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                                     5




                                 Disk Drive 























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Chapter 5 - Disk Drive


     Every computer must have some way of adding new software to the
computer, saving something you've worked on, (like a word processing document)
and in general storing the software the computer needs to operate.  This is 
where "computer disk drives" come in.  Disk drives are used to store data about 
anything you want and this data can be changed at anytime.  Therefore, when the 
computer is turned off, whatever you wanted to save isn't lost, and is still 
there the next time you turn the computer on.  There are several different types 
of disk drives such as Floppy Disk Drives, Hard Disk Drives, and CD-ROM drives 
(CD-ROM drives are discussed in Chapter 10 - Multi-Media).

     A Floppy Disk is a thin piece of magnetic plastic surrounded by another 
piece of non-magnetic plastic.  The floppy disk was invented some twenty years 
ago as a way of reliably storing computer data and information.  Floppy disks 
require a "Floppy Disk Drive" to be written to, read from, or erased, but the 
actual floppy disk can be removed from the floppy disk drive at anytime.  Since 
the floppy disk can be removed from the floppy disk drive, it can easily be used 
on multiple computers to share information between computers.  Since the first 
floppy disks were so large (over a foot in diameter) and were so thin, they 
tended to sag or "flop" over when being handled.  Therefore, as you may have 
guessed, they were named "floppy diskettes". Originally "diskette" was the 
correct name, but over the years people shorted the name to "disk" so now both 
"disk" and "diskette" are considered correct. 

     Through the years, because of their ease of use, floppy disks have been 
used on virtually every computer made, and are still widely used today.  Due to 
this popularity, manufacturers have continued to improve the floppy disk (and 
their drives) so today, floppy disks are far superior to floppy disks of the 
earlier days.  For example: Floppy disks are now considerably smaller than older 
style disks (down to 3  inches wide).  Modern floppy disks can now hold 
thousands of pages of typed information (like in a word processing document) 
while floppy disks from those early years could only hold a few typed pages.  
Newer floppy disk drives can also read, write, erase considerably faster than 
those early disk drives.  

     When IBM developed floppy disks (and their disk drives) for use in their 
first Personal Computers (PC) they used a floppy disk that was 5  inches wide.  
This 













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size has been popular ever since, but in recent years has lost popularity 
and is not even included on most new computers.  Sony was the company that 
caused the lost popularity in 5  floppy disks because they developed a smaller 
disk that can also hold more information.  It is called a 3  inch disk and is 
unlike other floppy disks because instead of a soft, flexible outer cover (like 
used on 5  disks) they use a hard plastic cover.  The 3  disk is still 
considered a floppy disk, but it is literally no longer "floppy".  As a result 
of this, people sometimes confuse the 3  floppy disk with a "hard disk drive".  
See Figure 5a below.  We'll cover hard disk drives later.


                             ---------------------
                             |-----------------  |
                             ||               | _|
        -------------        ||               | | 
        |O|       |O|        |-----------------  |
        | |       | |        |        ___        |
        | |       | |        |       /   \       |
        | |       | |        |      /     \      |
        | --------- |        |      |     |      |
        |           |        |      \     /      |
        |  ------   |        |       \___/       |
        |  | |  |   |        |                   |
        |  | |  |   |        |        ---        |
        -------------        |        | |        |
                             |        | |        |
                             |        | |        |
                             |        ---        |
                             ---------------------


           3 1/2                     5 1/4


        Figure 5a - Examples of 3 1/2 and 5 1/4 inch disks.


     New computers will likely come with one 3  floppy disk drive.  As I said
before, since the 5  floppy disks have lost popularity, most manufacturers won't
include a 5  floppy disk drive unless you request it and pay extra for it.  Some
software manufacturers have even stopped selling their software on 5  floppy
disks.  








