10/10

Definition: An Operating System (OS) is a system software that acts as an intermediary between user programs and computer hardware. Functions: 1. Process Management — creation, scheduling, termination 2. Memory Management — allocation, deallocation, protection 3. File System Management — organization, storage, access control 4. Device Management — I/O device control via drivers 5. Security & Protection — authentication, access control Types: Batch, Time-Sharing, Distributed, Real-Time, Embedded [DIAGRAM: Layered architecture of OS — User → App → OS → Hardware]

[Cue Column] • Stack LIFO? — Last In, First Out • Queue FIFO? — First In, First Out • Push/Pop O(1)? — Amortized • Stack applications? — Expression eval, backtracking [Notes Column] Stack: ADT with push()/pop()/top(). Implemented via array (fixed) or linked list (dynamic). Queue: ADT with enqueue()/dequeue(). Circular queue avoids false overflow. [Recall Questions] 1. Why circular queue over linear? → Memory reuse 2. Stack vs Heap allocation? → Lifetime difference

Unit-wise Weightage (avg/paper): • Unit 1 — OSI & TCP/IP: 12 marks [HIGH] • Unit 2 — Data Link Layer: 14 marks [HIGH] • Unit 3 — Network Layer: 10 marks [MED] • Unit 4 — Transport Layer: 16 marks [HIGH] • Unit 5 — Application Layer: 8 marks [MED] Top Predicted Topics (90%+): 1. TCP 3-way handshake (repeated 4/5 exams) 2. CSMA/CD vs CSMA/CA comparison 3. Congestion control algorithms 4. IPv4 vs IPv6 (new — 2024 pattern)

Q1. Which property ensures that either all operations of a transaction are completed or none? A) Atomicity [✓ Correct] B) Consistency C) Isolation D) Durability [Distractor: B ensures DB state correctness, C ensures concurrency transparency, D ensures persistence — but Atomicity is the all-or-nothing property] Q2. [Bloom's L4 — Analyze] In the log <T1, A, 100, 200>, what does this represent? A) T1 updated A from 100 to 200 B) T1 updated A from 200 to 100 C) T1 deleted A... [✓ A — This is an UNDO-type log record]