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A BRIEF HISTORY OF OOP AND JAVA PROGRAMMING LANGUAGE

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Almost all major concepts of OOP, such as objects, classes, and inheritance ... A computer scientist, James Gosling, developed Oak for use in embedded consumer ... – PowerPoint PPT presentation

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Title: A BRIEF HISTORY OF OOP AND JAVA PROGRAMMING LANGUAGE


1
A BRIEF HISTORY OF OOP AND JAVA PROGRAMMING
LANGUAGE
  • Ziya Karakaya
  • Atilim University
  • Tel (312) 4602020 / 5345 Faks (312) 460 20
    37
  • E-posta ziya_at_atilim.edu.tr

2
History of Object-Oriented Programming Languages
  • Almost all major concepts of OOP, such as
    objects, classes, and inheritance hierarchies,
    were developed in the 1960s
  • Simula language, by Norwegian Computing Center
  • In the 1970s, Alan Kay developed Smalltalk
    language at Xerox PARC (the Palo Alto Research
    Center)
  • targeted to be understandable to people with no
    prior training in computer use
  • demonstrated by experiments conducted using
    children as programmers

3
History (contd)
  • Bjarne Stroustrup at Bell Labs who had learned
    Simula during his Ph.D. studies developed C as
    an extension of C
  • Later many other OOP languages were developed
    Eiffel, Objective-C, Actor, Object Pascal, etc.
  • Since 1986 (first OOPSLA conference) OOP is a
    mainstream player in the PL domain the rather
    than a revolutionary one.

4
Why Java ?
  • We will explore the OOP in the context of Java
    programming language.
  • OOP has been a hot topic for over a decade
  • Java has recently become the commonly perceived
    embodiment of object-oriented ideas

5
Java Programming Language
  • Java is a general purpose programming language
    that can be used to create almost any type of
    computer program.
  • Especially, it can be used to create programs
    intended for execution across the Internet.

6
The History of Java
  • It was named Oak in 1991 at Sun Microsystems.
  • A computer scientist, James Gosling, developed
    Oak for use in embedded consumer electronic
    applications, such as VCRs.
  • This development purpose has determined many of
    the characteristics of the language.
  • Size and reliability are key features.
  • The processors that run in embedded systems are
    very small and has very little memory. A program
    must be able to be translated into a very concise
    encoding.
  • Embedded systems should almost never fail.

7
  • Java has these features.
  • Pointers and goto statement were eliminated.
  • Exception-handling is enforced to handle the
    unexpected in a graceful fashion
  • Unfortunately, Java (or Oak) as a language for
    embedded consumer electronics did not materialize
    at that time!

8
Evolution of World Wide Web
  • World Wide Web was developed in the early 1990s
    by a small group of scientists at a research lab
    in Switzerland.
  • As a mean of quickly communicating research
    results to a physically far-flung set of
    colleagues.
  • To understand how Java fits into the WWW, one
    must understand about the concepts of clients and
    servers and the difference between server-side
    computing and client-side computing.

9
Client-Side Computing
  • The Internet is a classic example of a
    client/server system.
  • A person using the Internet works at his or her
    own computer, which runs an Internet-aware
    application, such as a Web browser. This is
    called the client system.
  • The client application communicates over the
    Internet with another computer. For example, a
    Web browser might request the information on a
    Web page stored on a distant computer.
  • This computer is the server computer.
  • The client computer then determines how to
    display this information to the user.

10
Client-Side Computing
  • In the past these programs are executed on the
    server computer. The client transmitted a
    request, and the server responded by executing a
    program and transmitting the result.
  • Several performance problems occur
  • There exists a delay between the moment when the
    client asks that a program be executed and the
    time the results are returned.
  • Server programs often deal with many clients at
    once, reducing performance.

11
Client-Side Computing
  • In client-side computing, rather than executing
    the program on the server side and transmitting
    the result, the server will transmit the program
    to the client.
  • The client will execute the program locally.
  • Advantages
  • Program run on a less heavily loaded system
  • Only delay is the time to transmit the program
    user interactions take place locally.

12
Bytecode Interpreter and Just In Time Compilers
  • Client many not know what type of machine the
    server is using.
  • The traditional concept of computer programs
    being translated into machine code for a specific
    machine will not work.
  • Java is translated into a device-independent
    bytecode.
  • This Bytecode is like a machine language for an
    imaginary machine, a Java-specific machine, or
    Java Virtual Machine (JVM)
  • Each computer that runs Java programs then
    processes these bytecodes into a form that works
    correctly on the current system.

13
Interpreters vs. JIT Compilers
  • The easiest scheme is to have an interpreter that
    reads and executes bytecodes one by one.
  • A better performance can be obtained by using a
    just-in-time (JIT) compiler.
  • This system takes the Java bytecodes and
    translates them into the machine code native to
    the client system.
  • These programs then run as fast as any compiled
    program created specifically for the client
    computer.

