i buy a 1Gb pendrive,but when i check it back,its space only 976MB..
not only mind but all my friend be like that...
why....?
Some space is already reserved for backup and other stuff. I've got similar trouble and visited service center, where got all information.
reserved for backup and other stuff for what?
pen drive has driver software and is installed automatically when plug in to usb port, that software is also stored but we cannot see it, and some other driver files are present in that so we cannot get full space.
It might be to do with the above, but I rather suspect that it's due to the formatting.
On your computer, Windows (or Mac or Linux or any OS) recognises 1Gb as 1024Mb, 1Mb as 1024Kb and 1Kb as 1024b. Most hard drives / mp3 players / flash memory devices are quoted as 1Gb being 1000Mb, 1Mb as 1000Kb and 1Kb as 1000b.
Therefore, the "1 Gigabyte" of your flash drive is actually 1,000,000,000 bytes. Divide this by 1024*1024 gives you 953.7 "real" megabytes.
Hope this explanation helps. 
also, when formatting a disk, a certain amount of space is lost....this is true for all drives HD or flash based...
its more significant on larger drives...my 250GB hard drive for example has only 236GB availabel for use after formatting
emmm...but i never format my pendrive and after i bought it,i checked it at home and it showed 976MB until now,and after i formated it,it still show 976MB..
yahh its true ,myn also same thing
some space is kept for back-up and some for the driver
some pendrives have extra software for security purpose which u can activate using the cd.
Well, actually, the reason is mainly due to what Animal said. For example, 128 MB would appear as 117 MB. Plus, as many said, some of the space is lost for backups and the driver. As for formatting, since it's only 1 GB, the amount of space lost is very much (if at all).
1 GB = 1024 MB
but most of the vendors insist that 1 GB should be considered as 1000MB and not 1024MB
There are several descripancies that occur due to this especially for HDDs.
In case of a pendrive also same is true. 24 MBs are lost because manufacturers definition of 1GB is not same as yours.
But it is a bit difficult to address 1000MB of memory if you reduce it to 976 many addressing problems get solved and drive becomes more efficient.
So no space is lost due to driver and all but its because your so called 1Gb pen drive is not actually 1Gb pen drive
The question is if we are thinking about base 2 or base 10.
1GigaByte is 2^10 what is 1024
but if we say just Giga, that means 10^9 what is 1000
We are really talking about base 2 but, it's more commercial and cheap for them saying it's base 10.
I think some space are reserved for the drive's firmware and driver. Just like any other hard disk or wadever storage media, you don't usually get the full storage space they stated. Like for my hard drive, it states an 80GB hard disk, but I think onli 75GB is available for use.