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OK, so really exciting moment.

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We are getting to the point in our programming journey where our programs are about to get a lot, a

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lot more interesting.

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So why is that?

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Because we are talking about loops and loops are really cool.

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And the first thing that I'm going to introduce you to is the while loop.

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So this will be the first type of loop that we talk about.

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So let's get right into it.

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So let's look at a familiar problem.

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So this is something we've been messing around with.

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It is this password problem where we're just trying to guess the password.

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So a simpler version of this problem is right here.

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We have tackled something that was a little bit even more difficult than this.

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But the thing is, is that this is kind of annoying in general as a problem.

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But the most annoying thing about it is that we have to keep running it over and over and over again,

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right to be able to guess the password again.

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Each of these little password programs we made, you had to basically rerun it, so you could then be

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asked to enter the password again.

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So that's super annoying.

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So what if we can have a program that would just keep asking for us?

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We didn't have to run the program again.

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The program would just keep asking us.

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We'd only have to run it once.

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Well, that is possible, and it's something called a while loop.

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And that's the good news is that we can actually make a program that uses this while loop and does this.

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But I guess the kind of neutral that it neutral is, it's kind of confusing that might be good or bad

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news for you.

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I don't know, but you might not think it's confusing.

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You might think it's confusing.

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Let's see what it's all about.

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So we can use this thing called a wire loop.

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It is a programming construct that keeps repeating whatever you put inside of it until a certain condition

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is false.

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So vice versa, you know, it keeps going.

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As long as the condition is true, it starts when the condition is false.

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So yes, you heard that right?

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I said condition we can use conditions exactly like the ones we've been using in our conditional statements,

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like if else, if and else.

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So just like if, for example, all the stuff that's in the parentheses it evaluates to either true

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or false.

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And if it's true, then we do the stuff in between the curly braces, right?

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While loop is the same thing, except we don't only just do the stuff in the curly braces and move on.

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If this is true in between these parentheses.

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We're going to keep going as long as it's true.

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We're going to keep repeatedly doing the stuff in here, hence the term, while while this stuff in

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here is true.

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Whatever this statement is available, as long as it evaluates to true anything in between the races

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will be Iran.

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And what'll happen is, let's say this is true.

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It runs the stuff in here.

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It gets to the bottom, it comes back up.

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It says, Is this still true?

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Oh, it's still true.

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Yeah, I go do this again and get to the bottom and come back up.

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Is this still true?

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Yes, it is.

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I do this again.

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I go to the bottom, I come back up.

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It just keeps doing that over and over until this thing in here.

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In between the parentheses evaluates to false, in which case it will then move past the close curly

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bracket and continue on with the rest of your code if there are other things in your program.

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So pretty cool.

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Let's go back to this program and see if we can change it up to use a while loop and have it ask us

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multiple times with one run of the program without us having to rerun it all the time, right?

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So I have this pulled up in Visual Studio here.

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Here's that program.

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So let's go ahead and just run it right now.

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I think I've actually compiled it already, so I'm going to go ahead and run it, and I'll just say,

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you know, pass and it's like, try again.

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And it's like, Oh, I was wrong, I got it running again and I'm like, half W. and try again.

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And I ran again.

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And then I say, pass word.

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And you guessed it.

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Well, you know what?

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That's kind of annoying.

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We're going to put a while loop in here and we are going to fix this up.

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So how do we change this to have a while loop?

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Well, we got to think, what is the stuff that we want to happen inside the loop?

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So this stuff, right, repeatedly do stuff in here.

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What is the repeatedly do stuff in here that we want?

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Well, we want to keep asking the user.

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Right.

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So that's one thing, keep asking the user for a password and we want to get that stuff from the user

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when they type it in, right?

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So keep asking the user right here, get stuff from the user.

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Right.

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So pretty simple.

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That's what we want to keep doing.

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So we're going to have these two lines inside of our wow loop.

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So.

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We don't necessarily have to deal with all of this.

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I'm going to go ahead and delete this, and I'm going to get rid of this f right here.

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And what I'm going to do is I'm going to say I'm actually I move this down and I'm going to say while

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and what was this?

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While input is not equal to password, then what's the stuff that we do into this stuff right here?

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I'm going to copy this and paste it in here and dent it.

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This is the stuff that we're going to do.

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It's just going to say into the password.

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So I can also put a little initial check here where I can say.

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You know, into the password, I can like, ask them once and then I can use it, get line.

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To get it and then what I can do is I can just say if

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input not equal to the password, then I'll go ahead and do this while.

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So I didn't that.

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So basically, what's going on is that I asked the user for a password.

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I get that password from them.

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And then I checked to see if they have the right thing.

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And what this really is is it's not just checking to see what's right as the right thing is basically

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based on it being wrong.

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So if it's wrong, if it's not the password, then we go in here and we say while it's wrong.

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Keep asking them for the password.

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So we can actually change this, maybe actually to try again, try again.

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And then we'll keep we'll just keep getting it, and once it's actually correct, so once input is equal

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to password, so this would be false, then it'll basically break out of this wow loop and then it will

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go down here.

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It's already this condition has already been decided, so it hits this.

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And once it's done with this, it just continues on past this curly brace.

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And that means that they would have guessed it right.

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So we can just leave this down here because that means that in fact they did.

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They must have guessed it because otherwise it wouldn't be done with the wow look, right?

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We'd still be in the while loop if they hadn't guessed it yet.

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So let's go ahead and try this out and see how it goes, so I'm going to compile it and I'm going to

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go ahead and run it.

