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  1. What does the computer do when we format our hard disk or flash disk.
  2. If formatting clears all data on a disk, what is the difference between deleting all files in the disk and formatting the entire disk?
  3. Is it bad to format multiple times?
  4. How many times can a disk be formatted?
  5. Will formatting reduce the lifespan of my drive?
  6. What is the difference between quick formatting and standard formatting?
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1) What does the computer do when we format our hard-disk or Pen-drive.
2) Formatting clears all Data on a Disk , then what is the difference between deleting all files in the disk and Formatting the entire disk

Before answering this, you should know how a file system is built. A file system is a kind of library in which we have books that represent files. These books can be found using the Library's catalogue, telling you in which shelf the books are stacked.

Over time, the catalogue will still contain books that are no longer present in the library or books will be in the library that are not recorded in the catalogue. There will be decay in the system and errors might occur. Also the library might decay and fall into ruin.

When we delete all files from a media, we clear out the entire catalogue but leave all the books in the shelves. When we want to add a file (book), we make room for the new book by removing some of the other old books from the shelf and putting the new book there.

However, if we format the media, we demolish the entire library and rebuild it. The books may then still be recovered from all the rubble of the old library, but once the new library is getting filled up, that books will decay.

3) Is it Bad to format Multiple times
4) On an average how many times can you format your disk
5) Will Formatting reduce hard-disk lifespan

There's no real reason to format several times. Media, as well as hard drives and especially USB thumb drives have a number of write cycles in which according to the manufacturer, proper operation is guaranteed. Formatting media will contribute to the number of write cycles being done. Yet, you won't actually damage the drive.

6) What is the difference between quick Formatting and the standard Formatting

From Wikipedia:

High-level formatting is the process of setting up an empty file system on the disk and installing a boot sector. This alone takes little time, and is sometimes referred to as a "quick format".

In addition, the entire disk may optionally be scanned for defects, which takes considerably longer, up to several hours on larger hard disks.

  • Nice analogy, but wouldn't normal format be equivalent of destroying library's catalog and saying that all space occupied by old books may now be used for something else? – AndrejaKo Aug 30 '10 at 18:30
  • @Andre Have you ever seen books/shelves survive being in a building being demolished? :P – BloodPhilia Aug 30 '10 at 18:31
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    Yes, I've seen bombed, shelled and bulldozed buildings where books and shelves have survived. Of course, the important point is that after format data isn't destroyed, it's just inaccessible and may be recovered unless it is actually overwritten. What you explained is more like zero-filling on modern or low level format on ancient hard drives. – AndrejaKo Aug 30 '10 at 18:39
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    @Andre I edited that part with the demolishing a bit... This better? =) – BloodPhilia Aug 30 '10 at 18:43
  • @BloodPhilia Are you sure that deleting files from a USB drive just deletes them from the catalogue and not wipe them? Thanks for the answer. – Nikos Jan 23 '18 at 19:22
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  1. Essentially, the system just loses the references to any actual information that is on the disk, it doesn't actually 'remove' the information. "Formatting a hard disk drive will overwrite the data on the drive. However, the data hasn't exactly been erased. The formatting process only removes the operating system's ability to read the data on the drive. Data needs to be rewritten to the drive and then reformatted again to ensure that data is no longer accessible." Source

  2. Formatting will typically remove the operating system as well.

  3. Not really. Doesn't really matter.
  4. As often as you'd like.
  5. No. Source
  6. Standard formatting checks for bad sectors on the hard drive and flags them, as well as deletes the references to the information on the hard drive, while a quick format simply deletes the references to the information on the hard drive. Source
  • Hi! Nice answer, but second list should start form number 2. – AndrejaKo Aug 30 '10 at 18:26
  • Thanks! Yeah, adding in a quote messed it up. I'm currently attempting to fix it. – Ryan Aug 30 '10 at 18:28
  • #2 -- the operating system is part of "all files" too – grawity Aug 31 '10 at 9:21
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  1. it initializes an empty filesystem on the device you're formatting
  2. formatting actually clears che "index" that lets you access your data (that's the filesystem), it does not erase actual data blocks around the disk. That's why formatting a device does not take different times if it was empty or full.
  3. it's useless, not bad
  4. if you just "format" and do not write anything else, you could probably do that hundreths of thousand times on flash devices, and some million times on magnetic devices (harddisks). Every sector in every device can be written a number of times, that's millions for hard disks and hundreds of thousands on flash devices. But you don't access physical sectors on flash devices, the controller will do write leveling. And on magnetic hard disk you have spare sectors that will be used to remap bad ones. It's a long story.
  5. yes, but by a really little fraction. Writing many gigabytes (like a dvd iso) on the same disk will probably have a worse effect (the filesystem itself is smaller)
  6. that's a bad naming coming from MS-DOS times. a "quick format" is what we call formatting the device. a "long format" (the one that takes hours to complete) is a formatting + a complete surface scan of the device (they're two totally unrelated things)

EDIT: keep in mind that you cannot actually "erase" anything on hard disks or flash medias. You can just write different, possibly meaningful, data in a sector (like writing a bunch of zeros or stuff like that) but there is no such thing as a physically "empty" sector.

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First you need to know a filesystem is a method of storing and organizing computer files and their data. Essentially, it organizes these files into a database for the storage, organization, manipulation, and retrieval by the computer's operating system.

To format a drive you are creating a new filesystem. You are not only deleting all the files but also deleting the structure that your computer uses to know where the files are.

A quick format is very much like deleting all the files, because your only actually deleting the first little bit of each file. Enough so that your computer now thinks of those files as "free space", even though the original data is there, the computer knows it can write over it at any time. A quick format also creates a new filesystem (but your probably using the same type of filesystem that you were before). A standard Format writes over the whole disk so that the original data isn't there anymore. This takes longer and isn't really necessary.

That should answer 1 and 2 and 6.

(3) No.

(4) There is no limit. Thousands. Less on a Pen-drive, but formating is no different than other writing on the drive. Any writing shortens the lifespan since, especially pen-drives, can only do so much writing before they die.

(5) No, not more than regular writing

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Formatting a drive removes the reference pointer (index) to the files, which were reserved space. The process is the same when you delete a file. It is still present until another file is added to the drive, which then overwrites the previous file's allocated space that is no longer reserved. If your goal is to delete the data on the drive to an unrecoverable state then perform random write followed by zero write operations. To truly be sure data is unrecoverable then either follow the DoD standard of at least seven overwrites or physically destroy the drive's platters (HDD) or primary storage chips (SSD/USB).

If you simply format the drive and then add a new operating system then the majority of its content will remain. The new operating system will be placed in the same place as the previous one unless the user specifies otherwise but this does not occur by default and if done can still leave valuable information that existed in the previous operating systems allocated space.

In summary, formatting merely makes all space available for new information and is obviously necessary as certain devices require/operate more efficiently with different file systems and block sizes. In short, formatting is the easy button for unreserving space. You can format as many times as you'd like and the result is the same. Now making data unrecoverable will wear the drive (both HDD and SSD) as data is physically written to the drive to overwrite previous data. Do not perform these types of write operations to SSDs as it will wear the device sooner and the way many SSDs work when a file is deleted or a drive is formatted makes the process overkill but it can still be done if desired.

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