Basic Block & CFG PQ - 2

Duration: 15 min

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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.

This lecture segment focuses on constructing a Control Flow Graph (CFG) from three-address code, a fundamental concept in compiler design. The instructor begins by presenting a problem that requires determining the number of nodes and edges in the resulting CFG. The core methodology involves identifying 'leaders' within the code, which serve as the starting points for basic blocks. A leader is defined as either the first instruction of the code, a target of a jump statement (goto or conditional), or an instruction immediately following a jump. Once leaders are identified, the code is partitioned into basic blocks (labeled B1 through B8 in this example), where each block contains a sequence of instructions with no internal branches. The instructor then maps these blocks to nodes in the graph and draws edges to represent control flow, specifically handling conditional jumps by creating 'True' and 'False' branches. The process concludes with counting the total nodes and edges to solve the problem.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces a problem involving three-address code and asks the viewer to determine the number of nodes (basic blocks) and edges in the resulting Control Flow Graph (CFG). The visible text on screen displays a 12-line sequence of instructions including assignments, conditional jumps (if), and unconditional jumps (goto). The instructor begins by identifying 'leaders' or basic block start points within the provided code snippet, writing this term on the screen to emphasize its importance in partitioning the code.

  2. 2:00 – 5:00 02:00-05:00

    The instructor analyzes the three-address code snippet to construct the CFG by identifying basic blocks. He underlines jump targets and labels, specifically pointing out lines 3, 5, 7, and 11 as jump destinations. He then lists the starting line numbers of these basic blocks (1, 6, 9, 10, 3, 4) to determine the nodes for the CFG. The visible text includes specific instructions like 'if x < y goto 6' and 'goto 9', which are critical for identifying the flow of control.

  3. 5:00 – 10:00 05:00-10:00

    The instructor is solving the problem by identifying 'leaders' in the code, which are the starting points of basic blocks (lines 1, 6, 9, 10, 3, 4, 8, 12). He then begins to group these leaders into basic blocks, labeling the first block B1 containing line 1 and starting the second block B2 with line 3. He lists leaders as 1, 6, 9, 10, 3, 4, 8, and 12. He then proceeds to group the instructions into basic blocks (B1 through B5) based on these leaders, filling in instruction numbers for Basic Blocks B1 to B8 and beginning to draw the graph structure by connecting these blocks.

  4. 10:00 – 14:36 10:00-14:36

    The instructor finalizes the construction of a Control Flow Graph (CFG) for the given three-address code snippet. He identifies leaders and basic blocks, then draws edges representing control flow transitions like 'True' and 'False' branches. The process involves mapping code lines to nodes (B1 through B8) and connecting them according to the logic of `if` statements and `goto` commands. Finally, he counts the total number of nodes (basic blocks) and edges in the completed graph to solve the problem.

The lecture demonstrates a systematic approach to converting intermediate code into a Control Flow Graph, a key step in compiler optimization. The process relies on the precise identification of 'leaders' to define basic blocks, which are then used as nodes in the graph. The instructor emphasizes that jump targets and instructions following jumps must be leaders, ensuring all possible execution paths are captured. By mapping these blocks to nodes and drawing edges for control flow, including conditional branches labeled 'True' and 'False', the instructor visualizes how code executes. This method allows for accurate counting of nodes and edges, which is essential for analyzing program complexity and optimizing code. The example provided serves as a practical application of these theoretical concepts, showing how abstract rules apply to concrete code snippets.

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