Swapping & Page Replacement

Duration: 24 min

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Inside: a video lesson and guided study material.

Module outline

  1. Paper - 1 | Unit - 1 | Teaching Aptitude: Concept and Objectives of Teaching / शिक्षण की अवधारणा एवं उद्देश्य, Levels of Teaching / शिक्षण के स्तर, Learner's Characteristics / शिक्षार्थी की विशेषताएँ, Learning: Nature and Theories / अधिगम: प्रकृति एवं सिद्धांत, Cognition, Memory and Metacognition / संज्ञान, स्मृति एवं अधिसंज्ञान, Factors Affecting Teaching / शिक्षण को प्रभावित करने वाले कारक, Effective Teaching and the Teacher / प्रभावी शिक्षण एवं शिक्षक, Instructional Objectives and Lesson Planning / अनुदेशनात्मक उद्देश्य एवं पाठ नियोजन, Methods of Teaching / शिक्षण विधियाँ, Offline and Online Teaching Methods / ऑफ़लाइन एवं ऑनलाइन शिक्षण विधियाँ, Teaching Support System / शिक्षण सहायक प्रणाली, Evaluation Systems / मूल्यांकन प्रणाली
  2. Paper - 1 | Unit - 2 | Research Aptitude: Research: Meaning, Features and Scientific Method / अनुसंधान: अर्थ, लक्षण व वैज्ञानिक विधि, Research Paradigms and Approaches / अनुसंधान के प्रतिमान एवं उपागम, Types of Research / अनुसंधान के प्रकार, Variables and Measurement / चर एवं मापन, Methods of Research / अनुसंधान की विधियाँ, Steps of Research / अनुसंधान के चरण, Sampling / प्रतिचयन, Tools and Methods of Data Collection / आँकड़ा संग्रह के उपकरण एवं विधियाँ, Data Analysis and Statistics in Research / आँकड़ा विश्लेषण एवं शोध सांख्यिकी, Thesis and Article Writing / शोध-प्रबंध एवं लेख लेखन, Application of ICT in Research / अनुसंधान में ICT का अनुप्रयोग, Research Ethics / शोध नैतिकता
  3. Paper - 1 | Unit - 3 | Comprehension: Literal Comprehension, Vocabulary and Language in Context, Inferential Comprehension, Critical Comprehension, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions)
  4. Paper - 1 | Unit - 4 | Communication: Communication: Meaning, Nature and Process / संचार: अर्थ, प्रकृति एवं प्रक्रिया, Types and Levels of Communication / संचार के प्रकार एवं स्तर, Verbal and Non-verbal Communication / मौखिक एवं अमौखिक संचार, Semiotics and Meaning / संकेत विज्ञान एवं अर्थ, Models and Theories of Communication / संचार के मॉडल एवं सिद्धांत, Effective Communication / प्रभावी संचार, Barriers to Communication / संचार की बाधाएँ, Classroom Communication / कक्षा संचार, Mass Media: Types and Evolution / जनसंचार माध्यम: प्रकार एवं विकास, Mass Media and Society / जनसंचार एवं समाज, Digital and New Media / डिजिटल एवं नव माध्यम, General Awareness (Legacy Paper 1) / सामान्य जागरूकता (पुराना पेपर 1)
  5. Paper - 1 | Unit - 5 | Mathematical Reasoning and Aptitude: Number System and Simplification / संख्या पद्धति एवं सरलीकरण, Algebra and Ages / बीजगणित एवं आयु, Percentage / प्रतिशतता, Ratio, Proportion, Partnership and Mixtures / अनुपात, समानुपात, साझेदारी एवं मिश्रण, Averages / औसत, Profit, Loss and Discount / लाभ, हानि एवं बट्टा, Simple and Compound Interest / साधारण एवं चक्रवृद्धि ब्याज, Time and Work / समय एवं कार्य, Speed, Time and Distance / चाल, समय एवं दूरी, Mensuration and Geometry / क्षेत्रमिति एवं ज्यामिति, Series / श्रेणी, Coding-Decoding / कूटलेखन-कूटवाचन, Relationships, Directions and Ranking / संबंध, दिशा एवं क्रम, Arrangements, Puzzles, Clock and Calendar / व्यवस्था, पहेलियाँ, घड़ी एवं कैलेंडर, Mathematical Foundations, Analysis
  6. Paper - 1 | Unit - 6 | Logical Reasoning: Structure of Arguments / युक्ति की संरचना, Terms, Definitions and Uses of Language / पद, परिभाषा एवं भाषा के उपयोग, Categorical Propositions / निरुपाधिक प्रतिज्ञप्तियाँ, Categorical Syllogism / निरुपाधिक न्यायवाक्य, Venn Diagrams / वेन आरेख, Deduction, Induction and Analogy / निगमन, आगमन एवं सादृश्यता, Fallacies / तर्कदोष, Indian Logic: Pramanas / भारतीय तर्कशास्त्र: प्रमाण, Anumana and Vyapti / अनुमान एवं व्याप्ति, Hetvabhasa / हेत्वाभास, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Aristotle / अरस्तू, Western Schools of Philosophy / पाश्चात्य दर्शन की विचारधाराएँ, Kant / कांट, Sadhana Paada / साधनपाद, Vaiśeṣika / वैशेषिक
  7. Paper - 1 | Unit - 7 | Data Interpretation: Data and Graphical Representation / आँकड़े एवं आलेखीय निरूपण, Data Interpretation: Tables / आँकड़ा निर्वचन: तालिका
