Sign in to follow this  
alnite

anybody here familiar with FAT?

Recommended Posts

Anyone here familiar with FAT (File Allocation Table) used by early Operating System, and some devices today? I am trying to figure out how do you find files. Of all articles I ran into on the Internet, none of them speak about how FAT finds its files. Say, I am trying to open C:\foo\zzzzz.txt And say I have 20000 files in my C:\foo\ directory, and zzzzz.txt is the last file. Now it looks like you have to do a linear search because everything is represented in linked list. "Go to directory C:\" -> "sequentally finds foo\" -> "sequentially find files that has name zzzzz.txt" But that doesn't seem to make sense because it'd be terribly inefficient. Do they have a name mapping technique that's not described, or perhaps part of the patented FAT technology?

Share this post


Link to post
Share on other sites
Quote:
anybody here familiar with FAT?

Yes I'd used to have a lot, before I stopped eating fastfood! ;)

Sry couldn't resist.
It's a long time since I fiddled around with FAT, but I once wrote this nifty tool that changed the name entry to some special characters so that DOS couldn't recognize the entry as a valid file.
I.e, I could hide directories from all programs etc.

Quote:
Now it looks like you have to do a linear search because everything is represented in linked list. "Go to directory C:\" -> "sequentally finds foo\" -> "sequentially find files that has name zzzzz.txt"


I think you are correct here, but I also vaguely recall that there was some component that cached the LRU entries (maybe a 64K cache).
But my memory might be off.

Quote:
But that doesn't seem to make sense because it'd be terribly inefficient.

FAT wasn't efficient at all, so that's correct.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this