Hard disks store digital information in a relatively permanent form. See more hard disk pictures.

Nearly every desktop computer and server in use today contains one or more hard-disk drives. Every mainframe and supercomputer is normally connected to hundreds of them. You can even find VCR-type devices and camcorders that use hard disks instead of tape. These billions of hard disks do one thing well -- they store changing digital information in a relatively permanent form. They give computers the ability to remember things when the power goes out.
In this article, we'll take apart a hard disk so that you can see what's inside, and also discuss how they organize the gigabytes of information they hold in files!








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Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes. They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disks." Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.
At the simplest level, a hard disk is not that different from a cassette tape. Both hard disks and cassette tapes use the same magnetic recording techniques described in How Tape Recorders Work. Hard disks and cassette tapes also share the major benefits of magnetic storage -- the magnetic medium can be easily erased and rewritten, and it will "remember" the magnetic flux patterns stored onto the medium for many years.
In the next section, we'll talk about the main differences between casette tapes and hard disks.


Let's look at the big differences between cassette tapes and hard disks:

• The magnetic recording material on a cassette tape is coated onto a thin plastic strip. In a hard disk, the magnetic recording material is layered onto a high-precision aluminum or glass disk. The hard-disk platter is then polished to mirror-type smoothness.
• With a tape, you have to fast-forward or reverse to get to any particular point on the tape. This can take several minutes with a long tape. On a hard disk, you can move to any point on the surface of the disk almost instantly.
• In a cassette-tape deck, the read/write head touches the tape directly. In a hard disk, the read/write head "flies" over the disk, never actually touching it.
• The tape in a cassette-tape deck moves over the head at about 2 inches (about 5.08 cm) per second. A hard-disk platter can spin underneath its head at speeds up to 3,000 inches per second (about 170 mph or 272 kph)!
• The information on a hard disk is stored in extremely small magnetic domains compared to a cassette tape's. The size of these domains is made possible by the precision of the platter and the speed of the medium.

­ Because of these differences, a modern hard disk is able to store an amazing amount of information in a small space. A hard disk can also access any of its information in a fraction of a second.


A typical desktop machine will have a hard disk with a capacity of between 10 and 40 gigabytes. Data is stored onto the disk in the form of files. A file is simply a named collection of bytes. The bytes might be the ASCII codes for the characters of a text file, or they could be the instructions of a software application for the computer to execute, or they could be the records of a data base, or they could be the pixel colors for a GIF image. No matter what it contains, however, a file is simply a string of bytes. When a program running on the computer requests a file, the hard disk retrieves its bytes and sends them to the CPU one at a time.
There are two ways to measure the performance of a hard disk:

• Data rate - The data rate is the number of bytes per second that the drive can deliver to the CPU. Rates between 5 and 40 megabytes per second are common.
• Seek time - The seek time is the amount of time between when the CPU requests a file and when the first byte of the file is sent to the CPU. Times between 10 and 20 milliseconds are common.

The other important parameter is the capacity of the drive, which is the number of bytes it can hold.

The best way to understand how a hard disk works is to take a look inside. (Note that OPENING A HARD DISK RUINS IT, so this is not something to try at home unless you have a defunct drive.)
Here is a typical hard-disk drive:


­It is a sealed aluminum box with controller electronics attached to one side. The electronics control the read/write mechanism and the motor that spins the platters. The electronics also assemble the magnetic domains on the drive into bytes (reading) and turn bytes into magnetic domains (writing). The electronics are all contained on a small board that detaches from the rest of the drive:



Underneath the board are the connections for the motor that spins the platters, as well as a highly-filtered vent hole that lets internal and external air pressures equalize:


Removing the cover from the drive reveals an extremely simple but very precise interior:


In this picture you can see:

• The platters - These typically spin at 3,600 or 7,200 rpm when the drive is operating. These platters are manufactured to amazing tolerances and are mirror-smooth (as you can see in this interesting self-portrait of the author... no easy way to avoid that!).
• The arm - This holds the read/write heads and is controlled by the mechanism in the upper-left corner. The arm is able to move the heads from the hub to the edge of the drive. The arm and its movement mechanism are extremely light and fast. The arm on a typical hard-disk drive can move from hub to edge and back up to 50 times per second -- it is an amazing thing to watch!

In order to increase the amount of information the drive can store, most hard disks have multiple platters. This drive has three platters and six read/write heads:



The mechanism that moves the arms on a hard disk has to be incredibly fast and precise. It can be constructed using a high-speed linear motor.




Many drives use a "voice coil" approach -- the same technique used to move the cone of a speaker on your stereo is used to move the arm.


