External Fragmentation

Duration: 5 min

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Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. Paper 1 | General Studies: State Wise GK
  3. Paper 1 | Information and Communication Technology: Role of Internet and Web Services, Security in Mobile and Wireless Computing
  4. Paper 1 | Current Affairs: GK- Current Affairs
  5. Paper 2 | Discrete Mathematical Structure: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Probability
  6. Paper 2 | Digital Computer Organization And Architecture: Number System, Number Representation, Sequential Circuits, Combinational Circuit, 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. Paper 2 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  8. Paper 2 | Programming Languages & Object-Oriented Programming Concepts: Java, OOPS with C++, Java Fundamentals, Array, String, IO & References
  9. Paper 2 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  10. Paper 2 | Data Structure And Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Minimum Spanning Trees, Advanced Algorithms
  11. Paper 2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS
  12. Paper 2 | 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
  13. Paper 2 | 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
  14. Paper 2 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Transaction Management, Concurrency Control, Database Recovery, Database Security & Authorization, Enhanced Data Models
  15. Paper 2 | Computer Network And Information Security: Introduction to CN, Data Communication, Application Layer, Hardware basics, Cyber Threats and Malware Attacks, Network Security, 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
  16. Paper 2 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  17. Paper 2 | Current Trends & Technologies: Emerging Tech Trends, Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Fuzzy Sets, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms, Artificial Intelligence, Data Warehousing & Mining, Electronic Data Interchange and E-Commerce, Terms & Abbreviations
  18. Paper 2 | Full Length Mock Tests:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video lecture provides a comprehensive explanation of external fragmentation within the context of operating system memory management. The instructor defines external fragmentation as a condition arising from contiguous allocation policies where the total available memory space is sufficient to satisfy a process request, but the space is not contiguous, making allocation impossible. This results in significant memory wastage. The lesson progresses from the theoretical definition displayed on the screen to a practical visual demonstration using a memory block diagram. The instructor draws a memory region with a central allocated section and free blocks on either side, labeling them to show the distribution of free space. He uses specific numerical examples to illustrate why a process cannot be loaded even when the aggregate free memory exceeds the process size, highlighting the critical limitation of contiguous allocation.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor begins by displaying the definition of external fragmentation on the screen, stating it is a function of contiguous allocation policy. The text explicitly notes that space requested by a process might be available in memory but cannot be allocated if it is not contiguous. To visualize this, he draws a long horizontal rectangle representing a memory block. He shades a central portion of this rectangle with diagonal lines to represent an allocated region. He then writes the number '5' above the free blocks on the left and right sides of the allocated region, indicating the size of the available free space in those specific segments. This setup establishes the scenario where free memory exists but is fragmented, preventing a single large allocation.

  2. 2:00 – 4:55 02:00-04:55

    The instructor continues the explanation by introducing specific process sizes to test against the memory diagram. He writes the number '7' and '12' below the diagram to represent the size of incoming processes. He explains that a process requiring 7 units of memory cannot be allocated because the available free blocks are only 5 units each, even though their sum is 10. He briefly displays a photograph of a large family with the caption 'on Family Are Expecting Their 17th Child' as a humorous interlude or analogy. He returns to the diagram, writing '9' as another example, reinforcing that the lack of a single contiguous block of sufficient size prevents allocation. He concludes that this inability to utilize available free space due to non-contiguity is the essence of external fragmentation, emphasizing the wastage involved.

The lecture effectively bridges the gap between the abstract definition of external fragmentation and its practical implications in memory management. By using a simple visual model of memory blocks and specific numerical examples, the instructor clarifies why total free memory is not the only factor in allocation decisions. The key takeaway is that contiguous allocation policies suffer from this wastage when free space is scattered, preventing the loading of processes that could theoretically fit in the total available memory. This distinction is crucial for understanding memory management strategies.

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