In Class 12 Computer Science, the focus shifts to more advanced programming concepts and practical applications. Building on the foundation laid in Class XI, you will explore topics like functions, exception handling, file handling, and data structures in greater depth. These concepts are essential for writing efficient and organized code, enabling you to solve more complex problems. Additionally, you will learn about databases, computer networks, and other essential topics that prepare you for higher-level studies in computer science or for real-world applications in technology. The comprehensive understanding of these topics will help you develop strong computational thinking and problem-solving skills, which are critical in today’s tech-driven world.
- Data Types: Different types of data like integers (
int
), floating-point numbers (float
), strings (str
), and booleans (bool
).Example:
pythonage = 18 # int
price = 19.99 # float
name = "Alice" # str
is_student = True # bool
- Variables: Names assigned to data stored in memory.
Example:
pythonx = 5
- Operators: Symbols used to perform operations on variables and values.
- Arithmetic operators (
+
,-
,*
,/
) - Comparison operators (
==
,!=
,>
,<
) - Logical operators (
and
,or
,not
)
Example:
pythonresult = 5 + 3 # Output:
8
is_equal = (5 == 3) # Output: False
- Arithmetic operators (
- Control Flow: You learned how to control the flow of execution in a Python program using:
- if, elif, else statements for decision-making.
Example:
pythonage = 18
if age >= 18:
print("You can vote!")
else:
print("You cannot vote.")
- Loops like
for
andwhile
to repeat actions.Example:
pythonfor i in range(5):
print(i) # Output: 0, 1, 2, 3, 4
- if, elif, else statements for decision-making.
- Functions: Blocks of code that perform a specific task and can be reused.
Example:
pythondef greet(name):
print(f"Hello, {name}!")
greet("Alice") # Output: Hello, Alice!
Functions
A function in Python is a block of code that only runs when it is called. Functions are useful because they allow code reusability and better organization.
Types of Functions
- Built-in Functions: These are functions that Python provides out of the box, such as
print()
,len()
,max()
, etc.Example:
pythonprint(len("Hello")) # Output: 5
- Functions Defined in a Module: These functions are not part of the core Python language but come from external libraries or modules such as
math
,random
, etc.Example:
pythonimport math
print(math.sqrt(16)) # Output: 4.0
- User-defined Functions: Functions created by users to perform specific tasks. These functions are written using the
def
keyword.Example:
pythondef greet(name):
return f"Hello, {name}!"
Creating User-defined Functions
A user-defined function is created using the def
keyword, followed by the function name, parentheses ()
, and a colon :
. Inside the function, you can write the logic that defines what the function does.
Arguments and Parameters
- Positional Parameters: These are parameters passed in the correct positional order.
python
def add(a, b):
return a + b
print(add(2, 3)) # Output: 5
- Default Parameters: These are parameters with default values.
python
def greet(name="Guest"):
return f"Hello, {name}!"
print(greet()) # Output: Hello, Guest!
Function Returning Value(s)
A function can return a result using the return
statement. You can also return multiple values as a tuple.
Example:
def add_subtract(a, b):
return a + b, a - b
result = add_subtract(5, 3)
print(result) # Output: (8, 2)
Flow of Execution
The flow of execution in a Python program starts at the top and moves downward. When a function is called, the control goes to the function, and once it completes, the control returns to the point where it was called.
Scope of a Variable
- Local Scope: Variables defined inside a function. These variables are not accessible outside the function.
- Global Scope: Variables defined outside all functions. These variables are accessible throughout the program.
Example:
x = 10 # Global variable
def test():
y = 5 # Local variable
print(x, y)
test() # Output: 10 5
Exception Handling
Exception handling is used to manage errors and exceptions in Python so that the program doesn’t crash when encountering errors.
- try-except-finally: Used to handle exceptions.
- try: Block of code that may raise an exception.
- except: Block of code to handle the exception.
- finally: Code that will run no matter what (used for cleanup).
Example:
try:
x = int(input("Enter a number: "))
except ValueError:
print("That's not a valid number!")
finally:
print("Execution finished")
Introduction to Files
Files are used for persistent storage. Python allows us to work with three types of files:
- Text File: Stores data in human-readable text form.
