Hello World!
I'm talking about constants in Alice3.
I'm going to write the jumping chicken program using a constant.
I select my variable tile, and I'm going to click the box that says constant.
It's still a double, but the name of a constant is usually all uppercase
and using an underscore to separate words.
So I'm going to name this AMOUNT_TO_JUMP all in uppercase 
and give it an initial value of 0.3 
If you look at our code you see the word final in front of that.
That means that I will not be able to use an assignment statement with AMOUNT_TO_JUMP,
0.3 is its final value and I can't use an assignment statement to change that.
Of  course I could change it in the edit mode by typing custom decimal number 
and typing a new value to that.
But  I cannot use an assignment statement to give it a new value.
It cannot vary or change its value, it is constant.
I'm going to have the chicken move up by AMOUNT_TO_JUMP
and I'm just going to copy that to the clipboard and then drag it back in
Then change this to down.
I can run my program and he goes up and comes back down.
I'm only going to have him jump once because I can't change the value of a constant.