Talk: File Allocation Table
From open-encyclopedia.com - the free encyclopedia.
I removed this
- FAT is a relatively early file system design that was designed in a hurry to replace the CP/M file system - it was in fact the main innovation in the earlier versions of MS-DOS compared to CP/M, otherwise DOS was almost a clone of CP/M. FAT's designers did not even exploit what was already known about file system design, and because of that, it suffered from several problems. First, its simple file layout allows for easy fragmentation, which leads to significant slowdowns during file system operations. Secondly, FAT was not designed for redundancy in the case of system failure. Thirdly, the first versions of FAT allowed file name sizes of only up to 11 characters (file name of 8 and a file extension of 3), although a work-around was developed when Microsoft implemented VFAT, that would allow file names of up to 255 characters. Finally, the large cluster size in many versions of FAT meant that a lot of space was being wasted on padding small files to the cluster size.
- However, because IBM designated MS-DOS as its primary operating system for its PC, and MS-DOS used FAT, FAT became widely used and is still used in a number of circumstances. Because of the primitive design, it is easy to create a basic FAT implementation, and because of the ubiquity of MS-DOS and Windows, FAT has become useful in providing a base level of interoperability in some circumstances.
because overall the tone is not neutral, makes incorrect statements, and is overall not useful. The history below this makes a lot more sense and covers the facts better. And yes I am a coauthor of MSDOS and the FAT32 file system as well; hard to prove identity on internet, anyway you never heard of me so what good would that do. 67.168.183.122
- If you have no way of proving your identity then stop using it as the basis for your edits. Which parts of those paragraphs are non neutral, incorrect or not useful? Was FAT not subject to fragmentation? Was it not used by MS-DOS? Is it not "easy to create a basic FAT implementation"? Outline the parts you disagree with don't just delete the paragraphs wholesome. Also if you registered an account and signed your posts with ~~~~ that would help. AlistairMcMillan 10:45, 21 Sep 2004 (UTC)
gah my explanation was deleted on your last post! anyway, the text is non-neutral with comments such as "designed in a hurry", "main innovation","did not even exploit", et al. All of this is biased and inccorect. Facts are wrong two, such as claiming no redundancy which FAT does indeed have; the concept of fragmentation causing a problem is not that big a problem with the original FAT, and fragmentation exists in all file systems anyway; the reference to cluster size is a red herring and doesnt mean anything really. Basically, these paragraphs provide no useful information but ignorantly sniping at decisions made by engineers many years ago. The history section below the header is sufficient. 67.168.183.122
- Your claim that your explanation was deleted isn't backed up by the edit history of this page. You are aware that all edits are recorded, right? Please explain what redundancy FAT has? Two copies of the FAT table? Is that what you are talking about? Fragmentation is a big problem with FAT filesystems and to my knowledge while other filesystems have fragmentation, no other filesystem has as large a problem with it as FAT. The comment about cluster size needs to be better explained it is too ambiguous as it stands, however it is an issue with FAT filesystems.
- These paragraphs could be a lot better written and do show some bias, but they are not non-factual and would be better re-written, not deleted. AlistairMcMillan 11:00, 21 Sep 2004 (UTC)
- BTW About your VFAT edit. What is a DELFN? When was it introduced? What is the name of the filesystem that introduced it? AlistairMcMillan 11:10, 21 Sep 2004 (UTC)
- IMHO language in those two paragraphs is somewhat biased and overstated. But it is basically factual and deserves rewriting rather than deletion. For example, it would be better to state that the original name of the OS was "QDOS," for "Quick and Dirty OS," and cite the actual timeline of the development, and let the reader decide whether it was "designed in a hurry." I think it's reasonable that if Microsoft had not been in a hurry, they would have written an OS themselves rather than purchasing QDOS from Tim Paterson. The statement "DOS was almost a clone of CP/M" is an exaggeration. IIRC, though, Microsoft has acknowledged that there was some actual "low-level borrowing" (i.e. actual incorporation of binary code) from CP/M in the first release of MS-DOS, in one of the file system APIs. IIRC the use of these API calls was deprecated from the start and the code itself was eventually removed. I certainly wouldn't put any of this in the article until and unless I can find references to back this up, though. I think it is NPOV to say that FAT was technically unsophisticated, in comparison to minicomputer and mainframe OS file systems, at the time it was introduced; that it was derived from CP/M's file system (again, I think Microsoft acknowledges this somewhere, probably in the MS-DOS encyclopedia); and that whether or not it is patentable, it is not regarded within the technical community as being significantly original or innovative. Dpbsmith (talk) 14:36, 21 Sep 2004 (UTC)
67.168.183.122 23:03, 21 Sep 2004 (UTC) Come on guy, go read what you put in there. The whole first new paragraph says not one thing about the FAT file system, but instead defends some position about the history of MSDOS. These statements are not neutral, but actually an attack. I am going to ask you to show some character, and do not put that stuff back in. The history of FAT is discussed in the history section of the article already.
