CTG - Java Background

Overview
  [Supercomputing]
  [Project Development]
  [Project Design]

Login Procedure
  [ssh (Putty) ]
  [Tutorial]

Unix
  [Basic Commands]
  [Utilities]
  [Pico]
  [Cygwin]

C++
  [Background]
  [Tutorial]
  [Advanced Syntax]

Java
  [Background]
  [Tutorial - Unix]
  [Tutorial - PC]
  [Advanced Syntax]

Graphics
  [gnuplot]
  [Tutorial]

Extras
  [Cygwin-X11]
  [E-mail]
  [ftp]
  [HTML]
  [Resources]

Supercomputing Challenge
  [Home Page]
  [Technical Guide]

History: Sun Microsystems originally created a small language called "Oak" to be used in devices such as microwave ovens. Eventually, they realized they had a considerably more diverse and robust languange in Oak. Soonafter they renamed it "Java", and started to market it as a general purpose programming language.

Note that Java has nothing to do with a language called "JavaScript". JavaScript is a scripting language created by Netscape to be used as an additon to HTML. It was originally called "LiveScript", and the name change was a marketing ploy to redirect some of the "buzz" centered around Java towards JavaScript.

Java has been considered the forerunner to replace C++ as the most widely used programming language. This is in no small part due to the relative ease with which Java can create GUIs (Graphical User Interfaces).

The Programming Language: To write any program, you must either understand the machine code of your computer, or use a "high level" language such as Java. With these higher level languages we start by using a text editor (such as pico) to enter our program into a file. This file, which is in English words and phrases, must then be changed into "machine code" a language which can be best described as ones and zeros. This is the language computers really understand, not English (or Spanish, or French, etc.)

To get this machine code, we first convert the original file into "bytecodes" by "compiling" the source code. You compile code by typing "javac" (no quotes) followed by the source file name. The compiler will create an executable file with the same name as the source code and a ".class" extension.

A software package called the Java Virtual Machine (JVM), then converts the file with bytecodes into machine code during program execution. You invoke the JVM by typing "java" (no quotes) followed by the first part of the executable file name (i.e. without the ".java" extension).


Supercomputing ChallengeQuestions? e-mail: consult