can see the three conditions where it's a tie;
The three conditions where the user wins, and the three conditions where the computer wins.
and this provides a set of good test data if we run this program and it also lets us simplify it.