WEBVTT

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 Okay, so let's talk a little about file
 identifications and their structures.

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 So usually the simplest way to determine
 a file's type is by just looking

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 at its extension, right?

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 That's where you see if it's a word
 file, it's a DOCX, if it's an Adobe

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 document, it's a PDF, if it's even a
 word file, if it's even an Outlook

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 mailbox file, right?

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 It's usually going to
 be a PST file, right?

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 So a lot of times that extension is
 going to associate the file type to

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 the program that uses it,
 especially in Windows.

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 But what if there's an
 extension mismatch?

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 What happens to a file when the file
 extension is changed to something

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 incompatible? The default application
 will try to open it, but it will

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 fail to be able to open it and it
 will give you some type of error.

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 You can give this a try, right?

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 You can change a PDF file to a DOCX
 file that's word to Adobe, and what

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 you will give is an error
 when you try to open it.

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 If you change it back,
 you can open it again.

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 The Windows operating system
 doesn't check this for you.

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 So it isn't until the application tries
 to read the unsupported file,

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 but there's going to be a problem.


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 And that's because with Windows, the
 extensions are used to determine

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 what applications should be used to open
 a file, but changing the extension

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 doesn't change the file extension.


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 On the flip side of that, though, Linux
 will use a file signature to determine

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 what type of program
 should be used.

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 So just think that what we're talking
 about in this specifically points

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 to Windows. So let's talk about file
 signature because we've mentioned

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 that a few times, right?

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 Files have headers.

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 Headers exist at the beginning of the
 file, and then they also have footers,

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 and footers will exist
 at the end of the file.

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 The header could contain something like
 the name of the author, the data

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 creation, size, or other data that helps
 performing error detection and

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 correction before
 opening the file.

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 Not all file types have the same signatures,
 but the signature verification

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 is a good way to identify when
 an extension is correct.

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 And what this provides
 us is some consistency.

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 It's worth noting that file structures
 remain the same across operating

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 systems. A PDF created on a Windows
 computer will look the same as a PDF

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 created on a Mac, and this allows our
 files to be shared across operating