You are an expert CBSE XII CS Computer Science teacher, examiner, and study material creator.

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SCOPE — READ BEFORE GENERATING ANYTHING
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Today's lecture covers ONE topic only: "Text file reading writing searching and counting"
Lecture number 27 of 91 | Duration: 35 minutes | Board: CBSE
Chapter: Computational Thinking and Programming – 2

HARD RULE: Every piece of content you generate — notes, examples, questions, tips —
must be directly relevant to "Text file reading writing searching and counting" only.
DO NOT pull content, examples, or questions from any other topic or chapter.

LECTURE MODE: THEORY / CONCEPT TEACHING
- Teach the concept first: definitions, intuition, examples, syntax/steps, and misconceptions.
- Use the given exam-frequency analysis internally to decide emphasis and short concept checks; keep the lecture concept-teaching focused.
- Keep content tightly scoped to today's concept list.

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SECTION 1: LECTURE INFORMATION
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Class: XII CS | Subject: Computer Science | Board: CBSE
Topic: Text file reading writing searching and counting Theory part 2
Subtopics to cover today:
- Text file reading writing searching and counting

Student level: Class XII, CBSE Board, average to above-average students preparing for board exams

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SECTION 2: TEACHER'S REFERENCE NOTES
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Text file reading writing searching and counting Theory part 2

Concept ID: U1_TEXT_FILE_OPERATIONS.
Primary Sub-subtopic: Text file reading writing searching and counting.
Question-bank grouping: File Handling.

Use this lecture for theory, examples, misconceptions, and short concept checks mapped to this concept ID.

Teaching ideas: Teach the concept first, then use a small number of concept-ID matched concept checks.

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SECTION 3: EXAM FREQUENCY DATA (Year-wise)
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Teaching priority: HIGH
High-yield concepts: Binary file operations with pickle, CSV file read write and search, Text file reading writing searching and counting, File basics paths modes seek and tell, Text file reading writing searching and counting, Text file reading writing searching and counting

| Year | Questions | Marks |
|------|-----------|-------|
| 2023 | 1 | 5 |
| 2024 | 9 | 28 |
| 2025 | 5 | 13 |
| 2026 | 2 | 6 |
| **Total** | **17** | **52** |

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SECTION 4: EXAM ANALYSIS INPUT — DO NOT PRINT THESE IN THEORY NOTES
(Scope: "Text file reading writing searching and counting" only — 17 questions from board papers)
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THEORY LECTURE RULE: use these PYQs only as private analysis data — this lecture is PURELY THEORY.
- Cover every concept and trap revealed by these PYQs in the study notes
- Do NOT print, quote, reproduce, paraphrase, or label any actual PYQ in the final HTML
- Self-generate your own tricky/important questions and examples about the concept itself only —
  do not call them "PYQ-pattern", "PYQ-style", "board-style", or reference PYQs/previous years at all
- In theory lectures, generated questions must be MCQ or Short Answer only
- Never use the word "PYQ" or phrases like "previous year question" anywhere in the visible HTML


--- 2023 Board Exam (1 question | 5 marks) ---

Q1. [Programming] [5M] [Hard] Section-D
(a) Write one difference between CSV and text files.
Write a program in Python that defines and calls the following user defined functions :
(i) COURIER_ADD(): It takes the values from the user and adds the details to a csv file 'courier.csv'. Each record consists of a list with field elements as cid, s_name, Source, destination to store Courier ID, Sender name, Source and destination address respectively.
(ii) COURIER_SEARCH() : Takes the destination as the input and displays all the courier records going to that destination.

(ii) Search_Book(): Takes publisher name as input and counts and displays number of books published by them.

--- 2024 Board Exam (9 questions | 28 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
Which of the following file opening mode is used to open a file in append and read mode ?
(A) r+
(B) w+
(C) a+
(D) x+

Q2. [Programming] [3M] [Medium] Section-C
(a) Write the user defined function count_words() in Python to count the number of words in a text file "Story.txt".

Q3. [Programming] [3M] [Medium] Section-C
(b) Write the user defined function display() in Python to read the content of a text file "Story.txt" and display those words which are less than 4 characters.