  8. Paper - 1 | Unit - 8 | Information and Communication Technology: Computer Fundamentals and Hardware, Memory, Storage and Data Representation, Computer Software, Office Applications, Multimedia and File Formats, Computer Networks, Internet and World Wide Web, Email and Online Communication, Cyber Security, Digital Ethics, IPR and Society, Cloud and Distributed Computing, Emerging Technologies, ICT in Education and Governance, Cyber Threats and Malware Attacks, Role of Internet and Web Services, Electronic Data Interchange and E-Commerce, Internet Fundamentals, Web Design & Development, Web Publishing & Hosting, Emerging Technologies, Terms & Abbreviations, Society, Law & Ethics, Keyboard Shortcuts, Website, Browser & Services, Protection of Geographical Indications / भौगोलिक संकेतों का संरक्षण
  9. Paper - 1 | Unit - 9 | People Development and Environment: Ecosystems and Biodiversity / पारितंत्र और जैव विविधता, Human and Environment Interaction / मानव और पर्यावरण की अंतःक्रिया, Development and Environment / विकास और पर्यावरण, Natural Resources – Forests, Water and Soil / प्राकृतिक संसाधन: वन, जल और मृदा, Energy Resources / ऊर्जा संसाधन, Air Pollution / वायु प्रदूषण, Water Pollution and Treatment / जल प्रदूषण और उपचार, Noise Pollution / ध्वनि प्रदूषण, Waste Management / अपशिष्ट प्रबंधन, Environmental Health and Toxicology / पर्यावरणीय स्वास्थ्य और विषविज्ञान, Climate Change and Global Environmental Issues / जलवायु परिवर्तन और वैश्विक पर्यावरणीय समस्याएँ, Natural Hazards and Disaster Management / प्राकृतिक प्रकोप और आपदा प्रबंधन, Indian Environmental Laws and Policies / भारतीय पर्यावरण कानून और नीतियाँ, International Environmental Agreements / अंतर्राष्ट्रीय पर्यावरण समझौते, Environment / पर्यावरण, Geography / भूगोल, Factory and Industry Systems / कारखाना और उद्योग व्यवस्थाएँ, Earth Materials, Surface Features and Processes, Communicable Diseases and Immunization / संक्रामक रोग और प्रतिरक्षण
  10. Paper - 1 | Unit - 10 | Higher Education System: Education in Ancient India / प्राचीन भारत में शिक्षा, Ancient Centres of Higher Learning / प्राचीन भारत के उच्च शिक्षा केंद्र, Colonial Education Policies and Commissions / औपनिवेशिक काल की शिक्षा नीतियाँ और आयोग, Colonial Colleges, Universities and Reformers / औपनिवेशिक कॉलेज, विश्वविद्यालय व सुधारक, Education Commissions and Policies after Independence / स्वतंत्र भारत में शिक्षा आयोग और नीतियाँ, National Education Policy 2020 / राष्ट्रीय शिक्षा नीति 2020, Types of Higher Education Institutions / उच्च शिक्षा संस्थानों के प्रकार, Learning Programmes and Academic Credits / अधिगम कार्यक्रम और अकादमिक क्रेडिट, Professional, Technical and Skill-Based Education / व्यावसायिक, तकनीकी और कौशल आधारित शिक्षा, Value Education and Environmental Education / मूल्य शिक्षा और पर्यावरण शिक्षा, Governance, Administration and Financing / शासन, प्रशासन और वित्तपोषण, Regulation, Accreditation and Ranking / उच्च शिक्षा का नियमन, प्रत्यायन और रैंकिंग, Indian Polity and Governance (Legacy Unit 10) / भारतीय राजव्यवस्था और शासन (पुराना यूनिट 10)
  11. Paper 2 | Unit 1 | Discrete Structures and Optimization: Propositional and Predicate Logic, Set Theory, Relations, Functions, Permutation, Combination and Probability / क्रमचय, संचय एवं प्रायिकता, Graph Theory, Group Theory, Digital Systems & Boolean Basics, Boolean Expression, Boolean Minimization, Optimization, Markov Chains
  12. Paper 2 | Unit 2 | Computer System Architecture: Logic Gates & Hardware, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep, Basics of COA, Register Transfer and Microoperations, Programming the Basic Computer, Instr Formats & Modes, Control Unit Design, Pipelining, Input Output Organisation, Cache Memory Organization, Multiprocessors
  13. Paper 2 | Unit 3 | Programming Languages and Computer Graphics: Language Design, C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, HTML Basics, XML, JavaScript-Basics, Java, Basics of Computer Graphics, 2-D Geometrical Transforms and Viewing, 3-D Object Representation, Geometric Transformations and Viewing, OOPS with C++, Java Fundamentals, Array, String, IO & References, OOPS with Java