Data is stored on the surface of a platter in sectors and tracks. Tracks are concentric circles, and sectors are pie-shaped wedges on a track, like this:


A typical track is shown in yellow; a typical sector is shown in blue. A sector contains a fixed number of bytes -- for example, 256 or 512. Either at the drive or the operating system level, sectors are often grouped together into clusters.
The process of low-level formatting a drive establishes the tracks and sectors on the platter. The starting and ending points of each sector are written onto the platter. This process prepares the drive to hold blocks of bytes. High-level formatting then writes the file-storage structures, like the file-allocation table, into the sectors. This process prepares the drive to hold files.

Floppy disk drives were a key computer component for 20 years.  See more pictures of floppy disk drives.

If you have spent any time at all working with a computer, then chances are good that you have used a floppy disk at some point. The floppy disk drive (FDD) was the primary means of adding data to a computer until the CD-ROM drive became popular. In fact, FDDs have been a key component of most personal computers for more than 20 years. Basically, a floppy disk drive reads and writes data to a small, circular piece of metal-coated plastic similar to audio cassette tape. In this article, you will learn more about what is inside a floppy disk drive and how it works. You will also find out some cool facts about FDDs.

The floppy disk drive (FDD) was invented at IBM by Alan Shugart in 1967. The first floppy drives used an 8-inch disk (later called a "diskette" as it got smaller), which evolved into the 5.25-inch disk that was used on the first IBM Personal Computer in August 1981. The 5.25-inch disk held 360 kilobytes compared to the 1.44 megabyte capacity of today's 3.5-inch diskette. The 5.25-inch disks were dubbed "floppy" because the diskette packaging was a very flexible plastic envelope, unlike the rigid case used to hold today's 3.5-inch diskettes.
By the mid-1980s, the improved designs of the read/write heads, along with improvements in the magnetic recording media, led to the less-flexible, 3.5-inch, 1.44-megabyte (MB) capacity FDD in use today. For a few years, computers had both FDD sizes (3.5-inch and 5.25-inch). But by the mid-1990s, the 5.25-inch version had fallen out of popularity, partly because the diskette's recording surface could easily become contaminated by fingerprints through the open access area.

Floppy Disk Drive Terminology Floppy disk - Also called diskette. The common size is 3.5 inches. Floppy disk drive - The electromechanical device that reads and writes floppy disks. Track - Concentric ring of data on a side of a disk. Sector - A subset of a track, similar to wedge or a slice of pie.

The Disk
A floppy disk is a lot like a cassette tape:

• Both use a thin plastic base material coated with iron oxide. This oxide is a ferromagnetic material, meaning that if you expose it to a magnetic field it is permanently magnetized by the field.
• Both can record information instantly.
• Both can be erased and reused many times.
• Both are very inexpensive and easy to use.

If you have ever used an audio cassette, you know that it has one big disadvantage -- it is a sequential device. The tape has a beginning and an end, and to move the tape to another song later in the sequence of songs on the tape you have to use the fast forward and rewind buttons to find the start of the song, since the tape heads are stationary. For a long audio cassette tape it can take a minute or two to rewind the whole tape, making it hard to find a song in the middle of the tape. A floppy disk, like a cassette tape, is made from a thin piece of plastic coated with a magnetic material on both sides. However, it is shaped like a disk rather than a long thin ribbon. The tracks are arranged in concentric rings so that the software can jump from "file 1" to "file 19" without having to fast forward through files 2-18. The diskette spins like a record and the heads move to the correct track, providing what is known as direct access storage.

In the illustration above, you can see how the disk is divided into tracks (brown) and sectors (yellow).

The Drive
The major parts of a FDD include:

• Read/Write Heads: Located on both sides of a diskette, they move together on the same assembly. The heads are not directly opposite each other in an effort to prevent interaction between write operations on each of the two media surfaces. The same head is used for reading and writing, while a second, wider head is used for erasing a track just prior to it being written. This allows the data to be written on a wider "clean slate," without interfering with the analog data on an adjacent track.
• Drive Motor: A very small spindle motor engages the metal hub at the center of the diskette, spinning it at either 300 or 360 rotations per minute (RPM).
• Stepper Motor: This motor makes a precise number of stepped revolutions to move the read/write head assembly to the proper track position. The read/write head assembly is fastened to the stepper motor shaft.
• Mechanical Frame: A system of levers that opens the little protective window on the diskette to allow the read/write heads to touch the dual-sided diskette media. An external button allows the diskette to be ejected, at which point the spring-loaded protective window on the diskette closes.
• Circuit Board: Contains all of the electronics to handle the data read from or written to the diskette. It also controls the stepper-motor control circuits used to move the read/write heads to each track, as well as the movement of the read/write heads toward the diskette surface.