Q4. [Programming] [3M] [Medium] Section-C
(a) Write a method/function COUNTWORDS() in Python to read contents from a text file DECODE.TXT, to count and return the occurrence of those words, which are having 5 or more characters.

Q5. [Programming] [3M] [Medium] Section-C
(b) Write a method/function COUNTLINES() in Python to read lines from a text file CONTENT.TXT, and display those lines, which have @ anywhere in the line.
For example :
If the content of the file is :
Had an amazing time at the concert last night with
@MusicLoversCrew.
Excited to announce the launch of our new website!
G20 @ India
The method/function should display
Had an amazing time at the concert last night with
@MusicLoversCrew
G20 @ India

Q6. [Short Answer] [3M] [Medium] Section-C
A) Write a Python function that displays all the words containing @cmail from a text file "Emails.txt".

Q7. [Short Answer] [3M] [Medium] Section-C
B) Write a Python function that finds and displays all the words longer than 5 characters from a text file "Words.txt".

Q8. [Programming] [4M] [Medium] Section-E
Write a program in Python to read the content of a text file Story.txt and count and display the number of lines that start with the letter 'A'.

Q9. [Programming] [5M] [Hard] Section-E
(b) (i) Give one difference between write() and writeline() function in text file.

(ii) A Binary file, "Items.dat" has the following structure :
[Icode, Description, Price]
Where
Icode – Item code
Description – Detail of item
Price – Price of item
Write a function Add_data(), that takes Icode, Description and Price from the user and writes the information in the binary file "Items.dat".

--- 2025 Board Exam (5 questions | 13 marks) ---

Q1. [MCQ] [1M] [Easy] Section-A
A text file 'song.txt' contains the following contents in it :
Life goes on as it never ends
What will be the output of the following code snippet ?
f1=open("song.txt","r")
s1=f1.read(5)
s2=f1.readline(4)
s3=f1.read(3)
print(s1,s3,sep="#")
(A) goes# on
(B) Life #goes# on
(C) Life # on
(D) Error

Q2. [Programming] [3M] [Medium] Section-C
Write a user defined function in Python named COUNT() which counts and displays the number of lines which do not start with the vowels 'A' or 'E' in the file, "Paragraph.txt".

Q3. [Programming] [3M] [Medium] Section-C
(b) Write a function in Python to display the line which has the maximum number of vowels from a text file, "Novel.txt"

Q4. [Programming] [3M] [Medium] Section-C
A. Write a Python function that displays the number of times the word "Python" appears in a text file named "Prog.txt".

Q5. [Programming] [3M] [Medium] Section-C
B. Write and call a Python function to read lines from a text file STORIES.TXT and display those lines which doesn't start with a vowel (A, E, I, O, U) irrespective of their case.

--- 2026 Board Exam (2 questions | 6 marks) ---

Q1. [Short Answer] [3M] [Medium] Section-C
(a) Write a Python function that counts and returns the number of digits appearing in the text file "Space.txt". For example, if the file contains :
Space exploration has unlocked incredible
advancements in technology and science. Since the
first moon landing in 1969, space agencies have sent
probes to Mars, Jupiter and beyond. The ISS,
orbiting Earth at about 400 km, serves as a hub for
research. With missions planned for 2030, humanity's
cosmic journey continues!
Then the function should return 11.

Q2. [Short Answer] [3M] [Medium] Section-C
(b) Write a Python function that displays the words in which the lowercase letter 'e' appears at least twice in the text file 'Space.txt'. For example, if the file contains :
Space exploration has unlocked incredible
advancements in technology and science. Since the
first moon landing in 1969, space agencies have sent
probes to Mars, Jupiter and beyond. The ISS,
orbiting Earth at about 400 km, serves as a hub for
research. With missions planned for 2030, humanity's
cosmic journey continues!
Then the function should display :
incredible advancements science. agencies serves research.

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QUESTION PATTERN BANK (What the board actually asks for THIS topic)
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Scope: ONLY questions for today's lecture topic are listed below.
DO NOT import questions from other topics or chapters.
These are concept-pattern summaries (what TYPE the board asks), not copies of the
actual questions — never reproduce full question text here.

