Week 11: File Systems

Question 1

What is a file?

Answer 1

A collection of information managed by the operating system, such as machine code, data, documents, or multimedia.

Question 2

What properties do files have?

Answer 2

Name, type, size, structure, and permissions.

Question 3

What is the purpose of file names?

Answer 3

To provide a symbolic, user-friendly way to access stored information without dealing with hardware details.

Question 4

How do naming conventions differ across systems?

Answer 4

• UNIX: Initially 14 characters, now up to 255.
• MS-DOS: 8-character name + 3-character extension.

Question 5

What are common file structures?

Answer 5

• Unstructured bytes: No fixed format (e.g., UNIX, MS-DOS).
• Fixed-length records: Structured as records, with read/write restricted to whole records.
• Special structures: Database key-index files or Apple Macintosh resource/data forks.

Question 6

What are examples of file types?

Answer 6

Regular files, directories, special files (character/block), and pipes.

Question 7

How do file types differ across systems?

Answer 7

Some enforce types (e.g., .exe in MS-DOS), while others treat types as optional (e.g., .txt in UNIX).

Question 8

What are the two main file access methods?

Answer 8

• Sequential access: Read/write in order (e.g., magnetic tapes).
• Random access: Read/write in any order (e.g., hard disks).

Question 9

What are common file attributes?

Answer 9

Owner, permissions, size, creation/modification/access times, and locking flags.

Question 10

What are some examples of file operations?

Answer 10

• Basic: Create, delete, open, close, read, write.
• Additional: Append, seek, get/set attributes, rename.

Question 11

What is a directory?

Answer 11

A logical grouping of files, often implemented as a special type of file containing metadata about its contents.

Question 12

What is a hierarchical directory system?

Answer 12

A tree-like structure where directories contain subdirectories, starting from a root directory.

Question 13

What are absolute path names?

Answer 13

Paths that start from the root directory (e.g., /usr/local/bin).

Question 14

What are relative path names?

Answer 14

Paths that start from the current working directory (e.g., bin/safecopy).

Question 15

What special entries exist in hierarchical systems?

Answer 15

. refers to the current directory, and .. refers to the parent directory.

Question 16

What are hard links?

Answer 16

A hard link is a directory entry, created with the LINK system call, with a different name, but a pointer to the same disk blocks

Question 17

What are symbolic (soft) links?

Answer 17

A file of a special type which contains the path name (relative or absolute) of the file that is pointed to

Question 18

What are some examples of directory operations?

Answer 18

Basic: Create, delete, open, close, read.
Additional: Rename, link/unlink, file tree walk, get/set attributes, change working directory.