Procedural vs OOP, Classes, Objects and OOP Principles (ISC Class 11 Computer Science)

Understand Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP

class Rect {
    int l, b;                      // attributes
    int area() { return l * b; }   // behaviour
}
Rect r = new Rect();   r.l = 5;  r.b = 3;
System.out.println(r.area());     // 15

Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP: key facts

Class and object

Class = blueprint (attributes + methods) | Object = instance created with new

Relationship.

Four principles

• •Abstraction
• •Encapsulation
• •Inheritance
• •Polymorphism

Core of OOP.

Creating an object

• •ClassName obj = new ClassName();
• •obj.method();
• •obj.attribute

Syntax.

How to answer Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP questions

1. 1Name the class and list attributes and behaviours.
2. 2Write the class with variables and methods.
3. 3Create objects with new and set or pass values.
4. 4Trace the output using each object's own data.

Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Tricks to remember Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP

Short memory aids. Say each one aloud once, then use it on a question the same day.

• A-E-I-P

  Abstraction, Encapsulation, Inheritance, Polymorphism.

  Use it when: Principles.

• Class = noun type, object = instance

  Class is the type; object is a particular one.

  Use it when: Definition.

• private hides

  Encapsulation uses private data and public methods.

  Use it when: Data hiding.

Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Rect r1 = new Rect(); r1.l = 5; r1.b = 3;
Rect r2 = new Rect(); r2.l = 4; r2.b = 6;
System.out.println(r1.area() + " " + r2.area());
r2.l = 10;
System.out.println(r1.area() + " " + r2.area());

Where students lose marks in Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP

The slips examiners see most often, and what to write instead.

• ✗Mistake: Defining an object as a class

  Confusing blueprint and instance.

  Wrong working

  An object is a template

  Right working

  An object is an instance of a class

  ✓Do this: Class = template.

  Usually costs: 1-2 marks.

• ✗Mistake: Using one object's data for another

  Sharing assumption.

  Wrong working

  r1.area() becomes 60

  Right working

  r1.area() stays 15

  ✓Do this: Each object has its own copy.

  Usually costs: 2 marks.

• ✗Mistake: Describing encapsulation as hiding code

  Common slip.

  Wrong working

  Encapsulation hides the code

  Right working

  Binds data with methods and hides the data

  ✓Do this: Data hiding.

  Usually costs: 1 mark.

Practice questions on Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQBoard level

   Which of the following is an object-oriented programming language?
   (a) C (b) Java (c) Assembly (d) FORTRAN 66

   Hint

   Classes and objects.

   Answer

   (b) Java

2. Q2 · 2 marks · Short answerBoard level

   State two differences between procedural and object oriented programming. (2 marks)

   Hint

   Focus; data.

   Answer

   Procedural programming focuses on procedures with global data; OOP focuses on objects that bind data and methods and can hide data.

3. Q3 · 5 marks · Long answerHarder board level

   Write a class Student with attributes name and marks and a method that returns "Pass" if marks are 40 or more, otherwise "Fail". State the output for marks 40 and 39. (5 marks)

   Hint

   Return a String.

   Answer

   class Student { String name; int marks; String result() { if (marks >= 40) return "Pass"; else return "Fail"; } } For marks 40 the output is Pass; for 39 it is Fail.

4. Q4 · 3 marks · Short answerHarder board level

   Given class Counter { int c; void inc() { c = c + 1; } } write the output: Counter a = new Counter(); Counter b = new Counter(); a.inc(); a.inc(); b.inc(); System.out.println(a.c + " " + b.c); (3 marks)

   Hint

   Each object has its own c.

   Answer

   a.c = 2 and b.c = 1: output 2 1.

5. Q5 · 4 marks · Short answerHOTS / competency

   A company wants Employee data (salary) to be changed only through a method that rejects negative values. Explain which principle is used, what access specifier is given to salary, and write the method. (4 marks)

   Hint

   private and a setter.

   Answer

   Encapsulation (data hiding): declare salary private and provide public void setSalary(double s) { if (s >= 0) salary = s; } so that negative values cannot be stored.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Class is?Show answer

   A blueprint for objects.

2. 2.Object is created by?Show answer

   The new operator.

3. 3.Data hiding is?Show answer

   Encapsulation.

4. 4.Inheritance gives?Show answer

   Reuse.

5. 5.Polymorphism means?Show answer

   One name, many forms.

Procedural versus Object Oriented Programming: Classes, Objects and the Principles of OOP: frequently asked questions