### Concept: Binary file operations with pickle
  Pattern: Programming=1 | Marks: 5M=1 | Total: 1 questions
  [Programming] [5M] [Hard]
    → Core concept of Binary file operations with pickle

### Concept: CSV file read write and search, Text file reading writing searching and counting
  Pattern: Programming=1 | Marks: 5M=1 | Total: 1 questions
  [Programming] [5M] [Hard]
    → Core concept of CSV file read write and search, Text file reading writing searching and counting

### Concept: File basics paths modes seek and tell, Text file reading writing searching and counting
  Pattern: MCQ=1 | Marks: 1M=1 | Total: 1 questions
  [MCQ] [1M] [Easy]
    → Core concept of File basics paths modes seek and tell, Text file reading writing searching and counting

### Concept: Text file reading writing searching and counting
  Pattern: MCQ=1, Programming=9, Short Answer=4 | Marks: 1M=1, 3M=12, 4M=1 | Total: 14 questions
  [Programming] [3M] [Medium] × 8
    → Core concept of Text file reading writing searching and counting
  [Short Answer] [3M] [Medium] × 4
    → Core concept of Text file reading writing searching and counting
  [Programming] [4M] [Medium]
    → Core concept of Text file reading writing searching and counting
  [MCQ] [1M] [Easy]
    → Output/result interpretation for the current concept


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IMPORTANCE ANALYSIS (allocate teaching time by this ranking)
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| Rank | Concept | Score | Times Tested | Total Marks | Recent Years | Priority |
|------|---------|-------|-------------|-------------|--------------|----------|
| 1 | Text file reading writing searching and counting | 108 | 14 | 41M | 2026, 2025, 2024 | CRITICAL |
| 2 | CSV file read write and search, Text file reading writing searching and counting | 13 | 1 | 5M | 2023 | HIGH |
| 3 | Binary file operations with pickle | 13 | 1 | 5M | 2024 | HIGH |
| 4 | File basics paths modes seek and tell, Text file reading writing searching and counting | 5 | 1 | 1M | 2024 | MEDIUM |

CRITICAL concepts → full sub-section + comparison table + 2 worked examples
HIGH concepts     → 1 sub-section + 1 worked example
MEDIUM concepts   → definition + 1 quick example only

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EXAMINER FINGERPRINT — TRAPS TO COVER INTERNALLY
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Use the exam-frequency input only for internal analysis. Do not print, quote, reproduce, paraphrase, or label any actual board question in the final HTML.

For this lecture, the generated teaching material must strongly cover these traps:

No static trap list exists yet for "Text file reading writing searching and counting". Self-generate 4–7 traps from:
- actual question patterns for Binary file operations with pickle, CSV file read write and search, Text file reading writing searching and counting, File basics paths modes seek and tell, Text file reading writing searching and counting, Text file reading writing searching and counting
- common wrong assumptions students make about this concept
- output-tracing traps
- syntax-vs-runtime traps
- comparison traps
- order/sequence traps

Important: this list should be treated as dynamic — for lectures with no static trap list, generate traps yourself from the categories above rather than leaving this section thin.
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YOUR TASK — Generate a complete classroom-ready teaching package
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Output format: FULL HTML (print-ready, A4, same format as CBSE study material).
Use the CSS classes below. NO plain Markdown — use HTML elements only.

HTML STRUCTURE TO GENERATE:

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<!-- TOC SIDEBAR -->
<nav class="toc-sidebar" aria-label="Table of Contents">
  <h4>&#128214; Contents</h4>
  <!-- TOC links auto-built by JS above -->
</nav>

<!-- MAIN CONTENT -->
<div class="main-content">

Generate these sections in order (all inside the main-content div):

<h1 id="top">Text file reading writing searching and counting Theory part 2 — Lecture 27</h1>
<p style="text-align:center;color:#555;font-size:8.5pt;">CBSE | XII CS | Computational Thinking and Programming – 2 | 35 min</p>

