Practice Question

Duration: 4 min

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Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. General Aptitude & Reasoning: Number System, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Speed Time and Distance, Mixture and Alligation, Data Interpretation, Algebra, Probability, Permutation and Combination, Venn Diagram, HCF LCM, Divisibility Rules, Age Problems, Pipe and Cistern, Partnership, Linear Algebra, Sequence and Series (Series), Statistics, Powers and Exponents (Surds and Indices), Arithmetic, Mensuration and Geometry, Calculus, Trigonometry, Vectors, Speed Mathematics and Basic Mathematics, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Analogy, Series (Number and Letter Series) (Numerical Relations and Reasoning), Puzzle Solving (Puzzles), Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Calendar, Seating Arrangements, Coding Decoding, Blood Relations, Directions (Direction Test), Clock, Analytical Reasoning (Counting Figures Reasoning), Ranking, Order and Sequence, Logical Sequence Of Words, Inequality, Data Sufficiency, Cubes & Dices
  3. Computer Networks & Cybersecurity: 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
  4. Programming, Data Structures & Algorithms: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  5. AI, Machine Learning, Big Data & Cloud: Emerging Tech Trends, Artificial Intelligence, Big Data Systems, Approaches to AI, Search Algorithms, Knowledge Representation, Cloud Computing
  6. Digital Logic & Computer Organization: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design, Programming the Basic Computer
  7. TOC & Compiler: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Complexity Theory, Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  8. Discrete Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic
  9. Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS, Linux OS, Distributed Systems
  10. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Object Oriented Technology, HTML Basics, JavaScript-Basics, Java, XML
  11. Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control, Database Recovery, Data Warehousing & Mining, Enhanced Data Models, NoSQL
  12. Other Recurring CS Topics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, Multimedia
  13. Live Classes: ISRO Live classes
  14. Full Mock Test:
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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