14
Security Issues
  • A program running on the client side could have
    full access to the client computer resources.
  • There is potential for such a program to do
    significant damage, such as erasing files from a
    hard drive.
  • Java programs use a security manager provided by
    the client.
  • It limits the actions that can be performed by
    the Java program provided by the server.
  • For example, no access to the file system or
    access to other machines across the Internet.

15
Specialization of Interfaces
  • The sequences of commands needed to perform
    graphical operations varies greatly from one
    machine to another.
  • The solution to this problem requires a careful
    coordination between the client and server
    computers.
  • Portions of a Java program originating on one
    machine, and other parts coming from the second.
  • The server program is structured in terms of
    generic classes, such as Window and Button.

16
  • Generic classes are the same regardless of the
    type of system on which the Java program is run.
  • When executed, these components create a peer
    component.
  • The peer component originates on the client
    system and is not part of the server program.
  • Thus, a button running on a PC will create a
    PC-Button peer, while the same program running on
    a Macintoch will create a Mac-Button peer.

17
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18
The White Paper Description
  • Java is a simple, object-oriented, network-savvy,
    interpreted, robust, secure, architecture
    neutral, portable, high-performance,
    multithreaded, dynamic language.
  • A buzzyword heavy description

19
Java is Simple
  • Simpler than C
  • No preprocessor.
  • Far fewer special cases.
  • No confusing features such as overloaded
    operators, independent functions, global
    variables, goto statement, structures, or
    pointers.
  • Augmented with a larger library of high-level
    development tools.

20
A Remark on Pointers
  • In many languages, there is a distinction between
    a value vs. a pointer to a value
  • Values are static, fixed-size entities
  • Pointers are dynamic quantities filled at
    run-time.
  • There are important reasons why object-oriented
    language should make heavy use of pointers.
  • Java does so, but implicitly. Everything is
    internally a pointer.
  • Elimination of this construct removes common
    errors, making it easier to construct reliable
    and correct programs.

21
Java is Object-Oriented
  • Java has no functions and no variables that can
    exist outside of class boundaries.
  • Thus, all Java programs must be built out of
    objects.
  • C and Object Pascal (Delphi) combine OO
    features on top of an existing,
    non-object-oriented language.
  • Programmers can continue working in old,
    non-object-oriented fashion.
  • By forcing all programs into an object-oriented
    structure, benefits of OO are realized.
    (encapsulation, reusability)

22
Java is Network Savvy
  • The language provides a rich set of tools for
    programming across a network.
  • The Java standard library provides classes for
    describing universal resource locators (URLs) and
    for execution in controlled environments such as
    a World Wide Web browser.

23
Java is Interpreted
  • Java was designed for a multicomputer execution
    environment.
  • Any type of computer could be used as a Java
    virtual machine.
  • Java programs were compiled into bytecodes ,
    could be stored on any type of machine. An
    interpreter would read the bytecodes and execute
    them.
  • Interpreters are much slower in execution.
  • A just-in-time (JIT) compiler is a system that
    read machine-independent bytecode and translates
    them into actual machine instructions.

24
Java is Robust
  • The Java language and associated libraries are
    designed to be graceful in the presence of
    hardware and software errors.
  • The use of exception handling.
  • Programmers are forced into thinking about
    potential source of errors.
  • Java has an automatic memory management, garbage
    collection.
  • It detects and recovers memory that is no longer
    being used by the current running program.

25
Java is Secure
  • Multi-level Security System
  • First Level
  • Eliminating pointers remove the most common
    errors.
  • The Java language insists that array index values
    are cheked before the are referenced.
  • All variables must be assigned values before
    being used.
  • Second Level
  • Bytecodes are checked for common errors.
  • Such as they do not access classes incorrectly,
    overflow or underflow the operand stack, or use
    illegal data conversions
  • Java programs are restricted in the type of
    operations they can perform.
  • When they execute a program brought over the
    network, their local computers are safe from
    tampering.

26
Java is Architecture Neutral
  • Java bytecodes work with all machines.
  • A Java program is the same whether it runs on a
    PC. a Macintosh, or a Unix system.
  • C libraries differ from one platform to
    another.
  • Thus, it is difficult to move programs designed
    for the PC onto a Macintosh.
  • Java hides these application-specific details
    under a layer of abstraction in the standard Java
    library.

27
Java is Portable
  • Java programs are portable because the Java
    library hides architecture-specific concepts and
    bytecodes are the same for all machines.
  • The exact same program can be compiled on one
    system, then executed on many different types of
    systems.

28
Java is High-performance
  • Just-in-time compilers allow platform-dependent
    Java programs to be executed with nearly the same
    run-time performance as conventional compiled
    languages.

29
Java is Multithreaded
  • Java is one of the first languages to be designed
    for multiple threads of execution running in one
    program.
  • It is easy to set up multitasking.
  • The coordination of these parallel processes is
    also relatively simple.

30
Java is Dynamic
  • Because Java programs move across the Internet
    and execute on the users local computer, they
    permit a degree of dynamic behaviors impossible
    in older style systems.
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