The read/write heads do not touch the diskette media when the heads are traveling between tracks. Electronic optics check for the presence of an opening in the lower corner of a 3.5-inch diskette (or a notch in the side of a 5.25-inch diskette) to see if the user wants to prevent data from being written on it.

Click on the picture to see a brief video of a diskette being inserted. Look for the silver, sliding door opening up and the read/write heads being lowered to the diskette surface.

Read/write heads for each side of the diskette

The following is an overview of how a floppy disk drive writes data to a floppy disk. Reading data is very similar. Here's what happens:

1. The computer program passes an instruction to the computer hardware to write a data file on a floppy disk, which is very similar to a single platter in a hard disk drive except that it is spinning much slower, with far less capacity and slower access time.
2. The computer hardware and the floppy-disk-drive controller start the motor in the diskette drive to spin the floppy disk. The disk has many concentric tracks on each side. Each track is divided into smaller segments called sectors, like slices of a pie.
   
3. A second motor, called a stepper motor, rotates a worm-gear shaft (a miniature version of the worm gear in a bench-top vise) in minute increments that match the spacing between tracks. The time it takes to get to the correct track is called "access time." This stepping action (partial revolutions) of the stepper motor moves the read/write heads like the jaws of a bench-top vise. The floppy-disk-drive electronics know how many steps the motor has to turn to move the read/write heads to the correct track.
   
4. The read/write heads stop at the track. The read head checks the prewritten address on the formatted diskette to be sure it is using the correct side of the diskette and is at the proper track. This operation is very similar to the way a record player automatically goes to a certain groove on a vinyl record.
5. Before the data from the program is written to the diskette, an erase coil (on the same read/write head assembly) is energized to "clear" a wide, "clean slate" sector prior to writing the sector data with the write head. The erased sector is wider than the written sector -- this way, no signals from sectors in adjacent tracks will interfere with the sector in the track being written.
6. The energized write head puts data on the diskette by magnetizing minute, iron, bar-magnet particles embedded in the diskette surface, very similar to the technology used in the mag stripe on the back of a credit card. The magnetized particles have their north and south poles oriented in such a way that their pattern may be detected and read on a subsequent read operation.
7. The diskette stops spinning. The floppy disk drive waits for the next command.

On a typical floppy disk drive, the small indicator light stays on during all of the above operations.
Here are some interesting things to note about FDDs:

• Two floppy disks do not get corrupted if they are stored together, due to the low level of magnetism in each one.
• In your PC, there is a twist in the FDD data-ribbon cable -- this twist tells the computer whether the drive is an A-drive or a B-drive.
• Like many household appliances, there are really no serviceable parts in today's FDDs. This is because the cost of a new drive is considerably less than the hourly rate typically charged to disassemble and repair a drive.
• If you wish to redisplay the data on a diskette drive after changing a diskette, you can simply tap the F5 key (in most Windows applications).
• In the corner of every 3.5-inch diskette, there is a small slider. If you uncover the hole by moving the slider, you have protected the data on the diskette from being written over or erased.
• Floppy disks, while rarely used to distribute software (as in the past), are still used in these applications:
  • in some Sony digital cameras
  • for software recovery after a system crash or a virus attack
  • when data from one computer is needed on a second computer and the two computers are not networked
  • in bootable diskettes used for updating the BIOS on a personal computer
  • in high-density form, used in the popular Zip drive

The word "disk defrag" is typically used to refer to the Microsoft Windows utility called Disk Defragmenter. It is designed to solve a problem that occurs because of the way hard disks store data.
If you have read the article How Hard Disks Work, then you know three key facts about hard disks:

1. Hard disks store data in chunks called sectors. If you imagine the surface of the disk divided into rings (like the rings of a tree), and then imagine dividing each ring into pie-slices, a sector is one pie-slice on one ring. Each sector holds a fixed amount of data, like 512 bytes.
2. The hard disk has a small arm that can move from ring to ring on the surface of the disk. To reach a particular sector, the hard disk moves the arm to the right ring and waits for the sector to spin into position.
3. Hard disks are slow in computer terms. Compared to the speed of the processor and its memory, the time it takes for the arm to move and for a sector to spin into place is an eon.
   
