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Now there are three numbering systems that use a network engineer need to know you need to know decimal
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binary and hexadecimal decimal is what's called a base 10 numbering system.
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There are 10 numbers 0 up to 9.
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I'm pretty sure you're very familiar with this numbering system.
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So a number like 128 or 255 is an example of a decimal number.
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We have binary which is a base to numbering system there are two numbers either 0 or 1.
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I've discussed binary in a separate video so if you're not sure about binary please make sure that you
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look at that video as an example 128 in binary would be this.
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So one followed by eight zeros 255 would be eight ones in binary.
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Those are examples of binary numbers based to numbering system only two numbers.
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So in other words they have fewer numbers than base 10 or decimal.
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Here we have 10 numbers here we have two numbers hexadecimal has 60 numbers so it has more numbers than
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decimal we have numbers 0 all the way to 9 similar to decimal BUT THEN WE HAVE A B C D E and F.
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So once again we have three numbering system here.
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We've got decimal which has 10 numbers binary which has two numbers hexadecimal which has 16 numbers
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hexadecimal.
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Isn't that complicated.
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You just have more numbers that you can work with.
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I'm going to compare hexadecimal to decimal now to make it easier to understand the equivalent decimal
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number for hexadecimal 0 is zero notice.
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0 2 9 is the same as Decimal.
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So if I gave you a decimal number of eight in hexadecimal it's also eight.
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Compare that to binary in binary that would look like this one would look like this in binary.
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So that's the binary prevalent but it's 1 in hexadecimal.
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This is where it gets different but all you need to remember is the following rule.
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The hexadecimal equivalent for decimal 10 is a four decimal eleven is B decimal twelve is c thirteen
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is d fourteen is e fifteen is f remember that these additional numbers equate to these numbers in decimal
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in hex we have numbers once again zero to nine and then we have a two F..
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Now I've just put them into two separate groupings share.
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They're not really separated.
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They're all part of hexadecimal.
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I've just done that to show you what's similar to decimal and what's a little bit different to decimal
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hexadecimal values or from zero to 15 decimal zero to 15 or hexadecimal 0 to F.
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So here's a comparison showing hexadecimal binary and decimal 9.
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Looks like that 5 looks like that.
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Notice this is exactly the same as decimal once again binary values looked like that and then you just
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need to remember that ten eleven twelve thirteen fourteen fifteen is represented by numbers a b c d
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e and f notice the biggest number in hexadecimal is 15 and that's what it looks like in binary.
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So if I gave you a binary number like 1 1 0 0 the easiest way to work this out is just say what is that
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in decimal decimal that equates to a 1 decimal that equates to 2 decimal that equates to 4 and that
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equates to an 8.
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We haven't got these two but set on so it's eight plus four which is 12 which is C in hexadecimal.
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Once again if you're not sure about how to do binary two decimal or decimal two binary conversions have
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a look at the video where I discuss binary.
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Let's look at some more complicated examples such as 128 128 looks like this in binary.
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Now I've split it on purpose into two groupings of four bits.
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Why.
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Because going back here remember that the biggest number in hexadecimal is F which equates to for binary
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ones smallest number is zero which equates to for binary zeros.
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So if we take a 128 and we write it like that but we split it into groupings of four.
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But each verse equates to eight in decimal.
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This equates to zero in decimal which equals 80 in hexadecimal.
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Now it's important that you know how to work this stuff out but in the real world you'd obviously use
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a calculator so you can use a calculator to verify your answers.
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So are we using a ten base system or a 16 based system.
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Let's use 16 and specify zero.
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Remember a 16.
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That numbering system means hexadecimal base sixteen so eight is zero in hexadecimal equals 128 in decimal
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hundred twenty eight in decimal is eight zero in hexadecimal.
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And if we look at the binary it's one followed by seven zeros.
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Okay.
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What about 255 255.
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Looks like this in binary it's eight binary ones.
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If we split that in half that equals 15.
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And that equals 15.
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I'll just write it out here.
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That equals decimal 15.
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Why.
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Because that's one that's two that's four and that's eight eight plus four plus two plus one is 15 15
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in decimal equals F in hexadecimal.
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Going back to our table here that is that in decimal which equals that in hexadecimal.
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So the easiest way to work this out is to take a decimal number put it into binary.
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Break it in two groupings of four.
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Let's convert those four that's into a decimal number and that'll give you your hexadecimal number.
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So that equals f f.
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Here's another example two to four that's a decimal number.
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Convert that into binary.
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It looks like this.
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Why.
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Because that is 128 that is 64 and that is 32 128 plus 64 plus 32 equals two to four.
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So that if you split it into two groupings of four bits that is decimal zero.
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And if you look at the first four bits in decimal.
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That would be let's rewrite each year.
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So it's not confusing.
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That would be a one that would be a two.
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That would be a four and that would be an eight.
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We're not going to use one here because the binary but is set to zero.
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So it's eight plus four plus two which is 14.
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And if we go back to our table 14 in decimal is e in hexadecimal we can say it looks like that in binary
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once again.
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So that is an E.
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So this would be e zero as we can see over there.
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Okay one more example.
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So two forty two forty in binary looks like this.
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Why.
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Because 128 plus 64 plus 32 plus 16 equals 240.
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Forgive my bad handwriting.
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You split this in half.
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So this is easy.
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That equals zero in decimal.
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Here we've got four binary ones which hopefully you remember is f just going back for binary ones is
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15 or F in hexadecimal.
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So answer is F zero to 40 in hexadecimal is F zero.
