Download Classification of Programming Languages Based on How They

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Classification of
Programming Languages
Based on How They
Derive Machine Code
Compilers vs. Interpreters
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Compiler – computer program that transforms source code written
in one computer language to equivalent code in another
language
• most commonly it is translation from a high-level to a machine lang.
• compiled languages: C, C++, Eiffel, Fortran, Crystal, …
A compiler must translate an entire program
into machine code before
the program can be executed.
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COMMERCIAL COMPILER
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http://www.slideshare.net/darokoblog/an-introduction-to-java-programming-languageforbeginnersjava-programming-tutorials
Compilers vs. Interpreters (cont.)
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Interpreter – program that directly executes instructions written in a
programming or scripting language without compiling
them into a machine language
• interpreted languages: JavaScript, PHP, Ruby, Python, …
An interpreter translates one program statement at a time,
executing a statement as soon as it is translated (‘on the fly’).
Compilers vs. Interpreters (cont.)
Once compiled, code
is immediately ready
to run.
Can be optimized for a
CPU, to run faster.
Difficult to ‘decipher’
what the source code
was from executable.
Code needs to be
compiled separately
for different CPUs.
Compiled code
cannot be optimized
‘on the fly’.
Code cannot be run
unless compiled.
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The same source
code can be ‘run’ on
all machines.
User must install
proper interpreter.
Can test code right
away, without having
to compile it.
Have to go through
‘on the fly’ translation
every time.
Can observe
program execution
‘line by line’.
Source, not machine
code, gets
disseminated.
Compilers vs. Interpreters (cont.)
Is Java
a compiled or an interpreted
language ?!?!
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Classification of
Programming Languages
Based on
Programming/Coding Philosophy
Procedural vs. Object Oriented Programming
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Procedure-Oriented - style of programming in which individual
operations used in a program are grouped
Programming
into logical units called procedures / functions
• main program can be viewed as a sequence of
procedure calls
• operations / procedures are executed in the order
of their appearance in the main program
• procedures from one program often CANNOT be
reused in another program
Procedural vs. Object Oriented Programming (cont.)
Example [ C program ]
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Procedural vs. Object Oriented Programming (cont.)
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Object-Oriented - style of programming in which both data and the
functions that operate on that data are combined/
Programming
encapsulated into a single program entity called
(OOP)
object
• thinking in OOP manner involves envisioning program
components as objects (class instances) that are similar
to concrete objects in the real world
Procedural vs. Object Oriented Programming (cont.)
Object-Oriented Programming (OOP) Advantages
 Ease of comprehension.
 Ease of modification and maintenance.
 Ease of code re-use.
Object-Oriented Programming (OOP) Disadvantages
 Requires (initially) longer code/software design time.
 Could lead to larger and more complex programs.
 Could produce slower programs.
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Procedural vs. Object Oriented Programming (cont.)
 C, Fortran, Pascal, …
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 Eiffel, Ruby, Python, …
Java is 99% OOP language.
Object Oriented Programming
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OOP Basics
Class - a blueprint / template for objects
• class definition describes what attributes its objects will have and
what methods those objects will be able to do
You can use the same class as a template to make
(instantiate) many objects.
Object Oriented Programming (cont.)
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Object - a concrete instance of a classes
• you can create objects from classes that you write and from classes
written by other programmers, including Java’s creators
Object Oriented Programming (cont.)
https://engamrtarek.wordpress.com/2013/12/29/java-the-three-oop-principles-encapsulationinheritance-polymorphism/
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Object Oriented Programming (cont.)
Encapsulation - mechanism that binds together code and its
respective data - all methods and data related
to an object are stored within the object/class
• ideally, object data should be accessible only through
object methods
• serves as a ‘protective wrapper’ that shields the
code and data from outside interference and misuse
• key enablers of encapsulation: public and private
access modifiers
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Object Oriented Programming (cont.)
Example [ encapsulation ]
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Object Oriented Programming (cont.)
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Inheritance - ability to create classes that share the attributes and
methods of existing classes, but with more specific
features
• child/sub class inherits all the members (fields, methods and
nested classes) from its parent/super class
• enables faster code development, and allows for better code
organization and minimization of duplicate code
single inheritance
multilevel inheritance
hierarchical inheritance
Object Oriented Programming (cont.)
Example [ inheritance ]
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Object Oriented Programming (cont.)
Example [ inheritance ]
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Object Oriented Programming (cont.)
Polymorphism - allows actions to act differently based on
either which object is performing the action or
the object the action is being performed on
• method is able to deal with different types of inputs
• polymorphism enables programmers to create code
that is easier to understand and reuse
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Object Oriented Programming (cont.)
Example [ polymorphism ]
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Java
Is Java a pure
OO language?!
- for a language to be pure OO language,
it must:
• support Encapsulation
• support Inheritance
• support Polymorphism
• all predefined types must be Objects
• all user defined types must be Objects
• operations performed on objects must be
through methods exposed at the objects
Java’s primitive data
types are not objects:
int, char, float
Java static methods and
variables can be accessed
directly from the class,
without the need to
create an instance.
Java is 99% OOP.
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Java (cont.)
Is Java compiled or interpreted language?!
Java combines the use of a compiler and an interpreter.
Java compiler translates Java source code into (intermediate-level)
Java bytecode – ‘machine language’ for Java Virtual Machine (JVM) .
Java VM (interpreter) reads Java bytecode and executes it on a
specific machine.
Win JVM
Mac JVM
MyProgram.java
MyProgram.class
Unix JVM
Java (cont.)
Java is Platform - bytecode (x.class) generated after compilation
of a java source file can be executed on any
Independent
platform
(Cross-Platform)
• bytecode generated on Windows is the same as the
Language
bytecode generated on Mac
• note, however, that JVMs are platform dependant !!!
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Java (cont.)
Java and the Internet
http://java.meritcampus.com/core-java-topics/Creation-Of-Java-As-Platform-Independence-WORA
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Java (cont.)
Java History
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