   

Because of fact #3, you want to minimize arm movement as much as possible, and you want data stored in sequential segments on the disk.
So let's imagine that you install a new application onto an empty hard disk. Because the disk is empty, the computer can store the files of the application into sequential sectors on sequential rings. This is an efficient way to place data on a hard disk.
As you use a disk, however, this efficient technique becomes harder for a disk. What happens is that the disk fills up. Then you erase files to reclaim space. These files that you delete are scattered all over the surface of the disk. When you load a new application or a large file onto the disk, it ends up being stored in hundreds or thousands of these scattered pockets of space. Now when the computer tries to load the scattered pieces, the disk's arm has to move all over the surface and it takes forever.
The idea behind the disk defragmenter is to move all the files around so that every file is stored on sequential sectors on sequential rings of the disk. In addition, a good defragmenter may also try to optimize things even more, for example by placing all applications "close" to the operating system on the disk to minimize movement when an application loads. When done well on older disks, defragmenting can significantly increase the speed of file loading. On a new disk that has never filled up or had any significant number of file deletions, it will have almost no effect because everything is stored sequentially already.
As you might imagine, the process of indivdually picking up and moving thousands of files on a relatively slow hard disk is not a quick process -- it normally takes hours.


Starting with Windows 98, the defragmenter places the data on the hard drive in the same sequence Windows uses it. The Windows 98 defragmenter also knows what programs you run the the most often, and places those on the disk so the computer can access it the fastest possible time.
For the defragmenter to properly run, ensure you have no applications running. Typically, SYSTRAY and EXPLORER are all you need to have running to run this application. You can see the active tasks you have running by doing a "three-finger-salute" (Ctrl+Alt+Del). Disable any screen saver in use, too. The defragmenter will fail to stay running if your system is constantly accessing some other application like Findfast.exe, a resource user that automatically gets installed with Microsoft office. To prevent Findfast.exe from running at every system boot, simply delete it from your Windows STARTUP folder, or look for the Findfast icon in control panel and change its setting.
The defragmenter can take a considerable time to run, so start the Defragmenter before going out for the evening or at the end of the day, before going to sleep.

Do you own a computer that is more than a year old? If so, then you may be running out of disk space. In the same way that closets and attics have a way of filling up and overflowing, so do hard drives. Maybe your 8-megapixel camera needs a gigabyte of disk space every time you unload the camera's memory card. Or your MP3 collection grows by 10 songs every day. Perhaps you are trying to edit videos of the kids, and every 5 minutes of tape consumes a gigabyte of disk space. Or maybe you would like to add a TV tuner card to your machine and turn your computer into a DVR. Digital cameras, video cameras, MP3 players and TV tuner cards all consume lots of disk space. If you use any of these gadgets, chances are that you need more space. In this article, we will show you how easy it is to add a new hard drive to your existing machine.

Photo courtesy Amazon An additional hard drive provides more disk space on your computer.

Before we start the process of adding a drive, we need to do a small amount of research inside your machine. The goal of the research is to find out if it will be easy or not so easy to add the new hard drive. We also need to find out what kind of drive you need to buy. You may be able to do this research by reading through your computer's manuals, but it is far easier to simply open the case and look inside.
The first question to answer is: How many hard disk drives have already been installed inside the case? In the majority of machines, the answer to this question is "one." Having only one hard disk drive installed makes it easy to install another one. After you open up your computer's case and look inside, you will probably find one optical drive (a CD or DVD drive), a single hard disk drive and perhaps a floppy disk drive. The optical and floppy drives will be easy to find because you can see them on the outside of the case. The hard drive may take a little searching. If you have no idea what a hard drive looks like, look at the photo above.
If there are already two drives installed inside your case, then adding a new one is more difficult. Check out the section on adding an external drive later in this article.

This cage contains two hard drives. If the computer's user wanted an additional hard drive, he would have to add an external one.

Is there space available to add another hard-disk drive? Your current hard disk is probably mounted in a small metal cage or rack inside the machine. Make sure there is space available in the cage for another drive. If not, look at the section on adding an external drive.
Find out what type of cable system is used to connect drives to the motherboard. There are two systems in common use: IDE drives (also known as PATA, or Parallel ATA), and SATA (Serial ATA) drives. PATA drives have wide, flat cables or thick cables as wide as your finger, while SATA drives have thin cables about the diameter of a pencil. You will need to know whether to buy an IDE or SATA drive, and you should be able to tell by looking at the cables.

An IDE, or PATA hard drive, uses a wide, flat or thick cable to connect to the computer's motherboard.

A SATA hard drive uses thin cables about the diameter of a pencil to connect to the computer's motherboard.

Now that you have confirmed that there is space to install a new drive in your machine and you know what type of drive you need (PATA or SATA), you can buy a new drive.

SCSI Hard Drives? There is a chance that your computer contains SCSI (pronounced "scuzzy") hard drives. If we are talking about a normal, mass-market PC, however, the chance is pretty slim. If in doubt, see the photos of SCSI cables and learn more about SCSI in How SCSI Works.