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We can prove that again.
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Let's go to decimal 240 is that in hexadecimal 2 to 4 in decimal is that in hexadecimal and 255 in decimal.
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Is that in hexadecimal.
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There are the hexadecimal equivalents for these decimal values.
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Make sure that you know how to convert numbers from decimal to hexadecimal.
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Why does this become important because as an example this is a broadcast address in IP version 4.
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So in IP version 4 that means all devices on the network 255.
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Looks like that in binary it's eight binary ones 128 plus 64 plus 32 plus sixteen plus eight plus four
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plus two plus one so 255 looks like that four times if you take each of these four binary bits each
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of those equals F so we've got f f so in hexadecimal a broadcast looks like this that is a broadcast
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address.
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So on this P.C. I'm gonna ping 255 255 255 255.
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What I'll do is put this into simulation mode so we can see what's actually going on and I'll press
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enter.
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It doesn't like that in packet tracer.
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So let's ping 10 1 1 1 255.
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It's okay with us sending that traffic into the network.
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So I'll send the packet into the network and if we have a look at that packet notice the source mac
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address is the P.C. but the destination MAC address is a bunch of F's.
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Now that isn't actually a proper conversion of this IP address to broadcast but because it's what's
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called a link local broadcast we've broadcast to all the devices in the local segment Packet Tracer
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showing it like that.
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So the inbound PDA or protocol data unit shows us.
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Source MAC addresses this destination MAC addresses a bunch of FS source IP address and it's actually
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done a conversion of setting the destination IP address to 255 255 255 255.
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So even though it didn't accept that command pinging that address it actually converted that IP address
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to all hosts all networks broadcast and hence we have that at layer too.
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So once again there's the Layer 3 IP address destination is 255 255 255 255.
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And at least two it's all F's.
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Now that you understand hexadecimal conversions you understand why it did that.
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This add layer 3 looks like this at least two but a MAC address is actually 48 bits in size so it's
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folded in and it looks like this.
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We have twelve FS not eight FS like in this conversion here Mac addresses once again 12 but not simply
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8 bits.
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That's not an exact conversion like I've shown you but that's the hexadecimal equivalent of this IP
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address this IP address looks like this in binary that is binary 10 1 1 1.
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Again that's 8 that's two equals 10.
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So I'll clear that up if we split that in half.
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Notice here's a mistake.
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This is not hexadecimal.
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This is actually zero in hex and that being 10 1 0 1 0 is a.
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So it should be 0 a going back 10 in decimal is a in hexadecimal or this in binary.
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So take the decimal number convert it to binary.
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This is an IP address so it's a two bits.
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So not text zero a which in hexadecimal looks like that one in decimal looks like that in binary which
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looks like that in hexadecimal.
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Why.
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Because if we split this down the middle.
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That is a zero in hex.
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That is a 1 in hex.
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Looks like that for those three numbers.
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And if we look at two to four one two three that's two to four in binary one two three split it down
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the middle.
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That would have been a one.
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This is 2 4 8 8 plus four plus two equals fourteen which equals E in hexadecimal.
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This is zero.
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So we get easier the next one is 0 1 that's 0 that's 1 0 2 0 3.
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I've gone through a few examples hopefully that makes sense.
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Let me know if you still struggling with the theory of this but to help you.
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I've created a whole bunch of converters that can help you study.
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So as an example if I click on the first link and by the way I've given you this PowerPoint presentation
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so look at the attachments and you can download keep it for reference but you also have access to this
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converter.
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If I put a number in here like 128 another 1 2 2 4 255 255 and click convert you'll see the decimal
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binary and hex numbers and then it's done an inverse.
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So that's one followed by seven zeros.
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The inverse of that would be zero followed by seven ones which looks like that as an inverse hex number.
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So again there's the decimal number.
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There's the binary number and here's the hex number.
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And then we've got inverse of that.
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There's also a binary two decimal visual calculator.
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So if I put in a number here like 240 you'll notice that the binary string looks like that.
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This can help you work out binary numbers if you're not sure.
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240 minus 128 gives us 112 because that boat is set on we subtract 128 from 240.
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Reset that bit on we subtract 64 from 112.
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Gives us 48 and then that but on means 32 subtract from 48 gives us sixteen that bet on means sixteen
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subtracted from sixteen gives us zero.
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So the remaining bits are sector zero.
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So we've got four binary ones followed by four binary zeros for a number of 240.
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But this is probably what you're gonna be more interested in.
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I've got an unlimited hexadecimal to decimal quiz here.
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So if you've been given this hex value what is the equivalent decimal value.
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You can put in the value that you think it is.
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Let's say 1 2 3.
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Click check on it and it tells you that you've got a wrong.
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You can try that as many times as you like.
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And if you're not sure click give up and then it gives you the decimal equivalent number so you can
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use this to test your knowledge of in conversions from hex to decimal.
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You can also go through a quiz question asking you what this is in hexadecimal.
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Hopefully you'll remember that from what we studied.
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Click Submit it tells us that we've got the answer correct.
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So you can go through a whole bunch of course questions if you'd like.
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On David bubble dot com.
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OK so it's important that you know how to work with hexadecimal because you'll find it in many places
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and networking make sure that you understand the theory that you can do the conversions in the real
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world we'd use calculators but you need to know the theory first to understand how things work so that
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you can troubleshoot networks work with IP version 6 addresses and mac addresses and so forth.
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Again let me know if you need more examples but hopefully that makes sense and you can use the quiz
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questions and online calculators to help you practice.
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