12.11 Factorial of a Positive Number

Duration: 5 min

This video lesson is available to enrolled students.

Return to /learn/RSSB-SENIOR-COMPUTER-INSTRUCTOR/paper-2-python/control-flow-looping/loop-programs/asset-1211-factorial-of-a-positive-number after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About the Course: About the Course
  2. Paper-1 & 2 | Basic Numeracy: Ratio and Proportion (Ratios), Divisibility Rules, Mixture and Alligation, Permutation and Combination, Logarithm, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Percentage, Average, Mensuration and Geometry, Age Problems, Arithmetic, Statistics, Probability, Profit and Loss, Simple Interest and Compound Interest, Partnership, Speed Mathematics and Basic Mathematics, Algebra, Powers and Exponents (Surds and Indices), Time and Work, Pipe and Cistern, RSSB Specific Videos - Basic Numeracy
  3. Paper-1 & 2 | Data Interpretation: Data Interpretation
  4. Paper-1 & 2 | General Mental Ability: Mental Ability, RSSB Specific Videos - Mental Ability
  5. Paper-1 & 2 | Logical Reasoning and Analytical Ability: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Data Sufficiency, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Syllogisms, Seating Arrangements, Blood Relations, Directions (Direction Test), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Venn Diagram, Analogy, Ranking, Order and Sequence, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Data Arrangement, Logical Sequence Of Words, Crypt Arithmetic
  6. Paper-1 & 2 | Decision Making and Problem Solving: Selection Decision Table (Decision Making)
  7. Paper-1 | General Science: Physics, Biology, Chemistry, RSSB Specific Videos
  8. Paper-1 | General Awareness: State Wise GK, GK- Current Affairs
  9. Paper-2 | Fundamentals of Computer: Basics of COA, Number System, Floating Point Rep, Number Representation
  10. Paper - 2 | Digital Logic Systems: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits
  11. Paper-2 | Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Linux OS, Distributed Systems
  12. Paper-2 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Relational Calculus, File Organization & Indexing, Transaction Management, Concurrency Control
  13. Paper-2 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  14. Paper-2 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  15. Paper 2 | Oops, C++, Java: Language Design, OOPS with C++, Java, .Net Programming, Java Fundamentals
  16. Paper 2 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  17. Paper 2 | Emerging Trends and AI: Emerging Tech Trends, Artificial Intelligence
  18. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Advanced Algorithms
  19. Paper 2 | Data Communication and Network Security: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, 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, Ethical Hacking
  20. Paper-2 I Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  21. Paper-2 | Computer Organization and Architecture: Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations
  22. Paper-2 | Web Development: JavaScript-Basics, HTML Basics, CSS, XML
  23. Pedagogy: Child Development, Concept of Pedagogy, Psychology, Theories, Inclusive Education, Experiential Pedagogy, Curriculum Framework & Reforms, National Education Policy (NEP) 2020
  24. Live Sessions: RSSB Live Sessions
  25. RSSB Paper 1 - Full Mock Tests:
  26. RSSB Paper 2 - Full Mock Tests:
  27. SCI Previous Year Papers:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This video is a comprehensive educational lecture on calculating the factorial of a positive number using Python, presented by an instructor in front of a digital screen. The lecture begins with a definition of factorial, showing the mathematical formula n! = n x (n-1) x (n-2) x ... x 1, and provides a worked example for 5!. The main content is divided into three distinct methods: first, calculating the factorial using a for loop, where the code is written and the logic is explained step-by-step with a trace for n=5; second, calculating the factorial using a while loop, with the corresponding code and a similar trace; and third, calculating the factorial using recursion, where a recursive function is defined and its call stack is diagrammed for the input 5. The video concludes with a 'Thanks' message from the instructor.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title slide that reads 'Factorial of a Positive Number'. The instructor, standing in front of a digital screen, begins by explaining the mathematical concept of factorial. He writes the formula n! = n x (n-1) x (n-2) x ... x 1 on the screen and provides a concrete example, calculating 5! as 5 x 4 x 3 x 2 x 1, which equals 120. This section establishes the foundational knowledge required for the programming examples that follow.

  2. 2:00 – 5:00 02:00-05:00

    The instructor transitions to the first programming method, titled 'Factorial Using for Loop'. He displays a Python code snippet that takes a positive integer input, initializes a variable 'fact' to 1, and uses a for loop with the range function to multiply 'fact' by each number from 1 to n. He then demonstrates the logic by tracing the loop for n=5, writing out the calculations: i=1, fact=1*1=1; i=2, fact=1*2=2; i=3, fact=2*3=6; i=4, fact=6*4=24; i=5, fact=24*5=120. He then moves to the second method, 'Factorial Using while Loop', showing the corresponding code and tracing it for n=5, with calculations: n=5, fact=1*5=5, n=4; n=4, fact=5*4=20, n=3; n=3, fact=20*3=60, n=2; n=2, fact=60*2=120, n=1; n=1, fact=120*1=120, n=0. The loop terminates as n is no longer greater than 0.

  3. 5:00 – 5:26 05:00-05:26

    The final method demonstrated is 'Factorial Using Recursion (Conceptual)'. The instructor writes a Python function 'def factorial(n):' with a base case 'if n == 0 or n == 1: return 1' and a recursive case 'return n * factorial(n-1)'. He then explains the concept of recursion by drawing a call stack diagram on the screen, showing the function calls for 'factorial(5)' as f(5) = 5 * f(4), f(4) = 4 * f(3), f(3) = 3 * f(2), f(2) = 2 * f(1), and f(1) = 1. The values are then unwound to calculate the final result. The video ends with the instructor saying 'Thanks'.

The video provides a clear, structured, and progressive lesson on calculating factorials in Python. It begins with the essential mathematical definition, then systematically introduces three different programming paradigms: iteration with a for loop, iteration with a while loop, and recursion. Each method is presented with a complete code example, a step-by-step trace of the logic, and a visual diagram (for recursion) to illustrate the process. This approach effectively teaches the core concept of factorial and demonstrates how to implement it in code using different control structures, making it a valuable resource for learning fundamental programming techniques.

Loading lesson…