You can buy a new hard drive from many different places: a retail store, a large computer store, a local computer parts store or by mail order. Wherever you go to buy it buy it, keep three things in mind:

• Buy a "normal" 3.5-inch wide hard drive. They're sold everywhere, but you want to avoid the smaller hard disk drives made for laptops.
• Make sure the new drive has the correct cable system (SATA or PATA) to match your machine.
• Make sure the drive is big.Buy the biggest drive you can afford, because it will probably fill up before you know it.

Now that you have your new drive, you are ready to install it. Before we start working with the drive, we need to talk about static electricity. Your computer is highly sensitive to static shocks. This means that if you build up static electricity on your body and a shock passes from your body to something like a hard drive, that hard drive is dead and you will have to buy another one.

To avoid passing static electricity to your new hard drive, you can wear an inexpensive grounding bracelet.

The way to eliminate static electricity is by grounding yourself. There are lots of ways to do this, but probably the easiest way is to wear a grounding bracelet on your wrist. Then you connect the bracelet to something grounded (like a copper pipe or the center screw on a wall outlet's face plate). By connecting yourself to ground, you eliminate the possibility of static shock. You can get a bracelet for a few dollars.
Installing a new disk drive is easy. You have five basic steps: setting the jumpers, mounting the drive, plugging in the power connector, connecting the cable and configuring the drive.
First, set the jumpers (if it is an IDE drive). Let's talk about this in more detail, because most people have IDE drives.


In the IDE system, most motherboards allow you to have two IDE cables. Each cable can connect to two drives. Usually you use one cable to connect one or two optical drives to your machine. The other cable is used to connect one or two hard drives to your machine.
You want both hard drives to be on the same cable. The two drives on the cable are called "master" and "slave." You want your existing hard drive (which contains the operating system and all of your current data) to be the "master" and the new hard drive to be the "slave." The drive should have instructions on them that tell you how to set the jumpers for master and slave. So read the instructions and set the jumpers. If you are using SATA drives, you do not need to set jumpers for master and slave because each drive gets its own cable. Check out How IDEs Work to learn more about the master and slave configuration.
Now that the jumpers are set correctly, mount the new drive in your drive cage and screw it into place.
Next, plug in the drive's power connector to the power supply. If it fits, then it's a match.
Connect the IDE or SATA cable to the drive.
Close the machine, power it up and configure your new drive using the Windows XP drive administration tool. To do this, click the Start button, open the Control Panel, Switch to Classic View, click on Administrative Tools, click on Computer Management, click on Disk Management. You will see something that looks like this:

The last step in the process of adding a new hard drive is formatting that hard drive using the Windows XP drive adminstration tool.

Look at the graphical area in the bottom right of this display. Disk 0 is your original hard drive. Disk 1 is the new hard drive. Chances are that the new drive will not be initialized , or formatted. Click the small button to initialize the drive, and then format it as an NTFS volume (right click on the new drive, then click “Format...”). Formatting may take an hour or more, so be patient.
When the formatting is done, you are ready to use your new drive.

For lots more information on hard drives, computers and more, check out the links on the next page.

External Hard Drives Suppose you want to add another hard drive, but there's no more space in your case to add another drive. In that case, consider adding an external drive. They connect to your computer through either a USB 2.0 connection or a FireWire connection, so your computer needs to have USB 2.0 or FireWire connectors. Once you buy the drive, all you have to do is connect it and fire up your computer. The drive will come with configuration instructions, but on Windows XP it will likely be plug-and-play. You can start saving files on your new drive immediately. There is one big advantage to an external drive: you can plug it into multiple machines and move files around. You can take it with you anywhere you go. The only real disadvantage is that it will be slower than an internal drive. If it takes a minute to copy a gigabyte of data on an internal drive, it might take two minutes on an external drive. That may or may not be important depending on what you want to do. For most applications, the slower speed is irrelevant.

In the article How Hard Disks Work, you can see that the read/write heads do not touch the platters in the drive. When the platters spin up, they rotate at anywhere between 3,600 rpm and 7,200 rpm. To the head, the platter seems to be moving at about 150 mph, and a very thin cushion of air forms between the head and the platter so that the head "flies" over the platter. If even the smallest bit of dust makes its way onto the platter, the flight is disrupted and the head "crashes" into the platter, scratching it. The crash, of course, sprays a lot more dust and debris onto the platter and then it's all over.
The other thing that can cause a squealing sound is the bearings in the drive motor. That is another common way for a drive to fail.
Hard disks are amazingly reliable these days, with "Mean Time Between Failures" (MTBF) of 500,000 to 1,000,000 hours. That means that, on average, a drive fails after the specified number of hours, with half of the drives lasting more than that and half lasting less. 500,000 hours is about 57 years. Clearly, not all drives last 57 years, so frequent backups are important.

