FILE ATTRIBUTES

FILE:

• A file is a named collection of related information that is recorded on secondary storage, usually as a sequence of bytes, with two views:
  • Logical (programmer) view, as the users see it (how they are used and what properties they have.).
  • Physical (OS) view, as it actually resides on secondary storage.
• The information in a file is defined by its creator. Commonly, files represent programs (both source and object forms) and data.
  • Data files may be numeric, alphabetic, alphanumeric, or binary.
  • Files may be free form, such as text files, or may be formatted rigidly.
• A file has a certain defined structure, which depends on its type.
  • A text file is a sequence of characters organized into lines (and possibly pages).
  • A source file is a sequence of subroutines and functions, each of which is further organized as declarations followed by executable statements.
  • An object file is a sequence of bytes organized into blocks understandable by the system's linker.
  • An executable file is a series of code sections that the loader can bring into memory and execute.

FILE ATTRIBUTES:

• A file's attributes vary from one OS to another but typically consist of these:
  • Name.
  • Identifier. This unique tag, usually a number, identifies the file within the file system; it is the non-human-readable name for the file.
  • Type.
  • Location. This information is a pointer to a device and to the location of the file on that device.
  • Size. The current size of the file (in bytes, words, or blocks) and possibly the maximum allowed size are included in this attribute.
  • Protection. Access-control information determines who can do reading, writing, executing, and so on.
  • Time, date, and user identification. This information may be kept for creation, last modification, and last use.