External Fragmentation

Duration: 5 min

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Inside: a video lesson and guided study material.

Module outline

  1. Section A | English: Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Preposition, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Articles, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Verbal Analogy (Word Based Analogy)
  2. Section A | Quant Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Arithmetic, Algebra, Powers and Exponents (Surds and Indices), Average, Age Problems, Percentage, Profit and Loss, Partnership, Time and Work, Simple Interest and Compound Interest, Mensuration and Geometry, Probability, Pipe and Cistern
  3. Section A | Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Calendar, Clock, Blood Relations, Directions (Direction Test), Seating Arrangements, Ranking, Order and Sequence, Puzzle Solving (Puzzles)
  4. Section B | C Programming: C Programming by Yash Sir, Coding Questions by Yash Sir
  5. Section B | Data Structures: Algorithm Analysis, Greedy Algorithms, Time Complexity Analysis, Sorting Algorithms, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs
  6. Section B | OOP (C++): Object Oriented Programming (OOPS), Programming in C++
  7. Section B | OS: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS
  8. Section B | Networking: 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
  9. Section B | AI & Big Data Basics: AI & ML by Arun Sir, Big Data Systems
  10. Section C | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Analog-Digital Conversion
  11. Section A, C | Comp. Fundamentals, COA: Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Multiprocessors, Programming the Basic Computer
  12. MOCK TEST:
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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