Practice Question (Gate 1995)

Duration: 4 min

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Module outline

  1. About Course: About the Course
  2. Paper-2 | Programming & Data Structures: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  3. Paper-2 | Databases / DBMS & SQL: 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
  4. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  5. Paper-2 | Computer Networks & Security: 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 Access Technologies, Network Security
  6. Paper-2 | Digital Logic: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep
  7. Paper-2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  8. 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
  9. Paper-2 | Computer Organization & Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  10. 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
  11. Paper-1 | General Awareness: Polity, Physics, Biology, Chemistry, Static General Knowledge, GK- Current Affairs, History, Geography, Indian Economy, Environment
  12. Paper-1 | Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Data Interpretation, Blood Relations, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Clock, Calendar, Cubes & Dices, Directions (Direction Test), Analogy, Seating Arrangements, Analytical Reasoning (Counting Figures Reasoning)
  13. Paper-1 | Quantitative Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Speed Time and Distance, Average, Age Problems, Percentage, Profit and Loss, Time and Work, Pipe and Cistern, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Mensuration and Geometry, Probability, Statistics, Arithmetic, Algebra
  14. Paper-1 | English: Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Construction, Cloze Test (Cloze Passage)
  15. Coal India Previous Year Paper:
  16. Engineering Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Linear Algebra, Calculus
  17. Coal India Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture solves a GATE 1995 multiple-choice question asking for the postfix expression of A+B*(C+D)/F+D*E. The instructor writes the infix expression on a whiteboard and converts it step by step, beginning with the innermost parentheses. The subexpression (C+D) is replaced by its postfix form CD+, underlining the operator to track conversion order. The multiplication B*(CD+) is then grouped as BCD+*, and division by F gives BCD+*F/. The remaining addition A + ... and the final D*E term are processed to produce the complete postfix string ABCD+*F/+DE*+. The final answer is underlined at the bottom of the board and matches option (b). The method emphasizes operator precedence, associativity, and incremental replacement of subexpressions with their postfix equivalents.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with the GATE 1995 question: 'The postfix expression for the infix expression A+B*(C+D)/F+D*E is:' with four options. The instructor writes the full infix expression on the whiteboard, then begins conversion by underlining the + inside (C+D) and rewriting it as CD+. The expression becomes A+B*CD+/F+D*E, showing the first precedence-based simplification.

  2. 2:00 – 3:38 02:00-03:38

    The instructor continues the conversion, grouping B*CD+ as BCD+*, then applying division by F to form BCD+*F/. The remaining A + ... and D*E parts are processed, yielding the final postfix string ABCD+*F/+DE*+, which is underlined at the bottom of the board. This matches option (b), ABCD+*F/DE*++.

The core teaching point is the systematic infix-to-postfix conversion rule: process parentheses first, then apply operator precedence and associativity, replacing each subexpression with its postfix equivalent. The worked example demonstrates that (C+D) becomes CD+, B*(CD+) becomes BCD+*, and the full expression resolves to ABCD+*F/+DE*+. The underlining technique helps students track which operators have been moved. This method is directly applicable to similar GATE questions involving nested parentheses and mixed precedence.

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