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File attributes; levels of directories

Short answer

File attributes are metadata such as name, identifier, type, location, size, protection, and timestamps. Directory levels include single-level (name conflicts), two-level (per-user directory but no user grouping), tree-structured (hierarchical, grouping, absolute/relative paths, per-directory protection), acyclic-graph with links for sharing, and general graph allowing cycles.

What are file attributes? Explain about levels of directories.

File attributes

A file is a named collection of related information stored on secondary storage; it is the logical unit of storage seen by the user (programs, documents, data). Files have an internal structure (byte stream, records, tree) and a type (regular, directory, special).

File attributes (metadata) maintained for each file:

AttributeMeaning
NameHuman-readable identifier
IdentifierUnique tag (i-node number) used by the system
TypeText, executable, directory, etc.
LocationPointer to the device and disk blocks
SizeCurrent size in bytes/blocks
ProtectionPermissions: read, write, execute for owner, group, others
Time, date, user IDCreation, last access and modification, owner
FlagsRead-only, hidden, system, archive, lock flags

Levels of directories

A directory is a file containing the entries of other files. Directory structures:

1. Single-level directory: one directory for all users' files.

 root --> [ a ][ b ][ c ][ d ] ...

Simple, but every file name must be unique, no grouping, slow search when many files, and no privacy among users.

2. Two-level directory: a master file directory (MFD) lists the users; each user has a private user file directory (UFD).

 MFD --> user1 --> [a][b]
     --> user2 --> [a][c]

Different users may use the same file names, and search is efficient; but users cannot group their own files and sharing is difficult (needs path names like /user1/a).

3. Hierarchical (tree-structured) directory: directories can contain files and sub-directories to any depth, with a root.

            root
          /   |   \
       bin   usr   home
              |     |
            local   ram
                    / \
                 docs  src

Supports grouping, absolute and relative path names, a current working directory, and per-directory protection. This is used in UNIX and Windows.

4. Acyclic-graph directory: allows sharing of files and sub-directories through links (hard/symbolic), but needs care to avoid dangling pointers and cycles.

5. General graph directory: allows cycles, which need garbage collection or cycle checks.

✓ Answer checked by Claude Opus 5.5 (high effort)

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