working of Java Programs

A Little Terminology

Keep in mind that I am assuming that you know nothing about programming. Here are several vocabulary terms that will make things understandable:

• Computer program - A computer program is a set of instructions that tell a computer exactly what to do. The instructions might tell the computer to add up a set of numbers, or compare two numbers and make a decision based on the result, or whatever. But a computer program is simply a set of instructions for the computer, like a recipe is a set of instructions for a cook or musical notes are a set of instructions for a musician. The computer follows your instructions exactly and in the process does something useful -- like balancing a checkbook or displaying a game on the screen or implementing a word processor.
• Programming language - In order for a computer to recognize the instructions you give it, those instructions need to be written in a language the computer understands -- a programming language. There are many computer programming languages -- Fortran, Cobol, Basic, Pascal, C, C++, Java, Perl -- just like there are many spoken languages. They all express approximately the same concepts in different ways.
• Compiler - A compiler translates a computer program written in a human-readable computer language (like Java) into a form that a computer can execute. You have probably seen EXE files on your computer. These EXE files are the output of compilers. They contain executables -- machine-readable programs translated from human-readable programs.

In order for you to start writing computer programs in a programming language called Java, you need a compiler for the Java language. The next section guides you through the process of downloading and installing a compiler. Once you have a compiler, we can get started. This process is going to take several hours, much of that time being download time for several large files. You are also going to need about 40 megabytes of free disk space (make sure you have the space available before you get started).

Downloading the Java Compiler

In order to get a Java development environment set up on your machine -- you "develop" (write) computer programs using a "development environment" -- you will have to complete the following steps:

1. Download a large file containing the Java development environment (the compiler and other tools).
2. Download a large file containing the Java documentation.
3. If you do not already have WinZip (or an equivalent) on your machine, you will need to download a large file containing WinZip and install it.
4. Install the Java development environment.
5. Install the documentation.
6. Adjust several environment variables.
7. Test everything out. 

Wi-Max

           Over the past decade, internet has grown rapidly and become extremely popular, especially when the world is entering the digital age. 

           You can access the internet through dial-up service (dial up), wi-fi and broadband (broad-band). Dial-up is outdated, is still popular but broad-band service charge is not cheap wi-fi is also limited in coverage. A new access protocol was established with the so-called WiMAX (Worldwide Interoperability for Mircrowave Access) deserves to replace all three methods. 

            A WiMAX system consists of base stations and receiving equipment (modem). The stations can connect to internet directly via broadband cable or using high-frequency radio waves (10GHz-65GHz) to communicate with each other. Coverage of approximately 8000 km2 each station (radius ~ 50 km) with access speed up to 70 Mbps, providing to the remote service high speed internet which are very cheap prices (due to charge line, including maintenance costs), the number of subscribers is much greater than the current service. With a mobile device (PDA, laptop, 3G Mobile Phone, ...) equipped with WiMAX equipment revenue, you can access the internet anywhere! To obtain high-frequency radio waves need huge antennas and power consumption should be communication between client devices and wave propagation using narrow frequency band (2GHz-11GHz).