As an aside, please recall that DOS booted in only 16k of RAM, off a 360k floppy, no harddrive, and still had space for programs! [the memory print for a mouse cursor today is larger than all of MSDOS] So it is not constructive to comment how stupid the file system was, or what the features it lacked compared to modern systems. It is impressive for what it did do, not a failure what it did not do!
67.168.183.122 23:03, 21 Sep 2004 (UTC)
What this guy did was to take an existing paragraph that had some POV problems and add some supporting material justifying it from a more neutral point of view. I appreciate what you're saying and am not reverting the change. Nevertheless, in understanding FAT, and, yes, the licensing controversy, I strongly disagree that it was "impressive for that it did do." All of the minicomputer OSes of the day needed to achieve pretty much the same things in comparable amounts of RAM, and most of them managed to do it better than the comparable microcomputer OSes did. The Apple DOS 3.3 file system was worse that FAT, of course. Just as with literary articles, I think it is entirely appropriate that computer articles include justified, neutral, well-backed critical appraisals of the technology along with descriptions of the technology itself.
I'm not sure how much of this really does belong in the article or where it should go, but I'm not convinced that it should be removed entirely. Therefore, I'm putting it here. This is the material that was removed.
- FAT is a relatively unsophisticated file system design. Tim Paterson, the original developer, has written that "The first versions of the operating system, called QDOS 0.10, were shipped in August 1980. QDOS stood for Quick and Dirty Operating System because it was thrown together in such a hurry (two man-months)." Microsoft purchased the rights and released the system as MS-DOS in July 1981. FAT was a replacement for the CP/M file system—it was in fact the main innovation in the earlier versions of MS-DOS compared to CP/M. In his book Accidental Empires, Robert X. Cringely characterized QDOS as "a 16 bit clone of CP/M... Paterson admitted to a little "low-level" borrowing from CP/M, too, but claimed that most of the code was his own. Gary Kildall still thinks a lot of QDOS code was stolen straight from his CP/M."
- FAT's designers did not even exploit what was already known about file system design, and because of that, it suffered from several problems. First, its simple file layout allows for easy fragmentation, which leads to significant slowdowns during file system operations. Secondly, FAT was not designed for redundancy in the case of system failure. Thirdly, the first versions of FAT allowed file name sizes of only up to 11 characters (file name of 8 and a file extension of 3), although a work-around was developed when Microsoft implemented VFAT, that would allow file names of up to 255 characters. Finally, the large cluster size in many versions of FAT meant that a lot of space was being wasted on padding small files to the cluster size.
I'm confused about the naming of the FAT versions.
Isn't the number after FAT just the size of the FAT entries? VFAT can be used with FAT12, FAT16 or FAT32 but aren't they basically all the same?
-->>VFAT is simply the name of a driver in Windows, the article was incorrect when it associated that with a particular file system layout. I have removed that line. 67.168.183.122
FAT12 uses 12-bit entries, while FAT16 uses 16-bit entries. FAT32 indeed uses 32-bit entries, but is also a redesign, and is incompatible with prior versions.
There is MUCH that could be added here. How much detail is wanted? --Scott. 08:02, 2004 Feb 9 (UTC)
moved from the article — I don't feel like inocorporating this right now.
[[Note added 18 April 2004:--
Most of this patent stuff is non-neutral, incorrect, and badly sourced (slashdot?). It should probably be removed as a larger portion of the text talks about some opensource view on patents which really has nothing to do with FAT[] : 67.168.183.122
The patent datings quoted above are unfortunately not the correct/relevant ones for prior art purposes, for three of the four MS patents.
