The types of file under Unix may be regular directory character special block special Regular files are binary or Ascii files, and contain compiled programs, data files, source code, text, etc. Character special files are devices at a fixed location, with volatile contents. Reads from such files are actually reads from the device. No random access is available on such files.
Examples are keyboard, mouse etc.
In a contiguous layout, the entire file is laid out as one sequence of disk blocks. It is easy to keep track of the file, because you only need its starting block and size. It means that space must be pre-allocated for the file before writing it can take place. In a linked list layout, the file is divided into blocks and part of each block is a pointer to the next block. Keeping track of each file is also easy, because you only need the start of each list.