Padikam lessons

ORIGINAL STUDY COMPANION PADIKAM CLASS 12 | SCIENCE / ELECTIVE Computer Science CBSE / NCERT core lessons | Academic year 2026-27 11 chapter lessons Quick explanations, core points, exam practice and chapter-specific notation in one consistent format. Padikam explanations are independently written. Official textbooks are used as the coverage map, chapter sequence and terminology reference. PADIKAM | CBSE NCERT CLASS 12 1

Contents 01 Python Revision and Functions 02 Exception Handling 03 Text Files 04 Binary Files 05 CSV Files 06 Stack 07 Computer Networks 08 Network Protocols and Web Services 09 Relational Databases 10 SQL 11 Python-SQL Connectivity and Project Study rhythm Read the quick explanation, recall the core points aloud, then answer the prompts without looking back. Use the official textbook links for full prescribed readings, activities and diagrams. Textbook and verification links

1. https://cbseacademic.nic.in/web_material/CurriculumMain27/SecPart2/Computer_Science_SecP2_2026-27.pdf
2. https://ncert.nic.in/textbook.php?lecs1=0-13
3. https://cbseacademic.nic.in/new-resources-srsec.html PADIKAM | CBSE NCERT CLASS 12 2

CHAPTER 01 Python Revision and Functions Quick understanding Functions organise Python logic through parameters, return values, scope and predictable flow of execution. Core points Check your learning Positional and default parameters follow declaration Explain the central idea of Python rules. Revision and Functions in your own words. Return sends a result; print only displays. Apply one idea from Python Revision Local and global names must be traced separately. and Functions to a textbook-style example or source. Code pattern def total(price, qty=1): return price * qty amount = total(125.0, 3) One-line recall Positional and default parameters follow declaration rules. PADIKAM | CBSE NCERT CLASS 12 3

CHAPTER 02 Exception Handling Quick understanding Exception handling separates normal logic from controlled responses to runtime problems. Core points Check your learning Catch specific exceptions where possible. Explain the central idea of Exception Handling in your own words. else runs after a successful try; finally runs for cleanup. Apply one idea from Exception Handling to a textbook-style example or source. Do not hide errors with an empty broad handler. Code pattern try: value = int(input("Number: ")) except ValueError: print("Enter an integer") else: print(value * value) One-line recall Catch specific exceptions where possible. PADIKAM | CBSE NCERT CLASS 12 4

CHAPTER 03 Text Files Quick understanding Text-file programs open a path in a chosen mode, read or write strings and close the resource reliably. Core points Check your learning The with statement closes the file automatically. Explain the central idea of Text Files in your own words. read, readline and readlines return different shapes. Apply one idea from Text Files to a seek and tell work with the file position. textbook-style example or source. Code pattern with open("notes.txt", "r", encoding="utf-8") as file: for line in file: print(line.rstrip()) One-line recall The with statement closes the file automatically. PADIKAM | CBSE NCERT CLASS 12 5

CHAPTER 04 Binary Files Quick understanding Binary files preserve Python records through serialisation and require matching write and read logic. Core points Check your learning pickle.dump writes one object at the current position. Explain the central idea of Binary Files in your own words. Repeated load calls recover repeated stored objects until EOF. Apply one idea from Binary Files to a textbook-style example or source. Updates commonly rewrite records through a temporary file. Code pattern import pickle with open("students.dat", "wb") as file: pickle.dump({"roll": 7, "mark": 91}, file) One-line recall pickle.dump writes one object at the current position. PADIKAM | CBSE NCERT CLASS 12 6

CHAPTER 05 CSV Files Quick understanding CSV files exchange rows of text fields between programs and tabular tools. Core points Check your learning Use the csv module so quoting and delimiters are Explain the central idea of CSV Files in handled correctly. your own words. writerow writes one row; writerows writes many. Apply one idea from CSV Files to a textbook-style example or source. Convert numeric fields after reading because CSV values are text. Code pattern import csv with open("marks.csv", "w", newline="") as file: writer = csv.writer(file) writer.writerow(["Roll", "Mark"]) One-line recall Use the csv module so quoting and delimiters are handled correctly. PADIKAM | CBSE NCERT CLASS 12 7

