I am making a iOS app where the size of some files is diplayed in MB. My question is if it is correct to calculate 1000 byte = 1kb or 1024 byte = 1kb ? I have seen that Finder on the mac calculates with 1000b, but an iOS file manager called iFile calculates with 1024b. The wikipedia article didn't really answer my question. I am just askig speifically for file size not HD capacity etc.
My question is if it is correct to calculate 1000 byte = 1kb or 1024 byte = 1kb ?
Both are correct, and both are used in different situations.
1024 is more common for file sizes, while 1000 is more common for physical disk sizes, but neither is always used that way. As you mentioned, some programs uses 1000 for file sizes, and for memory cards 1024 is often used rather than 1000.
An example of how inconsistently the units are used is the 1.44 MB floppy disk. It's neither 1.44 * 1000 * 1000 bytes nor 1.44 * 1024 * 1024 bytes, but actually 1.44 * 1000 * 1024 bytes.
An effort was made to introduce the kibibyte unit, which is always 1024 bytes. It never was a hit, but you can see it used sometimes.