- Binary File: Stores data in binary (0s and 1s).
- CSV File: Comma Separated Values, used for storing tabular data.
Working with Text Files
- File Open Modes:
'r'
: Read mode'w'
: Write mode'a'
: Append mode'r+'
: Read and write mode'a+'
: Append and read mode
- Opening a File:
python
file = open('example.txt', 'r')
- Reading from a File:
python
content = file.read() # Reads the entire file
- Writing/Appending to a File:
python
file.write("Hello World!") # Write to the file
- Closing a File:
python
file.close()
- Using ‘with’ to open files:
python
with open('example.txt', 'r') as file:
content = file.read()
Binary Files
Binary files contain data in a format that is not human-readable. You can use the pickle
module for working with binary files.
- Opening Binary Files:
python
with open('data.dat', 'wb') as file:
# Writing binary data
- Using
pickle
Module:pythonimport pickle
with open('data.dat', 'wb') as file:
pickle.dump(data, file) # Write binary data
CSV Files
CSV files store tabular data in plain text. The csv
module is used to work with CSV files in Python.
- Reading and Writing CSV Files:
python
import csv
with open('data.csv', 'w', newline='') as file:
writer = csv.writer(file)
writer.writerow(['Name', 'Age'])
writer.writerows([['Alice', 23], ['Bob', 25]])
Data Structures: Stack
A stack is a data structure that follows the Last In, First Out (LIFO) principle. You can implement a stack using a list in Python.
- Operations on Stack:
- Push: Add an element to the stack.
- Pop: Remove the top element from the stack.
Example:
stack = []
stack.append(10) # Push
stack.pop() # Pop
Unit II: Computer Networks
Evolution of Networking
- ARPANET: The first network that led to the development of the Internet.
- NSFNET: A network created by the National Science Foundation, which contributed to the growth of the Internet.
Data Communication Terminologies
- Sender: The device that sends the message.
- Receiver: The device that receives the message.
- Message: The data being sent.
- Communication Media: The path through which data travels (wired or wireless).
- Bandwidth: The capacity of a communication medium to carry data.
Transmission Media
- Wired:
- Twisted Pair Cable: Commonly used for telephone lines.
- Coaxial Cable: Used for cable television.
- Fiber Optic Cable: High-speed transmission using light signals.
- Wireless:
- Radio Waves: Used for mobile communication.
- Microwaves: Used for satellite communication.
- Infrared Waves: Used for short-range communication.
Network Devices
- Modem: Converts digital signals to analog for transmission over telephone lines.
- Router: Directs data between networks.
- Switch: Connects devices within a network.
- Gateway: Connects different types of networks.
Network Protocols
- HTTP: Protocol used for transmitting web pages.
- FTP: Protocol for file transfers.
- TCP/IP: Protocols used for communication over the Internet.
Unit III: Database Management
Database Concepts
- Database: An organized collection of data.
- Relational Database: A database that organizes data into tables.
Keys in a Database
- Primary Key: A unique identifier for each record.
- Foreign Key: A field in one table that links to a primary key in another table.
Structured Query Language (SQL)
SQL is used to manage and manipulate relational databases.
- Basic SQL Commands:
CREATE DATABASE
to create a database.CREATE TABLE
to create a table.INSERT
to add records.SELECT
to retrieve records.UPDATE
to modify records.DELETE
to remove records.
Example:
CREATE TABLE Students (
ID INT PRIMARY KEY,
Name VARCHAR(50),
Age INT
);
INSERT INTO Students (ID, Name, Age) VALUES (1, 'Alice', 20);
Python-SQL Connectivity
You can connect Python to a SQL database using modules like mysql.connector
.
- Steps:
- Establish a connection using
connect()
. - Create a cursor using
cursor()
. - Execute SQL queries using
execute()
. - Fetch results using
fetchall()
orfetchone()
.
- Establish a connection using
Example:
python
import mysql.connector
conn = mysql.connector.connect(host='localhost', user='root', password='password', database='school')
cursor = conn.cursor()
cursor.execute("SELECT * FROM Students")
rows = cursor.fetchall()
for row in rows:
print(row)
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