20.1 Programming Paradigms

## Imperative (procedural) programming language
Programs with an explicit sequence of commands that update the program state, with or without procedure calls
- Imperative languages use variables
- … which are changed using (assignment) statements
- … they rely on a method of repetition / iteration.
- The statements provide a sequence of commands for the computer to perform
- … in the order written / given
- … each line of code changes something in the program run.
## Declarative programming language
Programs that specify the desired result rather than how to get to it
- Instructs a program on what needs to be done instead of how to do it
- ... using facts and rules
- … using queries to satisfy goals.
- Can be logical or functional
- Logical - states a program as a set of logical relations
- Functional – constructed by applying functions to arguments / uses a mathematical style
##### Low-level
Programs using the instruction set of a processor
## Object-Oriented Programming (OOP)
Programs using the concepts of class, inheritance, encapsulation and polymorphism
###### Instance
- an occurrence of an object // a specific object based on the class // an instantiation of a class.   
###### Inheritance
- the capability of defining a new class of objects that has all the attributes and methods from a parent class.
- Methods and properties / attributes contained in one class/ super class / base class
- Are made available to / reused by another class/ derived class
###### Polymorphism
- allows the same method to take on different behaviours depending on which class is instantiated // methods can be redefined for derived classes.   
###### Encapsulation
- putting properties and methods inside a class // ensures sensitive data is hidden from users by hiding values of a structured data object inside a class.
###### Getter
- method that is used to return the value of a property.   
######  Setter
- method that is used to update the value of a property.   
###### Properties
- the data items / attributes
- the data types // characteristics
- defined in a class
###### Methods
- the procedures/ functions / programmed instructions in a class / super class / base class
- … implementing the behaviours
- … that act on the properties / attributes

| *Program code example* | *Programming paradigm* |
| ------------------------------------------------------------ | ----------------------- |
| male(john). female(ethel). parent(john, ethel). | Declarative |
| FOR Counter = 1 TO 20 X = X * Counter NEXT Counter | Procedural / imperative |
| Start: LDD Counter INC ACC STO Counter | Low-level / assembly |
| public class Vehicle { private speed; public Vehicle() { speed = 0; } } | Object oriented / (OOP) |