  14. Paper 2 | Unit 4 | 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, Database Recovery, ORDBMS, Database Security & Authorization, Query Processing & Optimization, Enhanced Data Models, Data Warehousing & Mining, Big Data Systems, NoSQL
  15. Paper 2 | Unit 5 | System Software and Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management, Windows OS, Linux OS, Security, Distributed Systems, Virtual Machines
  16. Paper 2 | Unit 6 | 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 | Unit 7 | Data Structures and Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  18. Paper 2 | Unit 8 | Theory of Computation and Compilers: 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, 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
  19. Paper 2 | Unit 9 | Data Communication and 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, Cloud Computing, Mobile Computing
  20. Paper 2 | Unit 10 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Fuzzy Sets, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  21. Full Notes: Paper 1 Full Notes
  22. Paper 1 | Full Mock Tests:
  23. Paper 2 | Full Mock Tests:
  24. Paper 1 | Previous Year Papers:
  25. Paper 2 | Previous Year Papers:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces swapping and page replacement in operating systems. Swapping moves a process or its memory pages between RAM and secondary storage to free RAM when memory is under pressure, represented as a bidirectional relationship: RAM ↔ Swap Space. Page replacement occurs when a page fault happens and no free frame is available; the OS must select a page to remove, and the selected page is replaced by the required page. The instructor uses a hand-drawn diagram of memory frames containing pages 1, 2, 3, and 4 to illustrate a page fault requiring a new page (5). The lecture then covers specific page replacement algorithms. FIFO (First-In, First-Out) replaces the page that has been in memory for the longest time and maintains pages in arrival order. It is simple to implement but may suffer from Belady's Anomaly. A worked example uses the page reference string 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1 with 4 page frames. The instructor marks hits (H) and misses (M) above each reference number and fills a grid to track the state of memory frames over time. The Optimal (OPT) algorithm replaces the page that will not be used for the longest time in the future, producing the minimum possible number of page faults. It is used mainly as a benchmark and cannot be perfectly implemented in practice because future references are unknown. In the worked example, OPT yields a total of 4 page faults (PF=4). The Least Recently Used (LRU) algorithm replaces the page that has not been used for the longest time in the past and is based on past references. The lecture also introduces NRU (Not Recently Used), which uses Reference and Modified bits to classify pages into four classes for replacement, and the Clock/Second Chance algorithm, which improves upon FIFO by giving pages a second chance before replacement (R=0 -> Replace the page). The segment concludes with a comparative table of FIFO, Optimal, LRU, NRU, and Clock algorithms, highlighting their basis and whether they exhibit Belady's Anomaly.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The slide titled 'Swapping & Page Replacement' defines the core concepts. Under Swapping, bullets read: 'Swapping moves a process or its memory pages between RAM and secondary storage' and 'Used to free RAM when memory is under pressure,' followed by the relationship 'RAM ↔ Swap Space.' Under Page Replacement, bullets state: 'When a page fault occurs and no free frame is available, the OS must select a page to remove' and 'The selected page is replaced by the required page.' The instructor highlights key terms like RAM and secondary storage, circles 'RAM <-> Swap Space' in red ink to emphasize bidirectional movement, and underlines key terms in the page replacement section.

