One of the main jobs of the Operating System is managing how files are physically stored on secondary storage, for example: where and how files are placed on a magentic hard disk drive, and how these files are then displayed to the user.
Most Operating Systems visualise and display the files and directories (folders) to the user as a hieracy, with directories being able to store files and other folders with the initial folder being called the root directory. This hieracy can be displayed as a tree diagram.
When interacting with the Operating System, it will allow the users to carry out different actions on files. These include:
When an Operating System deals with storing files on secondary storage it makes use of blocks and sectors. The secondary storage device (for example: hard disk drive) is broken down into equally sized sectors and when a file is being stored it is broken down into blocks (either the same size of less than the size of a sector). The blocks are given a sequence number then written to the sectors.
The blocks that make up files are not always stored contigiously (stored together), this can be caused by gaps being left by deleted files. This can sometimes cause performance issues on older hard disk drives which benefit from files being store in a contigious or sequential manner.
The operating system keeps track of where the blocks for each file are stored and can be placed back together when needed.