Linked File Allocation

Duration: 7 min

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Module outline

  1. About the Course: About the Course
  2. Section 1 | Language (Hindi): भाषा, लिपि, ध्वनि, वर्ण, अक्षर, स्वर, व्यंजन, मात्रा और संयुक्ताक्षर, वर्तनी, वर्ण-विन्यास, अनुस्वार, अनुनासिक, चंद्रबिंदु और ‘र’ के रूप, शब्द, पद और शब्द-भेद, संज्ञा और सर्वनाम, विशेषण और क्रिया, लिंग, वचन, पुरुष और कारक, काल, वाच्य, वाक्य और वाक्य-भेद, संधि, समास, विलोम शब्द, पर्यायवाची शब्द, सामान्य अशुद्धियाँ, अनेक शब्दों के लिए एक शब्द, मुहावरे और लोकोक्तियाँ, अपठित गद्यांश और अपठित पद्यांश, Multi-Topic Content (Cross-Concept Material), वर्णमाला
  3. Section 1 | Language (उर्दू भाषा — 22 प्रश्न (निश्चित)): Spelling & Diacritics, Grammar (اسم, فعل, صفت, ضمیر), Vocabulary, Idioms & Proverbs, Comprehension
  4. Section 1 | Language (বাংলা / बांग्ला भाषा — 22 प्रश्न (निश्चित)): Bangla Script and Sounds, Bangla Grammar and Usage, Bangla Word Formation and Vocabulary, Reading and Text Interpretation
  5. Section 1 | Language (English): Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Pronoun, Verb, Adverb, Preposition, Articles, Determiner, Conjunction, Modals, Active Passive Voice (Voice), Direct and Indirect Speech, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Construction, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Verbal Analogy (Word Based Analogy), Facts, Inference and Judgements
  6. Section 2 | Primary Maths & Reasoning: Ratio and Proportion (Ratios), Divisibility Rules, Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Percentage, Average, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Mensuration and Geometry, Age Problems, Arithmetic, Powers and Exponents (Surds and Indices), Algebra, Probability, Trigonometry, Syllogisms, Seating Arrangements, Blood Relations, Directions (Direction Test), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Venn Diagram, Data Arrangement, Inequality, Analogy, Ranking, Order and Sequence
  7. Section 2 | General Awareness (GK + Current Affairs): Polity, Physics, Biology, State Wise GK, Chemistry, History, Geography, Indian Economy, Environment, GK- Current Affairs, Static General Knowledge
  8. Section 3 | Computer System and Org. (CSO): Basics of COA, Floating Point Rep, Cache Memory Organization, Instr Formats & Modes, Programming the Basic Computer, Input Output Organisation, Register Transfer and Microoperations, Control Unit Design
  9. Section 3 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, SQL, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control
  10. Section 3 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Process Synchronization
  11. Section 3 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics
  12. Section 3 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Minimum Spanning Trees, Shortest Path Algos
  13. Section 3 | Theory Of Computation & Compiler Design: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization
  14. Section 3 | Emerging Trends (AI, Societal Ethics & MS Office): Artificial Intelligence, Emerging Tech Trends, Society, Law & Ethics, MS Office Applications
  15. Section 3 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Maintenance and Configuration Management, Software Testing
  16. Section 3 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  17. Section 3 | OOPS, C++, JAVA, HTML: OOPS with C++, Java, HTML Basics, CSS
  18. Section 3 | Java: Java Fundamentals, Array, String, IO & References
  19. Section 3 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  20. Section 3 | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  21. Section 3 | Multimedia: Multimedia
  22. BPSC Previous Year Papers:
  23. BPSC Full Mock Tests:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces Linked Allocation as a file system method that solves the problems associated with contiguous allocation. The instructor explains that with this method, each file is treated as a linked list of disk blocks, which can be scattered anywhere on the physical disk. A key feature is that the directory contains pointers to both the first and last blocks of the file. The video covers the advantages, such as the elimination of external fragmentation and the ability for files to grow dynamically without pre-allocating a fixed size. It also details significant disadvantages, including the overhead of storing pointers, the inability to perform efficient random access, and reliability concerns if a pointer is damaged.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor begins by presenting a slide titled "Linked Allocation" which states that this method solves all problems of contiguous allocation. He explains that with linked allocation, each file is a linked list of disk blocks, and these blocks may be scattered anywhere on the disk. A diagram of a disk cylinder is shown with blocks numbered 0 through 31. The instructor points to a directory entry for a file named "jeep", which has columns for "file", "start", and "end". He traces a path through the blocks (1 -> 6 -> 10 -> 14 -> 18 -> 22 -> 26) to demonstrate how the blocks are linked together. He emphasizes that the directory contains a pointer to the first and last blocks of the file, allowing the system to traverse the entire file. The slide text reads: "The directory contains a pointer to the first and last blocks of the file."

  2. 2:00 – 5:00 02:00-05:00

    The lecture transitions to the advantages of linked allocation. The instructor explains that to create a new file, one simply creates a new entry in the directory. Each directory entry has a pointer to the first disk block of the file. To read a file, the system simply reads blocks by following the pointers from block to block. A major advantage is that the size of a file need not be declared when the file is created; a file can continue to grow as long as free blocks are available. He highlights that there is no external fragmentation with linked allocation, and any free block on the free-space list can be used to satisfy a request. He draws abstract linked list nodes to visualize the structure, reinforcing that blocks are linked sequentially regardless of physical location. The slide text reads: "There is no external fragmentation with linked allocation, and any free block on the free-space list can be used to satisfy a request."

  3. 5:00 – 7:04 05:00-07:04

    The instructor discusses the disadvantages of linked allocation. He notes that to find the i-th block of a file, one must start at the beginning of that file and follow the pointers until reaching the i-th block. Each access to a pointer requires a disk read, which is slow. Another disadvantage is the space required for the pointers, so each file requires slightly more space than it would otherwise. Reliability is also a problem; if a pointer is lost or damaged, the file chain is broken. He suggests partial solutions like using doubly linked lists or storing the file name and relative block number in each block, but notes these schemes require even more overhead. He draws a simple linked list diagram to illustrate the pointer chain. The slide text reads: "Yet another problem is reliability. Recall that the files are linked together by pointers scattered all over the disk, and consider what would happen if a pointer were lost or damaged."

The video provides a comprehensive overview of Linked Allocation in file systems. It begins by defining the concept and illustrating it with a disk diagram and directory structure. The instructor then details the advantages, such as eliminating external fragmentation and allowing dynamic file growth. Finally, he addresses the disadvantages, including slow random access, pointer overhead, and reliability issues, while proposing potential solutions like doubly linked lists. This progression helps students understand the trade-offs involved in file system design.

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