Let's say you do something simple like double-click on the icon for a spreadsheet file. This simple act, on many computers, can take 20 or 30 seconds to complete, and all during that time the hard disk is churning away. The hard-disk access light flickers and the drive might make a whirring, whizzing or high-pitched whining noise. If the mechanism in the drive is loud, you definitely know that something is going on!
In the article How Hard Disks Work, you can see that there is an arm that holds the read-write heads. This arm can move the heads to tracks near the hub or near the edge of the disk. A normal hard disk is 5 inches (12.5 cm) or so in diameter. This arm, therefore, can move about 2 inches (5 cm) across the face of the disk.
The speed at which this arm can move is astonishing. The arm is very light, and its actuator is powerful and precise. The arm can slide across the face of the disk hundreds of times per second if it needs to.
If you think about how a speaker works, there is not much of a difference. A speaker is moving a lightweight cone back and forth hundreds of times per second to generate sound. As the hard-disk arm moves back and forth rapidly, it sets up vibrations that our ears hear as sounds.
Why, when you click on a simple spreadsheet file, would the disk's heads have to move so much (20 or 30 seconds worth of movement sometimes)? There are three things that cause all the movement:

• To start a spreadsheet application like Excel, the hard disk has to load the application itself along with a number of DLLs (dynamic link libraries) that support the application. The total size of all these different files might be 10 to 20 megabytes, and the files are scattered all over the disk. Loading 20 megabytes of data takes a lot of time and requires the disk head to move thousands of times to retrieve all the pieces.
• The data file itself has to load. The operating system (OS) has to move the head to the drive's directory to find the folder, make sure the file name exists, and then discover the location of the file. Then the OS may need to read dozens of tracks scattered all over the drive to access the file.
• If the physical RAM is full, then during the loading process the OS will have to unload parts of physical RAM and save them to the paging file on the disk. So while the OS is trying to load the spreadsheet application and all the DLLs and the data file, it is at the same time trying to write millions of bytes of data to the paging file to make room for the new application. The drive head is moving all over the disk to accomplish these intermingled tasks. See this Question of the Day for details.

Altogether, clicking on a single icon may cause 40 or 50 megabytes of data to move between the drive and RAM, with the disk heads repositioning themselves thousands of times in the process. That is why you hear the drive "churning" -- it's doing a lot of work!

If you have a Windows PC, you will sometimes get into a situation where the computer randomly access the floppy disk drive every few minutes -- for no apparent reason! Typically, the harmless annoyance occurs because some program "thinks" it needs to read or write some data to a diskette.
In most cases, there may be a document in your recent history folder (Start >> Documents) that was once on a diskette. Here are the steps to clear the document history file Windows uses:

1. Click Start
2. Click Settings
3. Click Taskbar
4. In the Documents area, click Clear
5. Click OK

Other causes of the problem:

• Microsoft Office's Find Fast utility may be running and trying to index your FDD. Remove it from the Startup group, or in Control Panel, look for Find Fast and disable it from starting. Find Fast installs automatically with Office and can be a resource hog as well!
• The System Agent may be running a task; if present, click the System Agent icon in your System Tray for further information.
• A virus scanner program may be trying to check the drive. Check the setup of your virus scanning software for further information. A diskette scan at startup or shut down may be normal, but a scan between these times is typically a user-controlled option.

Note: If it is the CD-ROM drive that is being accessed for no reason:

1. Click Start
2. Click Settings
3. Click System
4. Click Device Manager
5. Click CD-ROM drive
6. Click Properties
7. Uncheck Auto Insert Notification

In his new book "The Big Switch: Rewiring the World, from Edison to Google," computer industry writer and former executive editor of the Harvard Business Review Nicholas G. Carr discusses the changes he sees in the future of computing. One of the more dramatic changes is a shift to cloud computing -- where applications and files are stored on a large, centralized supercomputer or network. The end user accesses his or her files using computers that are more streamlined but less sophisticated than today's typical machines.

John Todd/Sun Microsystems/Getty Images
Nicholas Carr, seen here at a Sun Network Conference in 2003, believes that tech giants Apple and Google may be on the verge of creating a cloud computer.

