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FAT System Guide


FAT System Guide

The DOS Zone

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Introduction To Disks.

Use this information only if you agree to the terms in my Disclaimer

    As you hopefully know, a disk is something that you use to store all your files on, but have you ever considered how it actually stores this data? In this section you will hopefully learn about the operation of disks below the file and directory level.

If you buy yourself a bucket then you'll have one big container which can store whatever you want it to, a disk is a little different it's not organised as one big storage area but split into many smaller areas, these are called sectors. I think that a notepad is a good analogy for a disk, each piece of paper can be compared to a sector. When you write a letter you keep writing until there's no more room on the piece of paper at which point you continue on a second, the point I'm trying to make here is that you are splitting one large amount into smaller amounts rather than use one big bit of paper. This is very basically how a disk functions.

Imagine that you have a notepad, in this notepad you begin to write your shopping list when you get a phone call which requires you to take down an address, you write this down on the next available page then flip back to the shopping list and carry on until you run in to the address you have just written. You now have two options, one rip out the page with the address or two carry on on the next available page, you cannot remove the page (because my analogy would fall to pieces) so you use option two and continue on the next available page. Your notepad now looks like this:

Page 1Page 2Page 3
Shopping List part 1AddressShopping List part 2

In the above example you would be able to work out what was what just by reading what you'd written, a computer on the other hand would have no idea which bit belonged where so obviously some form of organisation is called for. This is where the file system comes in, it provides a method of keeping track of the data. If you're going to do that then obviously you'll need to dedicate some sectors to this task, think about a book, it uses some pages as an index has a contents page etc.

In the following sections you will discover how the FAT (file allocation table) system goes about organising files.

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