USP 5579517, although filed on Apr 24 1995, was based on a "continuation of U.S. patent application Ser. No. 08/041,497, filed Apr. 1, 1993, now abandoned." Thus, its effective filing date was April 1, 1993.
The timeframes of citable prior art for this patent are:
(1) for printed publications or technology in public use in USA:-- -- more than 12 months before the effective filing date (i.e. <=March 31, 1992), or -- before the MS technology was invented (if that occurred less than 12 months before the effective filing date), or
(2) for prior inventions invented in the USA, but not disclosed in printed publication or put in public use before the dates already mentioned:-- -- before the MS technology was invented (whenever that occurred).
USP 5758352 has the same effective filing date as 5579517, i.e. April 1 1993, and the timeframes of citable prior art are the same, too.
USP 6286013 was based on an application which was a "continuation of U.S. patent application Ser. No. 08/356,010, filed Dec. 13, 1994, now abandoned, which was a continuation-in-part of U.S. patent application Ser. No. 08/041,497, filed Apr. 1, 1993, now abandoned."
That means the claims here might have either one of two effective filing dates, either April 1 1993 (for claims that entirely reflect the content of the application filed on that date, shown here by the published content of 5579517), or else Dec 13, 1994, (for claims that are not completely referable to the content of the 1993 application/5579517, but depend on content that was first added to the 1994 application).
In each case, the time-frames of citable prior art are set by the applicable filing date in the same way as noted above.
(One of the keys to this complex scheme mandated by law is that a 'continuation' application copies the content of its 'parent', so all of its content normally benefits from the parent filing date, while a 'continuation-in-part' application partly shares content but partly adds new content, compared with its 'parent', and the effective filing dates are allocated accordingly. For the other complications of defining the timeframes, see 35 USC 102, specially parts (a), (b), (e), and (g).)
End of note added 18 April 2004.]]
fat and hard disk partitions
i believe dos 2.x could not address up to 32 mb but only 10 mb officially and 15 mb unofficially.
but fairly sure it could from dos 3.x onwards.
did the fat change then ?
- I've changed the first para of the history section. The initial version of MS-Dos didn't support directories, but MS-Dos 2.x and 3.x did while still using Fat12 as the filesystem. Perhaps some change was made to Fat12 for MS-Dos 2.
- Also, the filesystem size limit for Fat12 is 32 MB. 12 bits for each FAT entry which can distinguish 4096 different clusters. It may be that MS-Dos 1 only used a 512 byte cluster size, but later versions of MS-Dos support cluster sizes up to 8 kb. It's possible that dos 2.x supported something in between, so the comment above this might be correct. There were also variants of MS-Dos 3.x which supported disk partitions larger than 32 MB. I'm not sure whether they did this by increasing the cluster size further. Fat16 allowed larger cluster sizes but wasn't introduced until MS-Dos 4. -gadfium 23:50, 6 Dec 2004 (UTC)
- Is it true that FAT originally had only a flat directory hierarchy, and only later were nested subdirectories supported? If true this distinction should be noted. --Bk0 03:23, 7 Dec 2004 (UTC)
- The first version of MS-Dos, ie version 1, did not support subdirectories (and no version of MS-Dos supported the CP/M equivalent of user areas). The concept of subdirectories was well established by that time (eg in Unix), but perhaps they weren't considered necessary for such small machines. Although I've been involved with computers for a very long time, I've never actually seen version 1 of MS-Dos running. I presume that MS-Dos 1 supported some file attributes (which include read-only, hidden, system, archive in later versions), so an unused attribute bit was used for directories in MS-Dos 2 and later. Long file names use a previously-ignored combination of attribute bits which allow them to co-exist with 8.3 file names.-gadfium 04:37, 7 Dec 2004 (UTC)
FAT12 vs. FAT16
Just yesterday, I bought a consumer mp3 player that does not support FAT16, but only supports FAT12 with long file names. I think it interesting that FAT12 is still being used today; MMC cards are formatted, by default, with the FAT12 filesystem (according to one online discussion) because many older digital cameras and what not only support FAT12. I'd like to add this information to this article, but am not sure how to do so. Samboy 03:49, 7 Dec 2004 (UTC)
