Contiguous File Allocation

Duration: 9 min

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Inside: a video lesson and guided study material.

Module outline

  1. General Intelligence & Reasoning: Analogy, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Logical Sequence Of Words, Syllogisms, Venn Diagram, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Data Sufficiency, Puzzle Solving (Puzzles), Data Arrangement, Cubes & Dices, Calendar, Clock, Arithmetic, Number System, HCF LCM, Verbal Analogy (Word Based Analogy), Visual Recognition and Figure Completion, Paper Folding and Cutting, Transformation of Shapes, Clocks and Calendars, Direction Sense, Cubes and Dice, Patterns in Two-Dimensional Figures, Seating Arrangements, Analogy and Classification, Logical Deduction and Induction, Alphabet and Word Tests, Mathematical Operations, Series Completion, Simplification and Approximation, Coding and Decoding, Numerical Reasoning, Assembling and Grouping of Shapes, Three-Dimensional Patterns and Visualization, Vocabulary, Number System, Averages, Mixtures and Alligation, Simple and Compound Interest, Percentages, Algebra, Speed, Time and Distance, Seating and Arrangement Puzzles, Traverse Surveying, Order, Ranking and Sequence, Constraint Puzzles, Syllogisms and Venn Diagrams, Reading Comprehension, Critical Reasoning, Permutations and Combinations, Narrative Sequencing, Project Monitoring, Resources and Safety, Profit, Loss and Discount, Ratio and Proportion, Time and Work, Mensuration, Data Interpretation, Powers, Surds and Logarithms, Sequences and Series, Articles and Determiners, Sentence Completion, Data Sufficiency, Blood Relations, Simple Interest and Compound Interest, Mixture and Alligation, Sequence and Series (Series), Speed Time and Distance, Algebra, Profit and Loss, Powers and Exponents (Surds and Indices), Permutation and Combination
  2. General Awareness: Physics, Chemistry, Biology, History, Geography, Polity, Indian Economy, Environment, Static General Knowledge, GK- Current Affairs, Artificial Intelligence, MS Office Applications, Terms & Abbreviations, Keyboard Shortcuts, Evolution of Indian Banking (Banking & Financial Awareness), Emerging Tech Trends
  3. Engineering Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Linear Algebra, Calculus, Probability, Statistics, Signal Space and Optimum Detection, Probability, Statistics
  4. Digital Logic: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep, Number Systems and Codes, Registers and Counters, Boolean Algebra and Logic Gates, Microprocessors and Microcontrollers, Logic Families and CMOS Logic, Microprocessors, Logic Gates and Boolean Algebra, Minimization of Boolean Functions, Timing, Hazards and Testing, Logic Families, Combinational Logic Design, Arithmetic Circuits, Waveform Generators and Timer Circuits, Semiconductor Memories and Programmable Logic Devices, Combinational Logic Circuits, Latches and Flip-Flops, Finite State Machines, Sequential Circuits and State Machines, Minimization of Boolean Functions, Arithmetic Circuits, Latches and Flip-Flops, Number Systems and Codes, Registers and Counters
  5. Computer Organisation & Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer, Register Transfer and Microoperations, Semiconductor Memories and Programmable Logic, Processor Organization and Instructions, Memory Hierarchy and Input/Output, Registers and Counters
  6. Programming & Data Structures: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, HTML Basics, OOPS with C++, Java, Object Oriented Technology
  7. Databases: 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, Database Security & Authorization
  8. Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  9. Theory of Computation: 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
  10. 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
  11. Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Security, Windows OS, Distributed Systems, Unix OS, Linux OS
  12. Computer Networks: Introduction to CN, 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, Data Communication, Website, Browser & Services, Web Design & Development, Network Security, Cyber Threats and Malware Attacks, Cyber Safety and Security
  13. Full Length Mock Tests:
  14. Sectional Tests:
  15. Paper 2 - Full-length Mock Tests:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video lecture focuses on the concept of Contiguous Allocation within file systems. The instructor begins by defining the core requirement: each file must occupy a set of contiguous blocks on the disk. He explains that disk addresses create a linear ordering, which simplifies access patterns. Using a visual directory table and a disk block diagram, he demonstrates how files are mapped to specific starting blocks and lengths. The lecture then transitions to a critical evaluation of the method, discussing its advantages in terms of access speed and its significant disadvantages related to external fragmentation and file modification constraints. He uses hand gestures to point out specific elements on the slide.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the topic "Contiguous Allocation" with a slide stating that each file must occupy a set of contiguous blocks on the disk. He explains that disk addresses define a linear ordering, meaning accessing block b+1 after block b normally requires no head movement. He displays a directory table with columns for "file", "start", and "length". He points to the entry for "count", which starts at block 0 with a length of 2, indicating it occupies blocks 0 and 1. He writes "DBA" (Disk Block Address) next to block 0 on the disk diagram to emphasize the starting point. The slide text explicitly mentions "assuming that only one job is accessing the disk". The disk diagram shows blocks numbered sequentially from 0 to 31 in a cylindrical shape. He uses his hand to point at the specific blocks on the diagram. He also points to the "count" label in the directory.

  2. 2:00 – 5:00 02:00-05:00

    The instructor elaborates on the directory table entries to show how different files are allocated. He points to "tr" starting at block 14 with length 3, "mail" starting at 19 with length 6, "list" starting at 28 with length 4, and "f" starting at 6 with length 2. He draws a physical disk platter diagram to visualize how these blocks are arranged on the actual hardware, drawing concentric circles for tracks and lines for sectors. He explains that this linear ordering allows for efficient access patterns. He highlights that because the blocks are contiguous, the disk head does not need to move significantly between blocks of the same file, which improves performance for sequential access. He gestures towards the directory table to reinforce the mapping logic. The "mail" file occupies blocks 19 through 24. He draws lines on the disk diagram to represent the tracks. He also points to the "mail" entry in the directory.

  3. 5:00 – 9:00 05:00-09:00

    The lecture shifts to the pros and cons of this allocation method. A slide lists "Advantage" as easy access supporting both sequential and direct access. The "Disadvantage" section mentions suffering from external fragmentation. The instructor explains that deleting a file leaves a hole, and if a new file is too large for that hole, it cannot be placed there. He discusses the difficulty of file modification; if a file grows larger than its allocated contiguous space, it cannot simply expand. He writes "1KB" and "700B" on the disk diagram, likely illustrating block sizes or file size constraints relative to available space. He concludes that while efficient for access, the fragmentation issue is a significant drawback. The slide text explicitly lists "Suffer from the problem of external fragmentation" and "Another problem with contiguous allocation file modification". A copyright banner "THIS IS COPYRIGHTED CONTENT OF KNOWLEDGEGATE EDUVENTURES" is visible at the bottom. He points to the disadvantage bullet points on the slide. He also writes "1KB" and "700B" on the board.

The video provides a comprehensive overview of contiguous allocation, starting with the fundamental definition of storing files in contiguous blocks. It progresses to practical examples using a directory table and disk diagrams to show how files like "count", "tr", and "mail" are mapped to physical blocks. The instructor then transitions to a critical analysis of the method, highlighting the primary advantage of efficient sequential and direct access due to linear ordering. However, he emphasizes the major disadvantages, specifically external fragmentation and the inability to easily modify file sizes, which limits the flexibility of this allocation method in dynamic file systems. He uses visual aids to clarify complex concepts.

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