Chapter 6.1 Lock-in

ACompressed recap

File = attributes + operations; per-process table holds the file pointer, system-wide table the open count. Access: sequential, direct, indexed. Directories: tree with absolute/relative paths; hard link = same inode (link count), soft link = path. rwx bits r4 w2 x1. Allocation: contiguous (start + b), linked (b + 1 reads; FAT one entry per block), indexed/inode (direct + k + k² + k³) × B with k = B/P. Bitmap = blocks/8 bytes.

BMerged rule card

6.1.1 Files, directories and access methods

• File: attributes + operations; open() returns a descriptor; seek moves the pointer.
• System-wide table (open count) + per-process table (file pointer).
• Access: sequential, direct, indexed. Directories: single, two-level, tree (absolute/relative paths), acyclic graph, general graph.
• Hard link = same inode, link count; soft link = path (can dangle).
• UNIX rwx bits: owner/group/others, r4 w2 x1 (e.g. 754 = rwxr-xr--).

6.1.2 Allocation methods: contiguous, linked (FAT), indexed (inodes); free space

• Contiguous: (start, length), block b = start + b; external fragmentation.
• Linked: next pointers; block b needs b + 1 reads. FAT = one entry per disk block, cached.
• Indexed/inode: k = B/P; max size = (direct + k + k² + k³) × B; reads: direct 1, single 2, double 3, triple 4.
• Free space: bitmap (blocks/8 bytes), linked list, grouping, counting.

CInterleaved GATE-style questions

Q1 · NAT · 1 mark(s) — Permissions

Octal value of r-xr-xr-x?

Numerical answer: ________

Q2 · MCQ · 1 mark(s) — Soft link

A symbolic link's target is deleted. The link:

1. (A) becomes dangling: opening it fails
2. (B) is deleted automatically
3. (C) becomes a hard link
4. (D) still opens the old data

Q3 · MCQ · 1 mark(s) — Directories

In a tree-structured directory, a relative path starts from:

1. (A) the root
2. (B) the current working directory
3. (C) the user's home directory always
4. (D) the disk's first block

Q4 · NAT · 2 mark(s) — Inode

Inode with 10 direct, 1 single and 1 double indirect pointer; block 2 KB; pointer 4 bytes. Maximum file size in MB (2 decimals)?

Numerical answer: ________

Q5 · NAT · 1 mark(s) — Linked

Linked allocation (no FAT): how many disk reads to reach block 49 of a file (blocks numbered from 0)?

Numerical answer: ________

Q6 · NAT · 1 mark(s) — Contiguous

A contiguous file starts at block 1200. Which disk block holds file block 35?

Numerical answer: ________

Q7 · NAT · 2 mark(s) — Bitmap

A 64 GB disk has 8 KB blocks. Free-space bitmap size in KB?

Numerical answer: ________

Q8 · MCQ · 1 mark(s) — FAT

A FAT has one entry for each:

1. (A) file
2. (B) directory
3. (C) disk block
4. (D) inode