External Fragmentation

Duration: 5 min

This video lesson is available to enrolled students.

Return to /learn/UPPSC-POLYTECHNIC-LECTURER-2025-CS/paper-2-operating-systems/memory-management/contiguous-allocation/asset-external-fragmentation after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About Course: UPPSC Course Overview
  2. Interview Preparation & Guidance: Interview Preparation
  3. Paper 1 | General 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, वर्णमाला, समास, संधि, 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)
  4. Paper 2 | General Studies: State Wise GK, Polity, Geography, History, GK- Current Affairs
  5. Paper 1 | Programming Language: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, OOPS with C++
  6. Paper 1 | 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
  7. Paper 1 | Cyber Security: Society, Law & Ethics, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Electronic Data Interchange and E-Commerce, Physical Security and Cryptography Basics, Intrusion Detection Systems (IDS), Cyber Safety and Security, Ethical Hacking
  8. Paper 1 | 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
  9. Paper 1 | 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
  10. Paper 1 | Design and Analysis of Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  11. Paper 1 | Data Structures: Introduction to DS, Array, Linked List, Stack, Queue, Tree, Graphs, Hashing
  12. Paper 1 | Discrete Structures and Theory of Logic: Permutation and Combination, Set Theory, Relations, Functions, Propositional and Predicate Logic, Graph Theory, Group Theory
  13. Paper 1 | Software Project Management: Software Project Management
  14. Paper 2 | 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
  15. 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, Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Pushdown Automata & CFG, Complexity Theory
  16. Paper 2 | Artificial Intelligence & High Performance Computing: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Natural Language Processing, Emerging Tech Trends
  17. Paper 2 | Image Processing: Digital Image Fundamentals, Image Enhancement, Image Restoration, Color Image Processing, Image Compression
  18. 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
  19. Paper 2 | Computer Graphics: Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing
  20. Paper 2 | Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, HTML Basics, JavaScript-Basics, Java
  21. Paper 2 | Soft Computing: Fuzzy Sets, Artificial Neural Networks, Genetic Algorithms
  22. Paper 2 | Distributed System: Distributed Systems
  23. UPPSC Live Class Recordings: UPPSC Polytechnic Lecturer 2025 (CS)
  24. Previous Year Papers:
  25. 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.

Loading lesson…