Practice Question

Duration: 4 min

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Inside: a video lesson and guided study material.

Module outline

  1. Quantitative Aptitude: Number System, Percentage, Profit and Loss, Ratio and Proportion (Ratios), Average, Time and Work, Speed Time and Distance, Simple Interest and Compound Interest, Mixture and Alligation, Data Interpretation, Permutation and Combination, Probability, Logarithm, Powers and Exponents (Surds and Indices), Age Problems, Divisibility Rules, Partnership, HCF LCM, Algebra, Pipe and Cistern
  2. Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Analogy, Coding Decoding, Blood Relations, Directions (Direction Test), Syllogisms, Logical Sequence Of Words, Data Sufficiency, Seating Arrangements, Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Data Arrangement
  3. English Language: Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Vocabulary, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Active Passive Voice (Voice), Direct and Indirect Speech, Cloze Test (Cloze Passage), Tenses, Subject Verb Agreement (Verb Noun Agreement), Preposition, Articles, Conjunction, Adverb
  4. Written English Test: English Writing Ability
  5. Coding: Coding Questions by Yash Sir, C Programming by Yash Sir, Programming in C++, Java, Python for Placements by Yash Sir
  6. Communication Round: Communication Assessment
  7. DBMS (Technical Interview): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Big Data Systems, NoSQL, Data Warehousing & Mining
  8. SQL (Technical Interview): SQL
  9. Operating Systems (Technical Interview): Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  10. Computer Networks (Technical Interview): Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security, Mobile Technology, Cloud Computing and IoT, Cyber and Info Security
  11. OOPs (Technical Interview): Object Oriented Programming (OOPS)
  12. HR Interview: MR & HR Interview Preparation
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video presents a solved example of the C-SCAN disk scheduling algorithm. The instructor analyzes a specific scenario where the disk head is at track 45, moving positively, with a queue of requests: 40, 67, 11, 240, 87. The goal is to determine the service order and total seek distance. The instructor explains that C-SCAN moves the head to the end of the disk, jumps to the beginning, and continues in the same direction. He calculates the total distance by summing the movement from the current position to the end, the jump to the start, and the movement to the final request.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor reads the problem statement visible on the screen: "Consider the situation in which the disk read/write head is currently located at track 45 (of tracks 0-255) and moving in the positive direction." He lists the track requests: 40, 67, 11, 240, 87. He identifies the algorithm as C-SCAN. He explains the movement: the head moves in the positive direction, servicing requests 67, 87, and 240. He notes that it must reach the end of the disk, track 255. He begins the calculation by finding the distance from the current position (45) to the end (255), writing "255 - 45 = 210" on the board. He emphasizes that C-SCAN goes to the end of the disk, unlike C-LOOK which stops at the last request.

  2. 2:00 – 4:10 02:00-04:10

    The instructor completes the calculation for the total seek distance. He explains that after reaching track 255, the head jumps to track 0. He writes "255" to represent this jump distance (from 255 to 0). Then, the head services the remaining requests (11, 40) moving positively from 0. The last request serviced is 40. He calculates the distance from 0 to 40 as 40. He sums the three components: 210 (45 to 255) + 255 (255 to 0) + 40 (0 to 40) = 505. He writes "505" and circles it, selecting option (C). He briefly contrasts this with C-LOOK, drawing a diagram where the head goes to 240 then jumps to 11, but confirms the question asks for C-SCAN.

The lesson effectively demonstrates the application of the C-SCAN algorithm to a disk scheduling problem. By breaking down the movement into three distinct phases—moving to the disk end, jumping to the start, and servicing remaining requests—the instructor clarifies how to calculate the total seek distance. The key takeaway is that C-SCAN treats the disk as a circular list but services requests linearly from one end to the other, ensuring a jump from the maximum track to the minimum track.

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