On October 17, 2007, Carr took the idea a step further in a posting on his Rough Type blog. He called out two hot technology companies, Google and Apple, and said they were on the verge of a partnership in which Apple would make an inexpensive piece of hardware users could carry around. This would leverage the computing power of the vast data centers Google has been building to hold the applications and the data for millions of users.
The idea of cloud computing certainly isn't new. Oracle's Larry Ellison launched the New Internet Computer (NIC) company in 2000 to lead the industry forward to that goal. The concept is very simple: On your desk, you would have a very low-cost computer with just a processor, a keyboard and a monitor. There would be no hard drive or CD/DVD drive. It would be hooked up to the Internet and would link to a central supercomputer, which would host all of your programs and files. The idea, however, was ahead of its time. The NIC sold very poorly, probably due to a dearth of broadband availability in the United States [source: PCWorld]. The company folded in 2003.
But by 2006, nearly 75 percent of Americans had broadband access at home [source: Neilsen/NetRatings]. Could a Google/Apple team make cloud computing a widespread phenomenon? And if they move forward, what's in it for Google and Apple? The biggest question of all: If they build the cloud computer, will anyone use it?
Read on to learn more about the future of computing.



A googol is the name for a one followed by 100 zeros. Google's name comes from its founders' desire to keep track of the vast amounts of information on the Internet [source: Google]. As the company grew, it began offering more services than just Web searches. Through in-house innovations and acquisitions of other companies, Google created what is now Google Docs, a Web-based suite of applications that includes word processing, a spreadsheet and a presentation program. With Gmail, that puts Google in direct competition with Microsoft for the corporate desktop. And unlike Office, Google Docs is completely free.
These hosted services are the kinds of applications that would be at the core of a cloud computer, just one reason it would be feasible for Google to be the perfect back-end for a hardware manufacturer to partner with. Google's machine, really a network of machines, offers amazing computing power. It also offers redundancy. Google already stores multiple backups of its information on its equipment, and if one part of one machine breaks, it can be swapped out without any loss of information [source: Baker]. Using a cloud computer stored on Google's massive infrastructure would free you from having to take your files with you -- no thumb drives, laptop hard drives, CDs, DVDs or other removable media. You could work on your projects from home, from work and on your mobile computer while on the go.
With a cloud computer, you probably wouldn't have to pay for software. Using applications hosted on the server, your local machine would have all the software it needs to work without having to store it locally. You wouldn't have to update your software to the next version -- and everyone would use the same software on the cloud. There should be no compatibility issues.
But what happens to those frequent flyers who need to work as they travel? A cloud computer would require an Internet connection, and today's airliners don't offer that ability, though some carriers have plans to offer in-flight access. You'd be stuck reading or watching the in-flight movie. You'd also have to be comfortable with letting Google, or whomever else, keep your documents online. Many corporations don't allow their documents past their firewalls. Would these companies change their minds if the majority of business was done on a cloud-computing model?

Craig Mitchelldyer/Getty Images
In 2006, Google built two giant computing centers in The Dalles, Ore. Each is the size of a football field and needs massive amounts of cooling for the computers inside.

One of the biggest problems involved with creating a cloud computer is the amount of electricity required to make it work. Google built its data center in The Dalles, Ore., because of the high-speed Internet access powered by fiber optic lines and the nearby The Dalles Dam [source: Gilder]. Google needs large amounts of electricity to power the cooling equipment necessary to keep thousands of servers running. In fact, the two football-field-sized buildings each have two cooling plants four stories tall [source: Markoff and Hansell].
If Google can't handle the processing power needed to offer the world a computing cloud, it certainly is well on its way to building it. But why would Google partner with Apple for the end-user hardware? Read on for Carr's best guesses and what his critics say.
So why do Carr and others think Google is so interested in creating a cloud-computing network for the masses? It's not such a stretch. Google is now one of the largest computing companies in the world, and it's certainly interested in new technologies and new business opportunities.
Google CEO Eric Schmidt joined Apple's board of directors in August 2006. When asked about the idea of teaming up with Apple in a December 2007 interview with Wired Magazine, Schmidt said it plainly: "Google's architectural model around broadband and services and so forth plays very well to the powerful devices and services Apple is doing. We're a perfect back end to the problems that they're trying to solve" [source: Vogelstein].
According to Carr, Apple doesn't have the kind of supercomputing power that would be required to drive the back end of the partnership. There aren't many organizations that do. Only Google, Yahoo, Microsoft, IBM and Amazon have the ability, says Prabhakar Raghavan, the head of research at Yahoo [source: Baker]. Google and Apple have had a partnership dating back years. If Microsoft succeeds in its bid to acquire Yahoo announced Feb. 1, 2008, the combined companies may well be able to leverage a sophisticated cloud-computing environment.
If Google and Apple do team up for this sort of partnership, here's what Carr feels their cloud computer would be like:

• Inexpensive: The machine you'd buy would be under $200 and there would be no charge for applications or data transfer.
• Green: With a low-power chip and flash memory, an Apple thin client -- a network computer -- would have no power-hungry optical drive or hard drive.
• Easy to maintain: No optical drive or hard drive also means fewer moving parts, which means it would probably live a longer life.
• Easy to update: You wouldn't have to worry about updating your software, that would all be taken care of for you. You could just use your machine until it simply wore out [source: Carr].