<h2 id="s1">1. Learning Objectives</h2>
[3–5 objectives derived from the exam-importance analysis above (never naming PYQs) — use &lt;ul&gt;&lt;li&gt;]

<h2 id="s2">2. 35-Minute Lecture Flow</h2>
[HTML table: Time | Activity | Teacher Action — include a concept-based recap/check slot — no PYQ discussion, no PYQ wording anywhere]

<h2 id="s3">3. Concept Notes</h2>
[For EVERY sub-concept surfaced by the exam-frequency analysis, never naming or displaying actual board questions:
  - .def-box for definition with "In exam language: ..." line
  - .key-box with syntax/rules as &lt;ul&gt;&lt;li&gt;
  - .example-box for worked examples
  - &lt;pre&gt;&lt;code&gt; for code with .kw/.bi/.st/.cm/.nm token spans
  - .recall-box for output with exact expected output
  - after each important concept, embed 1–2 self-generated MCQ or Short Answer checks about THIS concept only
  - every Section 3 check question must hide its answer inside:
    &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer/explanation&lt;/details&gt;
  - do not label any question as PYQ, previous year, board-style, PYQ-pattern, or PYQ-style
  - do not use .pyq-box or .pyq-meta here (in Combined mode .pyq-box is reserved for Section 7)
]

<h2 id="s4">4. Examiner Tricks &amp; Common Mistakes</h2>
[Create one .warn-box for each trap from the EXAMINER FINGERPRINT section.
Each .warn-box must be specific and must include:
  - the mistake students commonly make
  - the correct rule
  - a tiny example or wrong-vs-right explanation
Do not mention actual board questions, years, previous papers, PYQ, or source metadata.]

<h2 id="s5">5. Board Work Plan</h2>
[Numbered list: exactly what to write on the blackboard, in order]

<h2 id="s6">6. Classroom Practice Questions</h2>
[Self-generated from the examiner-trap patterns analysed above — never call these PYQ-pattern/PYQ-style/board-style. CRITICAL: every answer MUST be inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; — never expose the answer directly.

3×1M MCQ + 5×1-2M Short Answer only.
Theory lecture restriction:
- Do NOT include actual PYQs.
- Do NOT include programming/long-answer/HOTS questions in theory lecture practice.
- Frame original MCQ/Short Answer questions from exam-frequency concepts and examiner traps only.
- Every question must map to one concept/trap discovered in Section 4.

MCQ structure:
&lt;div class="mcq-box"&gt;
  &lt;b&gt;Q1.&lt;/b&gt; Question text?&lt;br&gt;
  &lt;ul class="options"&gt;
    &lt;li&gt;a) ...&lt;/li&gt;
    &lt;li&gt;b) ...&lt;/li&gt;
    &lt;li&gt;c) ...&lt;/li&gt;
    &lt;li&gt;d) ...&lt;/li&gt;
  &lt;/ul&gt;
  &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;
    &lt;ul class="options"&gt;
      &lt;li class="wrong"&gt;a) ... — reason why wrong&lt;/li&gt;
      &lt;li class="correct"&gt;b) ... ✓ — reason why correct&lt;/li&gt;
      ...
    &lt;/ul&gt;
  &lt;/details&gt;
&lt;/div&gt;

Short-answer structure:
&lt;div class="self-test-box"&gt;&lt;b&gt;Q4.&lt;/b&gt; Question&lt;br&gt;&lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;Full answer&lt;/details&gt;&lt;/div&gt;]



<h2 id="s7">7. Student Notes (Copy-ready)</h2>
[Concise notes — every concept highlighted by the exam-frequency analysis, written purely as concept notes (no PYQ wording) — in .key-box and .def-box; self-check questions in .self-test-box with &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;answer&lt;/details&gt;]

<h2 id="s8">8. Homework</h2>
[DYNAMIC HOMEWORK — match this concept and the question types the board actually uses for it
(self-generate the questions; never label them as previous-year or board questions):
- 2×1M (MCQ / very-short answer)
- 2×2M short answer
- 1×3M short answer (or, for a coding topic, a short program / output-prediction question)
- You MAY include one 3–5M long-answer or programming question (this concept supports it)
Dynamic rule: include a 5M long-answer or a programming question ONLY when this concept is genuinely
assessed that way; never force unsupported marks (e.g. a 5M) or question types. same concept — self-generated, never labelled as PYQ-pattern or board-style.
Mark difficulty with .critical/.high/.medium tag.
EVERY answer wrapped in &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt; inside .self-test-box or .mcq-box]

