What Is A File?

Computer people talk about “open this file” “use that file” and so on and so forth and I bet that you have wondered at some point what exactly a file is. You know what a word document is, you know what an email is, but you don’t know what they are representative of: a file on your computer.

A file is a container for data

A file consists of a beginning marker and an ending marker that marks off a collection of data on your hard drive. As an example, imagine if you took a handful of sand and let it out across a table in a solid line. What you would end up with is a constant stream of sand going all the way across the table… right? How could you differentiate any of the sand from the rest of the sand? Now say you took your finger and rubbed it through the sand at two points. Everything inside those two markers could always be differentiated from everything outside of those two markers. That is what a file is on your hard drive.

Files are kept on the FAT (File allocation Table).

Yeah, don’t bother making any jokes about the FAT they have all been made already =P. The FAT works like a table of contents or an index. It is often at the very beginning of your hard drive (yes, your hard drive has a beginning and an end.) It contains an index of the beginning and end of every file on your hard drive. Instead of the files keeping themselves separated on the hard drive the drive just writes data in one continuous string, but then it writes a pointer to the FAT which tells it where the beginning and end of a specific file is. The speed boosts to looking up files is greatly increased (as you could guess if you have ever used an index in a book before) the problem is that if the index gets fried somehow, then the entire contents of the drive will become a mystery to the computer! It is a one way trip to a toasted computer.

This is an act of god style incident which destroys hard drives on occasion. That is why it is important to back up!

So now you know what a “file” is

Files come in different formats. A word document is a specific format which defines how a file is written. But I will explain that another time. For now just remember that a file on your computer is basically a “beginning” and an “end” marker for a section of data written to your hard drive.

God Bless,
-Daniel Kolansky