Operating System Notes
Complete, Structured & Easy-to-Understand Guide
Topics Covered
Topic 1 : Classes and Objects
Topic 2 : Encapsulation
Topic 3: Inheritance
Topic 4: Polymorphism
Topic 5: Abstraction
Topic 6: Constructors
Topic 7: Overloading vs Overriding
Topic 8: Static Members(Static Variables, Static Methods, Static Blocks)
Topic 9: Memory Management (Stack, Heap, new/delete, Garbage Collection)
Topic 10: Exception Handling
Topic 11: Access Modifiers
Topic 12: Friend Function & Friend Class (C++)
Key Concepts & Definitions
Examples & Diagrams
Short Notes for Quick Revision
Created By:
Aurin Nath, Akash Garg
Description:
These notes provide a clear and concise explanation of essential Operating System concepts for
students, beginners, and learners who are preparing for exams or interviews. The content is topic-
wise, easy to follow, and suited for both quick revision and in-depth understanding.
, Topic 1 : Classes and Objects
What is a Class?
A class is a blueprint or a template that defines:
Properties (variables)
Behaviors (methods/functions)
Example (Java):
Class Student {
String name;
Int age;
Void study() {
System.out.println(“Student is studying”);
}
}
This means that auditory end organs are capable of changing their sensory functions and reacting
correspondingly to different conditions. Sandhills' ecosystem. It does not occupy memory until an
object is created.
What is an Object?
An object is a real-world entity created from a class.
It occupies memory and can use the variables/methods inside the class.
Example:
Student s1 = new Student();
S1.name = “Aurin”;
S1.age = 20;
S1.study()
, Key Points
Class → Definition
Object → Instance of a class
Many objects can be created from one class. Objects interact using methods Memory allocation
happens only when the object is created
Topic 2 : Encapsulation
Why Encapsulation?
To protect the data, so nobody can change it directly.
Example:
You cannot directly withdraw money from a bank database.
You must use proper methods like withdraw() or deposit().
Key Features of Encapsulation
1. Data Hiding
Make variables private
Cannot be accessed directly from outside
2. Controlled Access
Use getters and setters
Only allow safe modification
3. Enhances Security
Sensitive data protected Validations possible, for example – age cannot be negative.
Example (Java)
Complete, Structured & Easy-to-Understand Guide
Topics Covered
Topic 1 : Classes and Objects
Topic 2 : Encapsulation
Topic 3: Inheritance
Topic 4: Polymorphism
Topic 5: Abstraction
Topic 6: Constructors
Topic 7: Overloading vs Overriding
Topic 8: Static Members(Static Variables, Static Methods, Static Blocks)
Topic 9: Memory Management (Stack, Heap, new/delete, Garbage Collection)
Topic 10: Exception Handling
Topic 11: Access Modifiers
Topic 12: Friend Function & Friend Class (C++)
Key Concepts & Definitions
Examples & Diagrams
Short Notes for Quick Revision
Created By:
Aurin Nath, Akash Garg
Description:
These notes provide a clear and concise explanation of essential Operating System concepts for
students, beginners, and learners who are preparing for exams or interviews. The content is topic-
wise, easy to follow, and suited for both quick revision and in-depth understanding.
, Topic 1 : Classes and Objects
What is a Class?
A class is a blueprint or a template that defines:
Properties (variables)
Behaviors (methods/functions)
Example (Java):
Class Student {
String name;
Int age;
Void study() {
System.out.println(“Student is studying”);
}
}
This means that auditory end organs are capable of changing their sensory functions and reacting
correspondingly to different conditions. Sandhills' ecosystem. It does not occupy memory until an
object is created.
What is an Object?
An object is a real-world entity created from a class.
It occupies memory and can use the variables/methods inside the class.
Example:
Student s1 = new Student();
S1.name = “Aurin”;
S1.age = 20;
S1.study()
, Key Points
Class → Definition
Object → Instance of a class
Many objects can be created from one class. Objects interact using methods Memory allocation
happens only when the object is created
Topic 2 : Encapsulation
Why Encapsulation?
To protect the data, so nobody can change it directly.
Example:
You cannot directly withdraw money from a bank database.
You must use proper methods like withdraw() or deposit().
Key Features of Encapsulation
1. Data Hiding
Make variables private
Cannot be accessed directly from outside
2. Controlled Access
Use getters and setters
Only allow safe modification
3. Enhances Security
Sensitive data protected Validations possible, for example – age cannot be negative.
Example (Java)
