Practice Question (Gate 1991)

Duration: 2 min

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Module outline

  1. About Course: BTSC About Course
  2. Basics of Computer Science: Basics of COA, Number System, Number Representation
  3. Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory
  4. Data Structures & Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms
  5. Database Management Systems(DBMS): Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Relational Algebra, SQL, Transaction Management, Concurrency Control, Database Recovery
  6. Networking and Internet: Introduction to CN, Data Communication, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Application Layer, Hardware Basics, Network Access Technologies, Network Security
  7. Cyber Security Basics: Cyber Threats and Malware Attacks, Role of Internet and Web Services, Electronic Data Interchange and E-Commerce, Cyber Safety and Security
  8. C Programming (Programming Fundamentals): C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  9. C++, OOPs & Java (Programming Fundamentals): Java, OOPS with C++
  10. Python (Programming Fundamentals): Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules
  11. Web Development Basics: Internet Fundamentals, Web Design & Development, Protocols & Services, Web Publishing & Hosting, Server Side & Security, Emerging Technologies, JavaScript-Basics, HTML Basics
  12. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing
  13. Software and Hardware Tools: MS Office Applications, Unix OS, Linux OS
  14. Emerging Trends. AI & Social Ethics: Artificial Intelligence, Emerging Tech Trends, Society, Law & Ethics
  15. Full Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This short GATE 1991 practice question asks students to trace a stack operation sequence and identify the correct popped-value order. The on-screen prompt reads “Choose the correct alternatives (more than one may be correct) and write the corresponding letters only,” followed by the operation list: PUSH(10), PUSH(20), POP, PUSH(10), PUSH(20), POP, POP, POP, PUSH(20), POP. Four options are shown: a) 20,10,20,10,20; b) 20,20,10,10,20; c) 10,20,20,10,20; d) 20,20,10,20,10. The instructor solves it by drawing a vertical stack container and updating its state after each push or pop, recording the values removed. The traced popped sequence is 20, 20, 10, 10, 20, which matches option (b), marked with a green checkmark. The lesson emphasizes LIFO behavior: the most recently pushed item is popped first, and visualizing stack contents step by step prevents mismatches with the answer choices.

Chapters

  1. 0:00 – 1:47 00:00-01:47

    The clip presents a GATE 1991 stack question with the on-screen instruction “Choose the correct alternatives (more than one may be correct)” and the operation sequence “PUSH(10), PUSH(20), POP, PUSH(10), PUSH(20), POP, POP, POP, PUSH(20), POP.” Options a–d list possible popped sequences. The instructor draws a vertical stack container, pushes 10 then 20, pops the top value 20, continues through the remaining operations, and writes the popped sequence “20 20 10 10” plus the final pop, matching option (b) “20,20,10,10,20,” which is checked in green.

The core concept is stack LIFO tracing. The method shown is to maintain a visible stack state, apply each operation in order, and record every POP result. The worked example starts with an empty stack: PUSH(10) gives [10]; PUSH(20) gives [10,20]; POP removes 20; PUSH(10) and PUSH(20) rebuild the top; subsequent POPs remove 20, then 10, then 10; finally PUSH(20) and POP remove 20. The resulting sequence is 20,20,10,10,20, so option (b) is correct. For exam revision, students should practice writing the stack after each step and comparing only POP outputs to the options.

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