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So far, we've encountered one type of variable, which is a string.



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Now there's an important word in there and that's called type.



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When you hear people talk about programming languages, you say loosely typed, strongly typed.



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In some cases, no types.



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What they're referring to is the kind of thing that's stored in memory as a variable.



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So to give you a counterexample to the string that we had before it, you can kind of see the remnants



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of here.



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Hello, playground.



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What we're going to do is have a variable number, which is like equal to number eight or something.



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Right.



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So what is that number type?



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Well, it's not a string because it doesn't have the quotes around it.



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It's actually an integer, which is a whole number in everyday language.



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Now, there are some nuances to integers that you need to be aware of, but we'll get into those as



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we move on with the course.



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Let's have a var numb to.



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Equal to and let's give this a decimal seven point eight.



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What kind of number is that?



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Well, it's not an integer because it's not a whole number.



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This is actually a double, which stores a very long sequence of numbers, depending on the processor



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you have in your system, 32 bit or 64 bit.



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But basically it's there to do the complex number calculations.



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Okay.



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And I don't mean complex number in the math sense.



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I mean long numbers to basically what else are we going to have here?



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Let's have our number three and let's explicitly call this something.



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Which is a float now, this is the same thing as a double, we can store decimals in it, but but it



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has a much shorter range so we can store fewer decimals.



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Now, if I was writing a finance app to do High-Speed Trading on the stock market, I would never use



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a float.



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I would use the most accurate number because the rounding errors that come from floats will destroy



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your application and give you totally incorrect output rates.



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That would be an error, obviously.



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Now, if you want to know what type of things these are, we can actually call something that's called



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type.



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Here it is on the second line type of.



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And if you just pass in.



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Let's say numb, and then we run all of this.



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You're going to see this is the integer type.



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Right.



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And of course, we can do the same with number two.



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And the same with number three.



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OK, so we have an inch, we have a double and we have a float, so we can always check the types.



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Of course, like I said before, sometimes it's better to make it explicit what you want.



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So if I was making a financial map, everything would be a double in the highest, what you call it



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certainty.



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That's not the word I'm looking for.



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What's the word?



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I'm looking for people.



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The highest accuracy.



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That's it.



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Highest accuracy type of number.



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Right.



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So what's next?



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Ah, here we go.



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Now in iOS and Mac in general, every integer is actually referred to as a unit, which I think stands



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for Universal Integer.



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I could be wrong about that.



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If we take a ONT eight that is actually stored in eight bytes, I believe, or eight bits, one of the



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other, and if we look at the Macs and then press play on that.



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The UNT max is two five five, so that can store from zero to two, five four or two, five five I believe.



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I think it's two five five.



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If you put a negative sign in front of it when you declare it, then you can store from like minus one



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to seven to plus one to seven.



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It's a bit of a weird one we will never use under eight.



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OK, there is no need to do it in a modern application.



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If you're making stuff on a microcontroller like an Arduino, then a untracked is your friend because



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it uses much less memory.



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Just make sure that you're never going to exceed the two five five four what you need it for.



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Now, you can imagine there are all kinds of us, such as 16 dot Macs.



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We have the U.S., 32 dot max and of course ont 64 dot Macs.



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And if we play all of these, we'll see what their maximum values are.



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So sixteen is sixty five thousand.



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You may remember that if you had really old computers and if you're young and watching this, you won't



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know this at all.



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I'm guessing we used to have screens with sixteen bit color, which was amazing because you could have



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65000 colors these days.



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You can have millions of colors.



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Right.



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But that's the state of the art.



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Back then.



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We also before that had eight bit screens which had 255 colors.



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So, you know, there's really old graphics, you see.



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Well, that's the root of it.



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It's stored an integer that was eight bits or bytes.



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It's probably bits, but anyway.



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32 bit stores that many numbers and 64 bit stores that many.



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So if I was making a financial map, I would make sure I was running on a 64 bit system.



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Every system these days is capable of 64 bit, but.



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If you run on a 32 bit, that could potentially be a rounding error for a you integer or the bit where



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it falls off the end and your whole program crashes.



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OK, so you always got to bear in mind with variables, there are limits to what they can store, what



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they can do and various other properties that they have.



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OK, now, of course, we can define integers the explicit way.



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So if I was going to do my num up top, I could say, hey, let's make this a U.



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Int eight, because it actually fits in that.



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But if I changed that to eight hundred, look what happens.



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Integer, literal, eight hundred overflows.



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So you've come to the very first error that you need to know about, which is called an overflow error.



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It basically means you've gone out of range of what can actually be stored inside that variable.



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You've heard of the website Stack Overflow.



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That's based on two errors, the stack trace where you can trace through what went wrong and the overflow



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which you've just seen.



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Hence the name stack overflow.



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Right.



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Let's give you a little bit of homework, so let's copy this over.



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And let's paste it straight in here.



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Create an integer of any value in two ways, one explicitly typed and one implicitly typed.



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Good luck.