Download Programming Languages Language Generations Computer

School of Computer Science &
Information Technology
Programming Languages
G6DICP - Lecture 2
The Java Programming Language

Formal languages in which computer programs are
written
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All languages consist of syntax and semantics
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Low level languages - close to machine code

High level languages - further removed from
machine code
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Language Generations
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Computer Programs
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First: Raw machine code
Second: Assembly language (NB processor dependent)
Third: High level languages (eg Java, C, Fortran, Cobol
etc)
Fourth: Application languages (eg SQL, Postcript
Fifth: AI languages (expert systems, fuzzy logic, neural
networks etc)
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Computers are "stupid"
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Mathematical and logical instructions are executed very quickly and
accurately.
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They obediently but stupidly do what you tell them to - not
necessarily what you want them to!
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Tiny errors in a program can cause major problems when it is
executed.
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Always remember syntax as well as semantics!
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Careful planning is essential
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Flow charts are a useful tool to represent program flow visually.
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Components of
Tea Making Program
Kettle-Boiling Program
Is Kettle full?
No
Fill Kettle
Fill Kettle
Yes
Boil Kettle
Place kettle
under tap
Place Kettle
on hob
Open tap
Turn on heat
Wait
Make Tea
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Wait
No
Boil Kettle
6
Is kettle full?
Is kettle boiling?
Yes
Close tap
Turn off heat
Yes
Kettle-Boiling Program
What is Java?
Fill Kettle
Place k ettle
u n d er tap
Is Kettle full?
No

O p en tap
Java is a programming language

Wait
No
Created by Sun Microsystems
Is k ettle fu ll?
Yes
Y es
Clo se tap
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B oil Kettle
Java is not only for web programming


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Place Kettle
on hob
Turn on heat
Wait
Is kettle
boiling?
Often used for web programming
Initially marketed as a web development system
General purpose programming language
Yes
Turn off heat

Very similar to C++ - simplified!
Make Tea
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Java Model
Features of Java
Byte Code
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Originally developed for hardware devices.
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Platform Independent Binaries
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Virtual Machine
Most operating systems
Also hardware devices
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Robust and easy to use
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Object Oriented and highly modular
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Internationalisation
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Networking and Security features
Operating System
Hardware
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Java VM Platforms
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Sun supported platforms
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Solaris
Win32 (Windows 95/98 & NT)
Linux
“Hardware”
Applications
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Other Unix
Mac OS
Palm OS
Symbian
and many others
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Delivered over the Internet
Require a Java capable WWW browser
Servlets
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Standalone programs
Require a VM
Applets
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Third party platforms (freely licensed)
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Types of Java Programs
Require a Java capable WWW server
Java Application
Java Applet
Storage
Source Code
Web Server
Byte Code
HTML
Byte Code
CPU/memory
Compiler
Web Browser
Web Browser
Program Execution
(embedded in web page)
Program Execution
Interpreter (VM)
Program Execution
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Flavours of Java
Development Software
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Java Developers Kit (JDK)
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Freely available from Sun for most platforms
“no frills” development
JavaScript
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Compiler - javac
Interpreter - java
Applet viewer - appletviewer
Utilities (auto-documentation, debugging, optimisation etc)
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This is not Java!
Java Versions
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Very obsolete
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JDK 1.0
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Java Runtime Environment (JRE)
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Obsolete
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Integrated Development Environments / RAD Systems
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Java 2
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Third party VM’s
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JDK 1.1
JDK 1.2, 1.3 & 1.4