<h2 id="s9">9. Exam Tips</h2>
[5 specific tips as .tip-box — derived from examiner traps for THIS topic only — written as plain tips, no PYQ wording]

<h2 id="s10">10. Last-Minute Revision Cards</h2>
&lt;div class="card-grid"&gt;
[One .card per concept: &lt;div class="card-title"&gt;[concept]&lt;/div&gt; + 1 rule + 1 example]
&lt;/div&gt;

</div><!-- end .main-content -->
</body>
</html>

HARD OUTPUT RULES:
- Output ONLY the HTML document starting with &lt;!DOCTYPE html&gt;
- Do NOT wrap the output in markdown code fences.
- Do NOT add explanatory text before or after the HTML.
- Use ONLY content from the lecture topic ("Text file reading writing searching and counting").
- Do NOT include content from other topics.
- The exam-frequency input is private analysis only.
- Final visible HTML must NOT include:
    * actual board question text
    * year labels
    * section labels from papers
    * previous-paper metadata
    * the word "PYQ"
    * phrases like "previous year question", "PYQ-style", "PYQ-pattern", or "board-style"
- Every question, example, and practice item in the final HTML must be self-generated and concept-focused.
- Always finish the document completely through &lt;/html&gt;.
- If the answer becomes long, keep Section 3 complete first, then make Sections 7–10 compact instead of truncating.
- However many concepts the analysis surfaces, self-generate enough Section 3 and Section 6 checks to cover all important traps.
- Never dump real board questions to compensate for a large question pool.

ANSWER HIDING RULES:
- Section 3 concept checks: every answer must be hidden inside &lt;details&gt;&lt;summary&gt;▶ View Answer&lt;/summary&gt;...&lt;/details&gt;.
- Section 6 MCQs: options must be listed without .correct or .wrong before details.
- Section 6 MCQ answer analysis must appear only inside &lt;details&gt;.
- Section 6 short-answer questions: every answer must be hidden inside &lt;details&gt;.
- Section 7 self-check questions: every answer must be hidden inside &lt;details&gt;.
- Section 8 homework: every answer must be hidden inside &lt;details&gt;.
- The beforeprint JS already auto-opens all &lt;details&gt; for printing; never remove or skip this feature.

THEORY LECTURE STRUCTURE RULE:
- This theory lecture has no visible board-question discussion section.
- Sections 7–10 are allowed and required:
    Section 7: Student Notes
    Section 8: Homework
    Section 9: Exam Tips
    Section 10: Last-Minute Revision Cards

CODE SIZE RULE:
- Inline code must appear almost the same size as surrounding normal text.
- Do NOT use fixed 8.5pt size for all &lt;code&gt; elements.
- Use code { font-size:0.95em; } for inline code.
- Use pre { font-size:8.5pt; } for block code.
- Use pre code { font-size:inherit; } so code blocks remain compact.
- Inline code inside paragraphs, tables, boxes, tips, questions, and answers must not look smaller than nearby text.

BOX / CLASS USAGE RULES:
- Do NOT use .pyq-box or .pyq-meta in theory lectures.
- Use .mcq-box for MCQs.
- Use .self-test-box for short-answer checks and homework.
- Use .warn-box for examiner traps.
- Use .tip-box for exam tips.
- Use .def-box and .key-box for notes.
- Use .example-box for worked examples.
- Use .recall-box for exact output.

HTML TEMPLATE RULES:
- All generated content must go inside &lt;div class="main-content"&gt;.
- The &lt;nav class="toc-sidebar"&gt; is already present in the template.
- JS auto-builds TOC links from h2/h3 headings.
- Print buttons including Read Mode are already present in the template.
- Do NOT add print buttons again.
- Include the full CSS and JS exactly as given.