SizeOf Operator

Duration: 8 min

This video lesson is available to enrolled students.

Return to /learn/UPPSC-COMPUTER-OPERATOR-GRADE-B/programming-languages/c-fundamentals/understanding-operators/asset-sizeof-operator after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. English Comprehension: Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Reading Comprehension, Vocabulary, Idioms and Phrases, Narrative Sequencing, Critical Reasoning
  2. Reasoning and Aptitude: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Analogy, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Logical Sequence Of Words, Seating Arrangements, Puzzle Solving (Puzzles), Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Data Sufficiency, Selection Decision Table (Decision Making), Calendar, Clock, Cubes & Dices, Data Arrangement, Venn Diagram, Analytical Reasoning (Counting Figures Reasoning), Number System, HCF LCM, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Simple Interest and Compound Interest, Speed Time and Distance, Mensuration and Geometry, Arithmetic, Mixture and Alligation, Age Problems, Data Interpretation, Alphabet and Word Tests, Numerical Reasoning, Number System, Averages, Mixtures and Alligation, Percentages, Series Completion, Analogy and Classification, Patterns in Two-Dimensional Figures, Coding and Decoding, Mathematical Operations, Direction Sense, Logical Deduction and Induction, Simplification and Approximation, Assembling and Grouping of Shapes, Transformation of Shapes, Three-Dimensional Patterns and Visualization, Cubes and Dice, Algebra, Traverse Surveying, Clocks and Calendars, Order, Ranking and Sequence, Constraint Puzzles, Syllogisms and Venn Diagrams, Ratio and Proportion, Mensuration, Permutations and Combinations, Project Monitoring, Resources and Safety, Profit, Loss and Discount, Sequences and Series, Powers, Surds and Logarithms, Subject-Verb Agreement, Sentence Completion, Geometry, Probability, Trigonometry, Measurement and Quantity Take-Off, Statistics, Data Sufficiency, Blood Relations, Speed, Time and Distance, Time and Work, Data Interpretation, Sequence and Series (Series), Algebra, Permutation and Combination, Combinatorics
  3. General Awareness: Physics, Chemistry, Biology, Geography, History, Polity, Indian Economy
  4. Computer Fundamentals: Basics of COA, Number System, Number Representation, Semiconductor Memories and Programmable Logic, Timing, Hazards and Testing, Processor Organization and Instructions, Number Systems and Codes, Combinational Logic Design, Combinational Logic Circuits, Number Systems and Codes
  5. Operating System: Introduction to OS, Unix OS, Linux OS
  6. C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  7. OOPS with C++ & Java: OOPS with C++, Java
  8. Database Management System: Basics of DBMS, SQL
  9. MS Office: MS Office Applications
  10. Internet & Web Technologies: Website, Browser & Services, Internet Fundamentals, Web Design & Development, Protocols & Services
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture introduces the sizeof() operator in C, defining it as a compile-time mechanism that determines the size of data types or variables in bytes. A central teaching point is that expressions within sizeof() are not executed, meaning side effects like assignments do not occur. The instructor uses specific code examples to demonstrate that while sizeof() returns the size of an integer (e.g., 2 bytes on a 16-bit machine), variables modified inside the operator remain unchanged. The syntax allows sizeof to be applied to variables, types, values, or expressions.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video begins by defining the sizeof() operator as a tool to find the size in bytes of a datatype, variable, or expression. The slide explicitly states it is the only operator evaluated at compile time. A key rule highlighted with red circles and underlining is that expressions inside sizeof are not executed. The instructor presents the syntax sizeof (variable | type | value | expression) and uses a code example where int x = sizeof(a = 10); is shown. The output explanation clarifies that while x stores the size of an integer (2 bytes), the variable a remains 5 because the assignment inside sizeof is ignored.

  2. 2:00 – 5:00 02:00-05:00

    The final segment revisits the core concept that sizeof() is evaluated at compile time and expressions are not executed. The instructor uses printf statements to show the output of a variable that was never modified inside sizeof(). The slide displays int x = sizeof(a > 10); to show that even relational expressions are not evaluated for their truth value but only for the size of the result type. The output remains consistent: a is 5, and x holds the integer size (2 bytes). This reinforces that sizeof() operates on types rather than runtime values.

  3. 5:00 – 8:29 05:00-08:29

    The lecture continues to reinforce the non-execution rule of expressions within sizeof(). The instructor emphasizes that side effects, such as assignments or increments, do not happen inside the operator. A code snippet demonstrates int a = 5; followed by sizeof(a = 10), where the output confirms a is still 5. The slide notes that sizeof returns the size of an integer, which varies by architecture (e.g., 2 bytes on a 16-bit machine). Handwritten annotations show arithmetic like 10 + 3 to illustrate that sizeof evaluates the type size, not the expression result.

The lecture establishes that sizeof() is a compile-time operator unique for not executing its operand expressions. This prevents side effects, ensuring variables retain their original values even if modified inside sizeof(). The operator returns the byte size of a type, which depends on the machine architecture (e.g., 2 bytes for int on 16-bit systems). Examples consistently show that assignments like a = 10 inside sizeof(a = 10) are ignored, and the variable remains unchanged. The syntax supports variables, types, values, or expressions, but only the type size is returned.

Loading lesson…