In this deal, Carr says, Apple would sell the hardware, and Google would subsidize the cost of supplying the servers with advertising, just as it does in other businesses in which it works. Schmidt said Google would offer as many of its services as it could for free, though the company believes that more advanced users might be asked to pay for access to more features.
Robert X. Cringely, noted technology reporter and columnist, agrees with Carr that a Google-Apple cloud-computing partnership could take place, but he also believes the deal might not be as simple as Carr makes it out to be. Instead, the personality of Apple's iconic CEO and co-founder Steve Jobs might provide a source of irritation for Schmidt and Google. "Schmidt (and Carr) see that Apple doesn't have the supercomputer, but Jobs just as firmly believes that Google doesn't know how to run the supercomputer it has, and besides, he can rent a supercomputer anytime he wants one, so there" [source: Cringely].
Cringely believes that Apple will make Carr's cloud-computing device but will also make other cloud computing devices at a variety of prices. He says that Apple will be the dominant company in the partnership, and Google would take a back seat.
Could Apple really find other partners to supply services to its customers? What if Google and Apple do team up? Will anyone take them on? Learn more about other cloud computing efforts on the next page.
One of the reasons the idea of cloud computing is getting so much traction is the efforts of companies other than Google to make it happen. Microsoft, Amazon and IBM are some of those known to be considering cloud offerings.
Two of the leading candidates to compete with Google or a partnership with Apple may be joining forces. On Feb. 1, 2008, Microsoft announced it had made a bid for Yahoo, which would help both companies in their quest to beat out the search giant [source: Microsoft]. In addition to massive computing power and many other Web services, Yahoo brings a robust Web mail network and photo site Flickr to the table. Meanwhile, Microsoft offers Windows Live, a word processing program and calendar. With its Office suite already entrenched in the desktops of offices across the country, a Microsoft cloud could enter the race as a contender.
Another potential competitor could be Amazon.com. Already one of the world's largest online retailers, the company has interests in other areas as well. Amazon Web Services is a suite of cloud resources aimed at small developers who need a place to work online [source: Amazon.com]. The Amazon Elastic Compute Cloud (EC2) gives users computing power for their work. They can store files in the Amazon Simple Storage Service (S3) and use SimpleDB, a database, to store and access smaller files quickly [source: Claburn].

Forschungszentrum Jülich/IBM
In its Blue Cloud initiative, IBM wants to network its massive computers, like this one at a research center in Jülich, Germany, to create a powerful cloud.

In November 2007, IBM announced its Blue Cloud initiative, offering a package of hardware and software to allow its customers to create their own internal clouds [source: LaMonica]. The company had already partnered with Google to provide cloud solutions for six American universities a month earlier. IBM hopes to grow the program to allow more universities and corporate and government entities to join in [source: Lohr].
Many companies are offering hardware designed to operate on cloud networks, including Hewlett Packard, Dell and Clear Cube. However, you wouldn't necessarily need a computer to access a cloud network -- you could also use other hardware designed to link to the Internet, such as a wireless phone. In January 2008, Google bid in a U.S. government auction for a 700 MHz radio frequency license which would allow them to operate a wireless phone service [source: CNET News.com]. Winning the bid would open the door to Carr's idea just that much farther. Google argued that the frequencies should be accessible by a range of devices, and the company got its wish: The spectrum became open-access once the bidding reached the $4.6 billion reserve price [source: Albanesius].
Despite Carr's enthusiasm -- he said in his blog post he expects the Google-Apple partnership to bear fruit in "months, not years" -- there has been no formal announcement from either company. But in January 2008, Apple announced a new product that's similar to a cloud computer in some respects.
At the MacWorld San Francisco trade show, Apple CEO Steve Jobs unveiled the closest thing it has to a cloud computing device: the MacBook Air. It's less than an inch thick at its largest; Jobs pulled the demonstration model from a manila mailing envelope during the product announcement. It weighs only three pounds. To get it so thin, Apple engineers sacrificed an optical drive and some of its connections, including Ethernet. The battery had to be incorporated in a way that prevents users from replacing it themselves. Unlike a true thin client, the MacBook Air has a hard drive, which can be either a traditional drive or a solid-state drive [source: Apple].
But for now, Google and Apple are not officially partnered on a cloud device -- the MacBook Air is not tied solely to Google for storage and software.