File types
  Regular - just data. Interpreted by program accessing it.

  Directory - lists inodes of available files and associated names.

  Symbolic - file containing the path of another file.

  Character special - direct communication with byte unit devices.
    keyboard, serial port.

  Block special - direct communication block unit devices. Raw
    communication with hard drive (boot sequence).

  Pipe - temporary file used to pass data between running processes.
    If 2nd process slower than 1st, output needs to be buffered.
  
  Sockets - similar to pipes, used with parallel processing, networking.