Don't Panic !!!

That's when things can get really messed up! The more important your data, the slower you should proceed. Please consider:

• All storage devices (disk drives, flash cards, etc.) are structurally simple: they store data in sectors (usually 512 bytes per sector) starting from sector 0, then 1, 2... up to the last sector. Each sector can be written and read independently and is referred to (addressed) by its sequential number.
• As computer users, we tend to write and read files (system, applications, documents, etc.) of various sizes, group them in folders (directories), add to them, erase them, move them around, etc.
• To reconcile these two requirements, there has to be some sort of structure (the directory) that keeps track of which physical sector on the disk belongs to which file and in what sequence.
• The directory is maintained by a branch of the operating system (Windows, MacOS, Unix) called the File System. There are various types of directories (FAT, NTFS, HFS, etc.) and they all do roughly the same job (as above).