UNIT1 - Programming
Week [10] –Programming Paradigms
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Lesson Learning Outcome
Pass
Merit
Distinction
LO2 Explain the characteristics of procedural, objectoriented and event driven programming, conduct an
analysis of a suitable Integrated Development Environment
(IDE)
P2 Give explanations of what M2 Analyse the common
procedural, object-oriented
features that a developer has
event driven paradigms are; access to in an IDE.
their characteristics and
relationship between them.
D2 Critically evaluate the
source code of an
application which
implements the program
paradigms, in terms of the
code structure and
characteristics.
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What is a Programming Paradigm?
▪ Programming paradigm is a style of programming which has characteristic
features.
▪ One can say these are the foundations on which programming languages are
designed and implemented.
▪ Some languages can be classified into multiple paradigms.
▪ Some paradigms are concerned mainly based on execution model of the
language.
▪ Other paradigms are concerned mainly with the way that code is organized.
▪ Yet others are concerned mainly with the style of syntax and grammar.
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Common Programming Paradigms
Imperative Programming (Procedural Paradigm)
Object Oriented Programming
Event Driven Programming
Declarative Programming
Logic Programming
Functional Programming
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Imperative Programming
▪ Imperative = Procedural = Structured Programming
▪ Computer use reusable memory
▪ Programs runs by changing the state of the machine via Assignment
▪ Control flow is explicit, uses Sequence, Selection, Repetition
▪ These can be more efficiently translated to machine language
▪ Structured Programming is a refined imperative style with 2 added
features
Fortran, Algol,
▪ No GOTOs
▪ Variables have lexical scope due to modules
Pascal, Basic, C
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Object Oriented Programming
▪ Programs are represented as a Group of Objects.
▪ Objects exhibit their own behaviour.
▪ In imperative style Data are Passive, Procedures are Active.
▪ O-O paradigm, data is combined with procedures to give objects.
For example in the imperative paradigm, one would write a procedure which prints the various
kinds of object in the program. In the O-O paradigm, each object has a print-method, and you "tell"
an object to print itself.
▪ Objects are grouped in Classes.
▪ Classes are arranged in a Hierarchy –
Sub classes inherit features from Super classes
Simula 67, Smalltalk, java, C++,
C# , Modula 3, Ruby, Python
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Declarative Programming
▪ Also called Non Imperative or
Non Procedural
▪ Control Flow is implicit
▪ Programmer states only what the
result should look like, not how to
obtain it.
SELECT Name, Salary
FROM Employee
WHERE DepName = ‘Sales’
ORDER BY Salary DESC
No Loops
No Selections
▪ SQL – Structured Query Language No Assignments
is good example for this
NO ALGORITHMS
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Logic Programming
▪ This is also Declarative Programming
▪ What is known about the domain is defined as
▪ Facts
▪ Inference Rules
▪ Solution is found by the Interpreter by
▪ Unification – Principle of substitution
▪ Backtracking – Return to prior step and continue
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PROLOG - Example
/* Some rules */`
is_digesting(X,Y)
:-
just_ate(X,Y).
is_digesting(X,Y)
:-
just_ate(X,Z), is_digesting(Z,Y).
/* Some facts */
just_ate(mosquito,blood(john)).
just_ate(frog,mosquito).
just_ate(stork,frog).
? is_digesting (Who, mosquito)
Who = frog
Who = stork
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Functional Programming
▪ This is also Declarative Programming
▪ No Variables and therefore No States
▪ Everything is defined as Functions
▪ No state changes – Immutable
▪ Thus preserve Referential Transparency – Guarantees
that a function return the same result for the same
parameters in each and every call,
▪ LISP and Haskel are functional language examples.
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Event-driven Programming
Event-driven programming is a
programming paradigm in which
the flow of program execution is
determined by events - for
example a user action such as a
mouse click, key press, or a
message from the operating
system or another program.
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Key Terminology
The event source is an
object on which the
event occurs. Source
provides information
of the occurred event
to it's handler via an
Event object.
This provides
information of the
occurred event.
The listener is in effect
a loop which waits for
an event to occur.
A collection of routines
that defines the
responses to the
Event(S). In some
implementations
Listener and Handler is
the same
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How to create an Event-driven Program
▪ Step 1: The first step in developing an event-driven
program is to write a series of subroutines, or methods,
called event-handler routines.
▪ Step 2: The second step is to bind event handlers to
events so that the correct function is called when the event
takes place.
Graphical editors combine the first two steps: double-click on a
button, and the editor creates an (empty) event handler
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How to create an Event-driven Program
▪ Step 3: Final step is to write the main loop. Most eventdriven programming environments already provide this
main loop, so it need not be specifically provided by the
application programmer.
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New Trends in Languages
▪ Based on the main features we call it an Imperative, Object Oriented or
Functional language.
▪ Very few languages implement a paradigm 100%. When they do, they are
pure.
▪ It is incredibly rare to have a “pure OOP” language or a “pure functional”
language.
▪ A lot of languages will facilitate programming in one or more paradigms.
▪ In Scala you can do imperative, object-oriented, and functional
programming quite easily
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Lesson Summary
▪ What is a Programming Paradigm
▪ Common Programming Paradigms
▪ Imperative Programming
▪ Object Oriented Programming
▪ Declarative / Logic Programming
▪ Functional Programming
▪ Event-driven Programming
▪ New trends in languages
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