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So enter the password pass, try in your training in the past.

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Well, training in we're training in password, you guessed it.

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Cool, so pretty neat, right?

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So let's continue on learning a bit more about these lives, because there are some strange things that

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can happen due to this nature of how it works with the condition inside here.

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So hop back over to the presentation here.

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So what about this?

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I want you to make a new program that has a main function, and then it just only has this code in here.

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So you're going to tape while true.

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And see out, you can put anything you don't have to say, I'm unstoppable, but is kind of a hint at

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what is going to happen, then go ahead and try running this program and it will be quite interesting

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what you see.

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So go ahead and pass the video and run this.

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And then don't worry, you can play the video again, and I won't tell you how to fix what is probably

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going to happen.

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So if your program went careening out of control without any sign of stopping, you can always do something

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like clicking in the console area and pressing control see, which means holding control and pressing

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and see.

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What this does is it kills the current process that is running and that process is your program.

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So most likely, it's this unstoppable loop program that you've just done right now.

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So as you continue through your program a journey, you will encounter this probably quite often.

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Actually, you'll have these infinite loops and it won't stop and you'll have to control C and then

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you'll have to go debug them and fix them so your program cannot get stuck there in that loop, just

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bouncing from bottom to top.

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So let's take a look at this.

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So I'm going to go ahead, actually, and just do this.

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In case you didn't run that, I'll show you, but you probably already ran it on this field, blah.

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And I'll save it.

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And then we will compile it, and then I will run it.

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And it's just going, look at it blinking and you'll notice as I let it keep running.

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Actually, I don't know if you'll be able to hear it, but my computer fan is starting to get faster.

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The computers just smashing through various lines, printing them out, going crazy.

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So yeah, if you get freaked out.

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Just control C and that will stop it.

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OK, so I'm going to get rid of that.

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And I'm going back here to the presentation, and so we should make a modification to our loop condition

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in our current program because you know what, it kind of almost is like an infinite loop.

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If you make the user, keep having to guess, what if the user can't guess your password?

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I mean, it's probably pretty hard, like they have no idea about any constraints about the password,

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so it can just take them forever and ever and ever and ever.

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And do we really want them to have to look up how to exit out of the program in the terminal?

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They have to like control C.

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That's not that great.

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We probably should have an easier option for our users, right?

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So let's make a modification to this program.

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So I want to go back in here.

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What we should probably do is say that they have an option to quit.

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So what we will say is enter the password or type Q to quit.

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How about that?

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And then what we can do here.

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Is I'll add this in here as well, try again or Typekit Q to quit.

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All we have to do is change our while condition here.

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So what happens is that the input is getting saved over and over again into this variable.

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So when I ran it and I typed pass, it got saved in input.

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You know, then it went up here and it said, is pass equal in the password?

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No, it's not.

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And then so it said, try again.

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And then I entered past W and so passed W over wrote Pass like pass was starting here and now it's passed

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w.

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Then I go back to the top, it says is pass w.

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Not equal to passwords.

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Sorry, last time I said equal, it's really checking if it's not equal to password.

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And it's like, yes, it's true, it's not equal, and then it goes again.

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And I said past W.

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Oh, and that got saved in here, so it keeps overwriting it right?

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If we type Q, Q will get saved into input.

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And then it will say, while Q not equal to password, is CUNA equal to password, well, yeah, IQ

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is not equal to password, so keep going.

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So what we can do is add something to this safe while the input is not equal to password, so it's not

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the right answer.

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And while

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the input is also not equal to the screen Q because we're reading into a string right or reading into

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a string.

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So we want to check.

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We want to loop as long as they haven't got the right answer, which is this.

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And as long as they have not entered a queue because once they've entered queue, we want to stop,

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right, then we're going to once we queue.

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It's going to go back up.

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It's going to say, Oh, input is equal to queue because both sides of the and this is the left side

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of the end.

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This is the right side of the and they both have to be true.

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Both have to be true for this stuff to run, right?

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So if this is false, true and false is false.

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So it will actually stop the well, it'll continue past the F and it will say, you guessed it.

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So let's go ahead and check this theory.

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All right.

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So I run this into the password Typekit account.

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I'm just going to say pass again and then I'm going to say past W. and keep saying, Oh, and then I'm

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going to say, You know what?

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I don't know this.

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I just want to quit.

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I type Q and it just says, you guessed it.

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But did we really guess it?

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No, we didn't use it, right?

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If we quit, we shouldn't be rewarded with guessing it.

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So we should basically say something here that says if input is equal to password, then you can say,

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you guessed it right.

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So and else you can just say whatever you can just say thank you.

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And again, not a semicolon, I cannot tell you right now.

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OK, cool.

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So let's save that unless we run this, OK?

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That is a huge problem.

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And the line could not use template parameter.

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Oh yeah, it's just the Allen in line.

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That's what I was forgetting.

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OK, so we save it and try it again.

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OK, so let's go ahead and run this, so yet this time, if I, you know, I do the same thing and I

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say Pass W. and pass, whoa, and you go, I say to to quit and it's just a thank you, come again.

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And it just might say, you guessed it.

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OK, so that's kind of all I have to say about the wild loops.

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This is going to get really interesting, though, because now we can do a lot more stuff in here and

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that will help us actually solve some pretty cool problems.

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So we will continue on with the wild loops and the next lecture.

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And after we are kind of comfortable with, then we will move on to other types of loops.

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So with that, I'll see you in the next lecture.