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Hello and welcome to this feat you in this video.

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I'm going to illustrate how the concert keyword work cost is a shot from for constant.

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It's another way you can use to declare variables rather than use the key word you can use konst to

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declare your variables is declared is only a concept.

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Key word should not be re assigned.

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So each time.

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Years of cons key word to create variables they will be variables that you don't expect to reassign.

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So I'm going to show the illustration of this.

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So I've got inside my text editor here.

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I've just added this line of code here so I've created a constant here called birth year and that's

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set down to 1980 and then I got a variable called H.

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And I've said that to 20 17 miners both here which is this constant constant logging the result.

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So inside the console don't lock up passing it the H.

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Which is this variable.

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Now what that would do it would take away this subtract 1980 from 2017 and it all output the result.

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So let me try and save that.

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Let's run run the code inside our text editor and see what happens.

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So just click takes it refresh.

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So you can see here is given me an output of thirty seven.

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So the calculation is working as expected.

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So fine go ahead and see create not a variable.

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So if I come here I create a variable variable.

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We divide key word and I'm going to call it birth year as well.

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Same as a constant

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column.

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I am not going to set base to a different year so I make this.

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19.

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19.

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Oh right.

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So I said that if I run the code again I expect it not to work because I've already got a constant variable

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for that so that should not change.

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So here I am to defining it a game here.

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So let me run and run the code so you can see how that works.

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So fine you can see here get getting errors here because I have reassigned a constant variable so with

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constant variables that you are not supposed to read assigned.

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Alright so I've already got a valley here for berthier and I've created another one here.

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Hence my code is give in an error.

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I'm just going to comment not line out and get rid of that now and save that refresh to code the code

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shoot let memory back refresh.

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You can say is outputting correctly now so we can t key thing to take away.

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Here we use constants to declare your variables.

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They will be the variables.

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You don't expect to change or you don't expect to read a sign.

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Right.

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So that's it.

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Thanks for watching my friend.