Programming paradigms (procedural, low-level / assembly and object-oriented), the need for and characteristics of different levels of programming language, and the core principles of object-oriented programming: classes, objects, methods, attributes, encapsulation, inheritance and polymorphism.

What this dot point is asking

OCR wants the characteristics of the procedural, low-level and object-oriented paradigms, why languages exist at different levels (high-level versus low-level), and precise definitions of the OOP principles, classes, objects, methods, attributes, encapsulation, inheritance and polymorphism, with examples. Expect a definition-with-example question on OOP and a high-level versus low-level comparison.

The answer

Paradigms and language levels

Classes, objects, methods and attributes

class BankAccount:
    def __init__(self, holder, balance):
        self.__holder = holder      # private attribute
        self.__balance = balance

    def deposit(self, amount):      # method
        if amount > 0:
            self.__balance += amount

    def get_balance(self):          # accessor / getter
        return self.__balance

account = BankAccount("Asha", 100)  # object (instance)
account.deposit(50)
print(account.get_balance())        # 150

Encapsulation, inheritance and polymorphism

class Shape:
    def area(self):
        return 0

class Circle(Shape):            # inheritance
    def __init__(self, r):
        self.r = r
    def area(self):             # polymorphism (override)
        return 3.14159 * self.r ** 2

class Rectangle(Shape):
    def __init__(self, w, h):
        self.w, self.h = w, h
    def area(self):
        return self.w * self.h

for s in [Circle(2), Rectangle(3, 4)]:
    print(s.area())             # 12.566..., 12

Examples in context

Game engines model entities (players, enemies, items) as objects in an inheritance hierarchy, using polymorphism so one update loop drives them all. Operating-system device drivers and embedded firmware are often written in low-level code for direct hardware control. Procedural style still suits short scripts and numerical routines. OCR ties this to the detailed OOP programming techniques in Component 02, where you read and write class definitions, and to the trade-offs between paradigms when designing the Programming Project.

Try this

Q1. State the difference between a class and an object. [2 marks]

• Cue. A class is a template defining attributes and methods; an object is a specific instance of that class with its own attribute values.

Q2. Explain how encapsulation protects an object's data. [2 marks]

• Cue. Attributes are kept private and can be changed only through public methods (setters) that can validate input, preventing invalid states from outside code.

Q3. State one situation where a low-level language is more appropriate than a high-level one. [1 mark]

• Cue. Where direct hardware control or maximum speed and memory efficiency are needed, for example a device driver or embedded firmware.