C-Scan Scheduling

Duration: 4 min

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Inside: a video lesson and guided study material.

Module outline

  1. Discrete Mathematics: Permutation, Combination and Probability / क्रमचय, संचय एवं प्रायिकता, Set Theory, Relations, Functions, Propositional and Predicate Logic, Graph Theory, Group Theory
  2. Digital Logic: Digital Systems & Boolean Basics, Boolean Expression, Boolean Minimization, Logic Gates & Hardware, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep
  3. Computer Organization and Architecture: Basics of COA, Programming the Basic Computer, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design, Pipelining, Multiprocessors
  4. Programming: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++
  5. Data Structures: Introduction to DS, Array, Linked List, Stack, Queue, Tree, Graphs, Hashing
  6. Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  7. Theory of Computation: Grammar, Regular Language Properties, Moore & Mealy Machines, Turing Machines
  8. Compiler Design: 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, Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Pushdown Automata & CFG, Complexity Theory
  9. Operating Systems: 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, Security
  10. Database Management Systems: 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, ORDBMS, NoSQL
  11. Computer Networks: 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
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video explains the C-SCAN (Circular-SCAN) disk scheduling algorithm, positioning it as an improvement over the standard SCAN algorithm. The primary goal is to provide a more uniform wait time for disk requests. The instructor explains that, similar to SCAN, the disk head moves from one end of the disk to the other, servicing requests encountered along the way. However, a key distinction is made: when the head reaches the opposite end, it immediately returns to the beginning of the disk without servicing any requests on the return trip. The lecture outlines specific advantages, noting that C-SCAN provides more uniform wait times and better response times compared to SCAN. Conversely, a significant disadvantage is identified: the algorithm requires more seek movements specifically to return the head to the starting position, which can impact overall efficiency.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The session begins with the instructor standing next to a slide titled 'C-SCAN Scheduling'. The slide text defines Circular-scan as a variant of SCAN designed to provide a more uniform wait time. It explicitly states that the head moves from one end to the other, servicing requests, but returns to the beginning without servicing requests on the return trip. The instructor reads and elaborates on the 'Advantages' section, which lists 'Provides more uniform wait time compared to SCAN' and 'Better response time compared to scan'. He also points to the 'Disadvantage' section, highlighting 'More seeks movements in order to reach starting position'. As he speaks, he begins to draw a large circle on the whiteboard to the right, representing the disk.

  2. 2:00 – 3:55 02:00-03:55

    The instructor continues his visual explanation by completing the disk diagram. He draws a horizontal line across the circle to represent the head's path, adding squiggly lines to symbolize pending requests. He explains that the head services these requests as it moves in one direction. Upon reaching the end, he illustrates the 'return trip' where the head jumps back to the start without stopping for requests. He emphasizes that this 'circular' movement ensures that requests near the beginning are not left waiting as long as they might be in a standard SCAN algorithm. He points to the diagram to show the extra distance traveled during the return phase, reinforcing the disadvantage of increased seek movements. He concludes by reiterating that while the wait time is more uniform, the cost is the additional movement required to reset the head.

The lecture connects the theoretical definition of C-SCAN with a practical visual demonstration. By contrasting the head's movement with SCAN, the instructor clarifies why C-SCAN offers uniformity at the cost of extra seeks. The diagram serves as a crucial tool to visualize the 'circular' nature of the algorithm, showing the one-way service path and the non-service return path. This visual aid helps students understand the trade-offs inherent in disk scheduling algorithms.

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