  2. 2:00 – 5:00 02:00-05:00

    The instructor introduces a hand-drawn diagram of memory frames containing pages 1, 2, 3, and 4 to illustrate a page fault requiring a new page (5), writing the number '5' with an arrow pointing to a frame. The lecture then introduces the FIFO (First-In, First-Out) page replacement algorithm, explaining that it replaces the page in memory for the longest time and maintains pages in arrival order. Key properties highlighted include 'Simple to implement' and 'May suffer from Belady's Anomaly.' A specific example is presented with a page reference string of 20 numbers and 4 page frames, asking the viewer to calculate the total number of page faults. A grid is provided below the string for tracking the state of memory frames over time.

  3. 5:00 – 10:00 05:00-10:00

    The instructor demonstrates the FIFO page replacement algorithm using the reference string 7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1 and 4 physical memory frames. Page hits (H) and misses (M) are annotated above each reference number as the algorithm progresses. The memory frame table is progressively filled to show the state of the FIFO queue after each step. At 455s, the table shows frames containing 7, 0, 1, and 2 after processing the first few references. At 545s, the table shows frames containing 3, 4, 2, and 1 after processing up to the reference '0.' The instructor underlines specific parts of the example text such as 'page reference string' and '4 page frames.'

  4. 10:00 – 15:00 10:00-15:00

    The video covers the FIFO and Optimal (OPT) page replacement algorithms. It begins by explaining that FIFO replaces the page in memory for the longest time and maintains pages in arrival order, noting it may suffer from Belady's Anomaly. The instructor then transitions to the Optimal (OPT) algorithm, which replaces the page that will not be used for the longest time in the future to produce the minimum possible number of page faults. The OPT algorithm is used mainly as a benchmark and cannot be perfectly implemented in practice because future references are unknown. The instructor begins an OPT worked example with 4 frames, using a grid to track page faults and memory frames step-by-step.

  5. 15:00 – 20:00 15:00-20:00

    The instructor walks through the Optimal (OPT) algorithm, identifying pages to replace based on future references and calculating a total of 4 page faults (PF=4) written at the bottom of the slide. The topic then shifts to the Least Recently Used (LRU) page replacement algorithm, which replaces the page that has not been used for the longest time in the past and is based on past references. The instructor begins processing the same reference string using LRU, marking hits (H) and misses (M) above the reference string to track faults. Key terms like 'future' for OPT and 'past' for LRU are highlighted to distinguish the algorithms.

  6. 20:00 – 24:19 20:00-24:19

    The segment introduces NRU (Not Recently Used), which uses Reference and Modified bits to classify pages into four classes for replacement, with on-screen text showing 'R (Reference Bit) = 1' and 'M (Modified Bit) = 0.' The Clock/Second Chance algorithm is introduced as an improved FIFO version, with a visual diagram of the circular/clock structure and the rule 'R=0 -> Replace the page.' The segment concludes with a comparative table of FIFO, Optimal, LRU, NRU, and Clock algorithms, highlighting their basis and whether they exhibit Belady's Anomaly. Important concepts like 'second chance' are underlined and circled.

The lecture progresses from foundational definitions to algorithmic implementations. It starts by defining swapping as the movement of processes or pages between RAM and secondary storage to alleviate memory pressure, and page replacement as the mechanism triggered when a page fault occurs with no free frames available. A hand-drawn diagram of memory frames (pages 1-4) with an incoming page (5) visually grounds the concept. The core of the lecture is a comparative analysis of five page replacement algorithms, each demonstrated with the same 20-number reference string and 4 frames to allow direct comparison. FIFO is presented first as the simplest approach, replacing the oldest page in arrival order, but it is noted to suffer from Belady's Anomaly. The worked example meticulously tracks hits and misses in a grid, showing the frame state evolving from [7,0,1,2] to [3,4,2,1]. OPT is introduced as the theoretical benchmark that minimizes faults by looking ahead into future references; it yields only 4 page faults in the example but is impractical because future references are unknown. LRU mirrors OPT's logic but looks backward at past usage, replacing the least recently used page. NRU and Clock/Second Chance are introduced as practical approximations; NRU uses R and M bits to classify pages, while Clock gives FIFO a 'second chance' by checking the reference bit before replacement. The final comparative table synthesizes these algorithms by their basis (past, future, bits) and susceptibility to Belady's Anomaly. The teaching method relies heavily on step-by-step grid tracking, H/M annotations above the reference string, and red-ink highlighting of key terms to guide student attention through each algorithm's decision logic.

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