How Does Hard Disk Work?????????

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!
Hard Disk Basics
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.

Cassette Tape vs. Hard Disk
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.


Capacity and Performance
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.

Storing the Data
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,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.

Microsoft lifts the curtain on Vista Ultimate Extras

For months know, Microsoft has made it known that it planned to position its downloadable Vista Ultimate Extra add-ons as icing on the top tier of the Vista cake. What Microsoft hadn't made public — until January 7 — was exactly what would be part of the Ultimate line up.



But at the Consumer Electronics Show (CES) 2007 kick-off keynote by Bill Gates on Sunday night, Microsoft showed a bit of what Microsoft has planned for the first wave of Ultimate Extras. And at Microsoft's Windows Vista Lab, an event for about 60 bloggers, Most Valuable Professionals (MVPs) and Windows community members held in Las Vegas on January 6 and 7, Microsoft officials filled out details on the rest of its Extras strategy.



Microsoft plans to make available only to Ultimate customers starting on January 30 — the day that that Vista becomes available in the retail channels — the following Extra downloadables:



* A Vista-customized version of the Texas Hold 'Em poker game



* Multi-user interface language (MUIL) packs, designed to allow individuals fluent in different languages to share the same PC. Microsoft plans to make MUILs available for 35 languages, in addition to English. (MUILs also are available to Vista Enterprise customers.)



* BitLocker Online Secure Key Storage. Ultimate customers will be offered a secure place to store their BitLocker encryption keys in the Online Vista Marketplace. That way, if they lose their keys, they will be able to retrieve them over the Web. (BitLocker encryption is a feature of the Ultimate and Vista Enterprise SKUs only.)



* Windows DreamScene, animated wallpaper technology that allows users to run high-resolution video inside the Vista Aero Glass user interface. Microsoft and selected partners, starting with Stardock Corp., will be providing sample content. DreamScene has been known by the codenames "Motion Desktop," and, more recently "Borealis."



* "Digital publications," a bunch of tips and tricks, blog links and other resources for getting the most out of Ultimate. These are just the first few offerings under the Ultimate Extras banner. Microsoft is planning to roll out downloadables over time, company officials said.



Justin Hutchinson, a group product manager for Vista, showed off during Gates' keynote a bit of the capabilities of DreamScene. He also put through its paces a new a "photo-imaging" Extra developed by Microsoft Research. GroupShot allows users to combine elements of multiple pictures together into a new image.



At the Vista Lab, Microsoft officials said that GroupShot. is an example of the kinds of next-generation Extras that Microsoft has in the development pipeline and won't be available as part of the first round of Ultimate Extra downloads. Microsoft isn't going public yet with its packaging or delivery time frame for the next wave of Extras.

 

Trends That Will Impact Your Life In 2007

It is having such a major impact on your lives that we often end up using its power without even realizing that we've done so. You buy a cell phone and later discover that calling and Smsing are two just basic uses of mobile other then these functions you can use mobile to listen to music , click photos, maintain schedules, remember importan dates ,etc . Similarly when you buy a broadband net connection and discover that internet surfing and email are just a small part of what you can do on internet . You can blog , stream live videos or run applications or even access your office work from home . If you lose your internet conection then you are literally cut off from the entire world .

So security would have a new meaning , and will require technology that will secure your digital identity. Connectivity have to be seamless and provide ample bandwidth to let you enjoy all services that are available these days . Likewise there are other areas that can have a lot of impact on your life . CPUs , operating systems , graphics are all undergoing a radical changes which will have tremendous inpact on our lives.