CHAPTER 06 Stack Quick understanding A stack is a last-in first-out structure implemented in the syllabus with list operations. Core points Check your learning Push appends at the top. Explain the central idea of Stack in your own words. Pop must check underflow before removal. Apply one idea from Stack to a textbook- The top item is at the end when append and pop are style example or source. used. Code pattern stack = [] stack.append("A") if stack: item = stack.pop() One-line recall Push appends at the top. PADIKAM | CBSE NCERT CLASS 12 8

CHAPTER 07 Computer Networks Quick understanding Networks share data and services through media, devices, addressing and agreed protocols. Core points Check your learning LAN, MAN and WAN describe different scopes. Explain the central idea of Computer Networks in your own words. Switches, routers, modems and access points perform different roles. Apply one idea from Computer Networks to a textbook-style example or source. Bandwidth and data transfer rate use bit-based units. Equation and notation Data transfer rate = Data transferred / Time SYMBOLS AND UNITS Data transferred: bit (b) or byte (B), as stated Time: second (s) Transfer rate: bit s⁻¹, commonly kbps, Mbps or Gbps One-line recall LAN, MAN and WAN describe different scopes. PADIKAM | CBSE NCERT CLASS 12 9

CHAPTER 08 Network Protocols and Web Services Quick understanding Protocols define communication rules, while internet services build application behaviour on those rules. Core points Check your learning TCP and IP handle reliable transport and Explain the central idea of Network internetwork routing roles. Protocols and Web Services in your own words. HTTP/HTTPS support web transfer; SMTP and POP/IMAP support email. Apply one idea from Network Protocols and Web Services to a textbook-style URLs, domains and DNS help locate services. example or source. One-line recall TCP and IP handle reliable transport and internetwork routing roles. PADIKAM | CBSE NCERT CLASS 12 10

CHAPTER 09 Relational Databases Quick understanding A relational database stores rows in linked tables whose keys and constraints preserve meaning. Core points Check your learning A primary key is unique and not null. Explain the central idea of Relational Databases in your own words. A foreign key references a candidate key in another relation. Apply one idea from Relational Databases to a textbook-style example Degree counts columns; cardinality counts rows. or source. One-line recall A primary key is unique and not null. PADIKAM | CBSE NCERT CLASS 12 11

CHAPTER 10 SQL Quick understanding SQL creates, queries and updates relational data with filters, functions, grouping and joins. Core points Check your learning WHERE filters rows before GROUP BY. Explain the central idea of SQL in your own words. Aggregate functions normally ignore NULL values except COUNT(*). Apply one idea from SQL to a textbook- style example or source. JOIN conditions prevent meaningless Cartesian combinations. Code pattern SELECT Department, AVG(Salary) AS AvgSalary FROM Employee GROUP BY Department HAVING AVG(Salary) > 50000; One-line recall WHERE filters rows before GROUP BY. PADIKAM | CBSE NCERT CLASS 12 12

CHAPTER 11 Python-SQL Connectivity and Project Quick understanding A database application connects Python to MySQL, executes parameterised statements, processes results and commits intentional changes. Core points Check your learning Use placeholders instead of building SQL from input Explain the central idea of Python-SQL strings. Connectivity and Project in your own words. fetchone and fetchall consume result rows. Apply one idea from Python-SQL Close cursors and connections and handle rollback Connectivity and Project to a textbook- when needed. style example or source. Code pattern cursor.execute("SELECT Name FROM Student WHERE RollNo=%s", (roll,)) row = cursor.fetchone() connection.commit() One-line recall Use placeholders instead of building SQL from input strings. PADIKAM | CBSE NCERT CLASS 12 13