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     Currently floppy disk manufacturers still sell four different types of 
floppy disks.  Of these four types there are two sizes (5  and 3 ) and four 
different amounts of information the floppy disks can hold.  This sounds harder 
than it really is so let me explain.  Every floppy disk has a certain "density", 
and that means how much data that floppy disk will hold.  Just like a 5 gallon 
bucket will hold more water than a 1 gallon bucket; a "high density" (also known 
as HD) floppy disk will hold more information than a "low density" floppy disk.  
All new floppy disk drives are considered "high density", which means they can 
use a floppy disk that is considered "high density".   In addition, high density 
floppy disk drives can use low density floppy disks.  The low density floppy 
disk will still hold less than a high density floppy disk, but you can use them 
with your floppy disk drive.  You cannot, however use a high density floppy disk 
in a low density floppy disk drive.  To make matters a little more confusing 
sometimes floppy disks are referred to by their storage capacity rather than by 
their size.  Consider the following chart:

Disk Size     Disk Density     Disk Capacity     Number of full, typed pages
---------     ------------     -------------     ---------------------------
  5          Low density      360 kilobytes              68 pages       
  5          High density     1.2 megabytes              229 pages
  3          Low density      720 kilobytes              138 pages
  3          High density     1.44 megabytes             276 pages

* Note:   Currently, there are 3  disks that have a capacity of 2.88 megabytes,
          but these disks (and the floppy disk drives that use them) are more
          expensive, and not commonly seen in new computers.


     There is really no reason to buy anything less than high density floppy 
disks unless you intend to use those diskettes on a computer that can't use high 
density disks.  There is only a small difference in price between high density 
and low density floppy disks.

     There is another type of disk drive called a "Hard Disk Drive" (also called 
a "fixed disk drive").  It is similar to floppy disk drives in several ways such 
as it can read, write, erase your data.  However, that's generally where the 
similarities end.  The hard disk drive is usually hidden inside the computer.  
The reason it is called a hard disk drive is because the internal disk is made 
of metal.  A hard disk drive does 











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not have removable disks (a few, very select hard drives have removable disks, 
but these are not common). 

     Virtually every computer sold today comes with some type of hard disk 
drive.  You may be asking yourself "If I have a floppy disk drive then why do I 
need a hard disk drive?"  Here's your answer.  The average hard disk drive to 
come with a computer today holds 740 megabytes to 1 gigabyte (1024 megabytes).  
Compare that to the 1.44 megabytes one floppy disk will hold.  The average 
program today will require at least six megabytes.  Are you starting to see the 
problem here.  WordPerfect 6.1 for Windows comes on eleven 1.44 megabyte 
floppies and will not work until it is installed on a hard disk drive.  Hard 
disk drives have been able to keep up with the current program sizes, but floppy 
disk have not.  Therefore, virtually all of the software you can buy today must 
be installed on your hard disk drive.

     Besides the obvious advantage in the amount of information a hard drive can
hold compared to a floppy disk, there is another important advantage.  The 
average hard drive can read, save, and erase your information up to 100 times 
faster than a floppy disk drive so you're spending less time waiting on the 
computer.

     Hard disk drives have a variety of capacities (just like floppy disks) and 
the average hard drive sold today is 740 megabytes 1 gigabyte.  In the last few 
years, the prices of hard disk drives has fallen dramatically while their 
capacities have gone through the roof.  Having a 1 gigabyte hard drive on a 
personal computer even 5 years ago would of been totally unheard of.  This trend 
of lower prices and higher capacities is continuing so in the next few months 
the average capacity of a hard drive sold with new computers will be either 1.2 
or 1.6 gigabytes.  If you feel you need even more capacity than that, larger 
drives are available and have over 2.0 gigabytes.

     There has always been competition in the market place for companies to
make faster, higher capacity, physically smaller hard disk drives.  Therefore, a
number of different types of hard disk are available such as Enhanced IDE 
(EIDE), IDE and SCSI (pronounced Enhanced I-D-E,  I-D-E and scuzzy).  There are
actually several types of SCSI hard drives, but since most people aren't likely 
to













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ever use SCSI, I'm not going to discuss them.  Now I know what you're thinking 
"What in the world do these letters mean?"  That's not important, but what's 
important is virtually every new computer being sold now uses either an EIDE or 
an IDE type of hard disk drive.  When you're out looking at computers, ask if 
the computer has an IDE or EIDE hard drive, because that will give you a clue 
to how "up-to-date" the computer and the manufacturer are.  EIDE is a newer and 
faster version of IDE, and has been available for the past several years.  There
is no cost difference between an EIDE and IDE hard drive made by the same 
manufacturer for the same capacity drive.  There is, however, a 10-40 percent 
difference in how much or how fast the drive can do something.  Therefore, you 
definitely want an EIDE hard drive, and not an IDE hard drive. 







































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